/*

 ** 2001 September 15

 **

 ** The author disclaims copyright to this source code.  In place of

 ** a legal notice, here is a blessing:

 **

 **    May you do good and not evil.

 **    May you find forgiveness for yourself and forgive others.

 **    May you share freely, never taking more than you give.

 **

 *************************************************************************

 ** This file contains routines used for analyzing expressions and

 ** for generating VDBE code that evaluates expressions in SQLite.

 **

 ** $Id: expr.c,v 1.387 2008/07/28 19:34:53 drh Exp $

 */

 #include "sqliteInt.h"

 #include <ctype.h>

 /*

 ** Return the 'affinity' of the expression pExpr if any.

 **

 ** If pExpr is a column, a reference to a column via an 'AS' alias,

 ** or a sub-select with a column as the return value, then the 

 ** affinity of that column is returned. Otherwise, 0x00 is returned,

 ** indicating no affinity for the expression.

 **

 ** i.e. the WHERE clause expresssions in the following statements all

 ** have an affinity:

 **

 ** CREATE TABLE t1(a);

 ** SELECT * FROM t1 WHERE a;

 ** SELECT a AS b FROM t1 WHERE b;

 ** SELECT * FROM t1 WHERE (select a from t1);

 */

 char sqlite3ExprAffinity(Expr *pExpr){

   int op = pExpr->op;

   if( op==TK_SELECT ){

     return sqlite3ExprAffinity(pExpr->pSelect->pEList->a[0].pExpr);

   }

 #ifndef SQLITE_OMIT_CAST

   if( op==TK_CAST ){

     return sqlite3AffinityType(&pExpr->token);

   }

 #endif

   return pExpr->affinity;

 }

 /*

 ** Set the collating sequence for expression pExpr to be the collating

 ** sequence named by pToken.   Return a pointer to the revised expression.

 ** The collating sequence is marked as "explicit" using the EP_ExpCollate

 ** flag.  An explicit collating sequence will override implicit

 ** collating sequences.

 */

 Expr *sqlite3ExprSetColl(Parse *pParse, Expr *pExpr, Token *pName){

   char *zColl = 0;            /* Dequoted name of collation sequence */

   CollSeq *pColl;

   sqlite3 *db = pParse->db;

   zColl = sqlite3NameFromToken(db, pName);

   if( pExpr && zColl ){

     pColl = sqlite3LocateCollSeq(pParse, zColl, -1);

     if( pColl ){

       pExpr->pColl = pColl;

       pExpr->flags |= EP_ExpCollate;

     }

   }

   sqlite3DbFree(db, zColl);

   return pExpr;

 }

 /*

 ** Return the default collation sequence for the expression pExpr. If

 ** there is no default collation type, return 0.

 */

 CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr){

   CollSeq *pColl = 0;

   if( pExpr ){

     int op;

     pColl = pExpr->pColl;

     op = pExpr->op;

     if( (op==TK_CAST || op==TK_UPLUS) && !pColl ){

       return sqlite3ExprCollSeq(pParse, pExpr->pLeft);

     }

   }

   if( sqlite3CheckCollSeq(pParse, pColl) ){ 

     pColl = 0;

   }

   return pColl;

 }

 /*

 ** pExpr is an operand of a comparison operator.  aff2 is the

 ** type affinity of the other operand.  This routine returns the

 ** type affinity that should be used for the comparison operator.

 */

 char sqlite3CompareAffinity(Expr *pExpr, char aff2){

   char aff1 = sqlite3ExprAffinity(pExpr);

   if( aff1 && aff2 ){

     /* Both sides of the comparison are columns. If one has numeric

     ** affinity, use that. Otherwise use no affinity.

     */

     if( sqlite3IsNumericAffinity(aff1) || sqlite3IsNumericAffinity(aff2) ){

       return SQLITE_AFF_NUMERIC;

     }else{

       return SQLITE_AFF_NONE;

     }

   }else if( !aff1 && !aff2 ){

     /* Neither side of the comparison is a column.  Compare the

     ** results directly.

     */

     return SQLITE_AFF_NONE;

   }else{

     /* One side is a column, the other is not. Use the columns affinity. */

     assert( aff1==0 || aff2==0 );

     return (aff1 + aff2);

   }

 }

 /*

 ** pExpr is a comparison operator.  Return the type affinity that should

 ** be applied to both operands prior to doing the comparison.

 */

 static char comparisonAffinity(Expr *pExpr){

   char aff;

   assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||

           pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||

           pExpr->op==TK_NE );

   assert( pExpr->pLeft );

   aff = sqlite3ExprAffinity(pExpr->pLeft);

   if( pExpr->pRight ){

     aff = sqlite3CompareAffinity(pExpr->pRight, aff);

   }

   else if( pExpr->pSelect ){

     aff = sqlite3CompareAffinity(pExpr->pSelect->pEList->a[0].pExpr, aff);

   }

   else if( !aff ){

     aff = SQLITE_AFF_NONE;

   }

   return aff;

 }

 /*

 ** pExpr is a comparison expression, eg. '=', '<', IN(...) etc.

 ** idx_affinity is the affinity of an indexed column. Return true

 ** if the index with affinity idx_affinity may be used to implement

 ** the comparison in pExpr.

 */

 int sqlite3IndexAffinityOk(Expr *pExpr, char idx_affinity){

   char aff = comparisonAffinity(pExpr);

   switch( aff ){

     case SQLITE_AFF_NONE:

       return 1;

     case SQLITE_AFF_TEXT:

       return idx_affinity==SQLITE_AFF_TEXT;

     default:

       return sqlite3IsNumericAffinity(idx_affinity);

   }

 }

 /*

 ** Return the P5 value that should be used for a binary comparison

 ** opcode (OP_Eq, OP_Ge etc.) used to compare pExpr1 and pExpr2.

 */

 static u8 binaryCompareP5(Expr *pExpr1, Expr *pExpr2, int jumpIfNull){

   u8 aff = (char)sqlite3ExprAffinity(pExpr2);

   aff = sqlite3CompareAffinity(pExpr1, aff) | jumpIfNull;

   return aff;

 }

 /*

 ** Return a pointer to the collation sequence that should be used by

 ** a binary comparison operator comparing pLeft and pRight.

 **

 ** If the left hand expression has a collating sequence type, then it is

 ** used. Otherwise the collation sequence for the right hand expression

 ** is used, or the default (BINARY) if neither expression has a collating

 ** type.

 **

 ** Argument pRight (but not pLeft) may be a null pointer. In this case,

 ** it is not considered.

 */

 CollSeq *sqlite3BinaryCompareCollSeq(

   Parse *pParse, 

   Expr *pLeft, 

   Expr *pRight

 ){

   CollSeq *pColl;

   assert( pLeft );

   if( pLeft->flags & EP_ExpCollate ){

     assert( pLeft->pColl );

     pColl = pLeft->pColl;

   }else if( pRight && pRight->flags & EP_ExpCollate ){

     assert( pRight->pColl );

     pColl = pRight->pColl;

   }else{

     pColl = sqlite3ExprCollSeq(pParse, pLeft);

     if( !pColl ){

       pColl = sqlite3ExprCollSeq(pParse, pRight);

     }

   }

   return pColl;

 }

 /*

 ** Generate the operands for a comparison operation.  Before

 ** generating the code for each operand, set the EP_AnyAff

 ** flag on the expression so that it will be able to used a

 ** cached column value that has previously undergone an

 ** affinity change.

 */

 static void codeCompareOperands(

   Parse *pParse,    /* Parsing and code generating context */

   Expr *pLeft,      /* The left operand */

   int *pRegLeft,    /* Register where left operand is stored */

   int *pFreeLeft,   /* Free this register when done */

   Expr *pRight,     /* The right operand */

   int *pRegRight,   /* Register where right operand is stored */

   int *pFreeRight   /* Write temp register for right operand there */

 ){

   while( pLeft->op==TK_UPLUS ) pLeft = pLeft->pLeft;

   pLeft->flags |= EP_AnyAff;

   *pRegLeft = sqlite3ExprCodeTemp(pParse, pLeft, pFreeLeft);

   while( pRight->op==TK_UPLUS ) pRight = pRight->pLeft;

   pRight->flags |= EP_AnyAff;

   *pRegRight = sqlite3ExprCodeTemp(pParse, pRight, pFreeRight);

 }

 /*

 ** Generate code for a comparison operator.

 */

 static int codeCompare(

   Parse *pParse,    /* The parsing (and code generating) context */

   Expr *pLeft,      /* The left operand */

   Expr *pRight,     /* The right operand */

   int opcode,       /* The comparison opcode */

   int in1, int in2, /* Register holding operands */

   int dest,         /* Jump here if true.  */

   int jumpIfNull    /* If true, jump if either operand is NULL */

 ){

   int p5;

   int addr;

   CollSeq *p4;

   p4 = sqlite3BinaryCompareCollSeq(pParse, pLeft, pRight);

   p5 = binaryCompareP5(pLeft, pRight, jumpIfNull);

   addr = sqlite3VdbeAddOp4(pParse->pVdbe, opcode, in2, dest, in1,

                            (void*)p4, P4_COLLSEQ);

   sqlite3VdbeChangeP5(pParse->pVdbe, p5);

   if( (p5 & SQLITE_AFF_MASK)!=SQLITE_AFF_NONE ){

     sqlite3ExprCacheAffinityChange(pParse, in1, 1);

     sqlite3ExprCacheAffinityChange(pParse, in2, 1);

   }

   return addr;

 }

 #if SQLITE_MAX_EXPR_DEPTH>0

 /*

 ** Check that argument nHeight is less than or equal to the maximum

 ** expression depth allowed. If it is not, leave an error message in

 ** pParse.

 */

 static int checkExprHeight(Parse *pParse, int nHeight){

   int rc = SQLITE_OK;

   int mxHeight = pParse->db->aLimit[SQLITE_LIMIT_EXPR_DEPTH];

   if( nHeight>mxHeight ){

     sqlite3ErrorMsg(pParse, 

        "Expression tree is too large (maximum depth %d)", mxHeight

     );

     rc = SQLITE_ERROR;

   }

   return rc;

 }

 /* The following three functions, heightOfExpr(), heightOfExprList()

 ** and heightOfSelect(), are used to determine the maximum height

 ** of any expression tree referenced by the structure passed as the

 ** first argument.

 **

 ** If this maximum height is greater than the current value pointed

 ** to by pnHeight, the second parameter, then set *pnHeight to that

 ** value.

 */

 static void heightOfExpr(Expr *p, int *pnHeight){

   if( p ){

     if( p->nHeight>*pnHeight ){

       *pnHeight = p->nHeight;

     }

   }

 }

 static void heightOfExprList(ExprList *p, int *pnHeight){

   if( p ){

     int i;

     for(i=0; i<p->nExpr; i++){

       heightOfExpr(p->a[i].pExpr, pnHeight);

     }

   }

 }

 static void heightOfSelect(Select *p, int *pnHeight){

   if( p ){

     heightOfExpr(p->pWhere, pnHeight);

     heightOfExpr(p->pHaving, pnHeight);

     heightOfExpr(p->pLimit, pnHeight);

     heightOfExpr(p->pOffset, pnHeight);

     heightOfExprList(p->pEList, pnHeight);

     heightOfExprList(p->pGroupBy, pnHeight);

     heightOfExprList(p->pOrderBy, pnHeight);

     heightOfSelect(p->pPrior, pnHeight);

   }

 }

 /*

 ** Set the Expr.nHeight variable in the structure passed as an 

 ** argument. An expression with no children, Expr.pList or 

 ** Expr.pSelect member has a height of 1. Any other expression

 ** has a height equal to the maximum height of any other 

 ** referenced Expr plus one.

 */

 static void exprSetHeight(Expr *p){

   int nHeight = 0;

   heightOfExpr(p->pLeft, &nHeight);

   heightOfExpr(p->pRight, &nHeight);

   heightOfExprList(p->pList, &nHeight);

   heightOfSelect(p->pSelect, &nHeight);

   p->nHeight = nHeight + 1;

 }

 /*

 ** Set the Expr.nHeight variable using the exprSetHeight() function. If

 ** the height is greater than the maximum allowed expression depth,

 ** leave an error in pParse.

 */

 void sqlite3ExprSetHeight(Parse *pParse, Expr *p){

   exprSetHeight(p);

   checkExprHeight(pParse, p->nHeight);

 }

 /*

 ** Return the maximum height of any expression tree referenced

 ** by the select statement passed as an argument.

 */

 int sqlite3SelectExprHeight(Select *p){

   int nHeight = 0;

   heightOfSelect(p, &nHeight);

   return nHeight;

 }

 #else

   #define checkExprHeight(x,y)

   #define exprSetHeight(y)

 #endif /* SQLITE_MAX_EXPR_DEPTH>0 */

 /*

 ** Construct a new expression node and return a pointer to it.  Memory

 ** for this node is obtained from sqlite3_malloc().  The calling function

 ** is responsible for making sure the node eventually gets freed.

 */

 Expr *sqlite3Expr(

   sqlite3 *db,            /* Handle for sqlite3DbMallocZero() (may be null) */

   int op,                 /* Expression opcode */

   Expr *pLeft,            /* Left operand */

   Expr *pRight,           /* Right operand */

   const Token *pToken     /* Argument token */

 ){

   Expr *pNew;

   pNew = sqlite3DbMallocZero(db, sizeof(Expr));

   if( pNew==0 ){

     /* When malloc fails, delete pLeft and pRight. Expressions passed to 

     ** this function must always be allocated with sqlite3Expr() for this 

     ** reason. 

     */

     sqlite3ExprDelete(db, pLeft);

     sqlite3ExprDelete(db, pRight);

     return 0;

   }

   pNew->op = op;

   pNew->pLeft = pLeft;

   pNew->pRight = pRight;

   pNew->iAgg = -1;

   pNew->span.z = (u8*)"";

   if( pToken ){

     assert( pToken->dyn==0 );

     pNew->span = pNew->token = *pToken;

   }else if( pLeft ){

     if( pRight ){

       if( pRight->span.dyn==0 && pLeft->span.dyn==0 ){

         sqlite3ExprSpan(pNew, &pLeft->span, &pRight->span);

       }

       if( pRight->flags & EP_ExpCollate ){

         pNew->flags |= EP_ExpCollate;

         pNew->pColl = pRight->pColl;

       }

     }

     if( pLeft->flags & EP_ExpCollate ){

       pNew->flags |= EP_ExpCollate;

       pNew->pColl = pLeft->pColl;

     }

   }

   exprSetHeight(pNew);

   return pNew;

 }

 /*

 ** Works like sqlite3Expr() except that it takes an extra Parse*

 ** argument and notifies the associated connection object if malloc fails.

 */

 Expr *sqlite3PExpr(

   Parse *pParse,          /* Parsing context */

   int op,                 /* Expression opcode */

   Expr *pLeft,            /* Left operand */

   Expr *pRight,           /* Right operand */

   const Token *pToken     /* Argument token */

 ){

   Expr *p = sqlite3Expr(pParse->db, op, pLeft, pRight, pToken);

   if( p ){

     checkExprHeight(pParse, p->nHeight);

   }

   return p;

 }

 /*

 ** When doing a nested parse, you can include terms in an expression

 ** that look like this:   #1 #2 ...  These terms refer to registers

 ** in the virtual machine.  #N is the N-th register.

 **

 ** This routine is called by the parser to deal with on of those terms.

 ** It immediately generates code to store the value in a memory location.

 ** The returns an expression that will code to extract the value from

 ** that memory location as needed.

 */

 Expr *sqlite3RegisterExpr(Parse *pParse, Token *pToken){

   Vdbe *v = pParse->pVdbe;

   Expr *p;

   if( pParse->nested==0 ){

     sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", pToken);

     return sqlite3PExpr(pParse, TK_NULL, 0, 0, 0);

   }

   if( v==0 ) return 0;

   p = sqlite3PExpr(pParse, TK_REGISTER, 0, 0, pToken);

   if( p==0 ){

     return 0;  /* Malloc failed */

   }

   p->iTable = atoi((char*)&pToken->z[1]);

   return p;

 }

 /*

 ** Join two expressions using an AND operator.  If either expression is

 ** NULL, then just return the other expression.

 */

 Expr *sqlite3ExprAnd(sqlite3 *db, Expr *pLeft, Expr *pRight){

   if( pLeft==0 ){

     return pRight;

   }else if( pRight==0 ){

     return pLeft;

   }else{

     return sqlite3Expr(db, TK_AND, pLeft, pRight, 0);

   }

 }

 /*

 ** Set the Expr.span field of the given expression to span all

 ** text between the two given tokens.  Both tokens must be pointing

 ** at the same string.

 */

 void sqlite3ExprSpan(Expr *pExpr, Token *pLeft, Token *pRight){

   assert( pRight!=0 );

   assert( pLeft!=0 );

   if( pExpr ){

     pExpr->span.z = pLeft->z;

     pExpr->span.n = pRight->n + (pRight->z - pLeft->z);

   }

 }

 /*

 ** Construct a new expression node for a function with multiple

 ** arguments.

 */

 Expr *sqlite3ExprFunction(Parse *pParse, ExprList *pList, Token *pToken){

   Expr *pNew;

   sqlite3 *db = pParse->db;

   assert( pToken );

   pNew = sqlite3DbMallocZero(db, sizeof(Expr) );

   if( pNew==0 ){

     sqlite3ExprListDelete(db, pList); /* Avoid leaking memory when malloc fails */

     return 0;

   }

   pNew->op = TK_FUNCTION;

   pNew->pList = pList;

   assert( pToken->dyn==0 );

   pNew->token = *pToken;

   pNew->span = pNew->token;

   sqlite3ExprSetHeight(pParse, pNew);

   return pNew;

 }

 /*

 ** Assign a variable number to an expression that encodes a wildcard

 ** in the original SQL statement.  

 **

 ** Wildcards consisting of a single "?" are assigned the next sequential

 ** variable number.

 **

 ** Wildcards of the form "?nnn" are assigned the number "nnn".  We make

 ** sure "nnn" is not too be to avoid a denial of service attack when

 ** the SQL statement comes from an external source.

 **

 ** Wildcards of the form ":aaa" or "$aaa" are assigned the same number

 ** as the previous instance of the same wildcard.  Or if this is the first

 ** instance of the wildcard, the next sequenial variable number is

 ** assigned.

 */

 void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr){

   Token *pToken;

   sqlite3 *db = pParse->db;

   if( pExpr==0 ) return;

   pToken = &pExpr->token;

   assert( pToken->n>=1 );

   assert( pToken->z!=0 );

   assert( pToken->z[0]!=0 );

   if( pToken->n==1 ){

     /* Wildcard of the form "?".  Assign the next variable number */

     pExpr->iTable = ++pParse->nVar;

   }else if( pToken->z[0]=='?' ){

     /* Wildcard of the form "?nnn".  Convert "nnn" to an integer and

     ** use it as the variable number */

     int i;

     pExpr->iTable = i = atoi((char*)&pToken->z[1]);

     testcase( i==0 );

     testcase( i==1 );

     testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]-1 );

     testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] );

     if( i<1 || i>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){

       sqlite3ErrorMsg(pParse, "variable number must be between ?1 and ?%d",

           db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]);

     }

     if( i>pParse->nVar ){

       pParse->nVar = i;

     }

   }else{

     /* Wildcards of the form ":aaa" or "$aaa".  Reuse the same variable

     ** number as the prior appearance of the same name, or if the name

     ** has never appeared before, reuse the same variable number

     */

     int i, n;

     n = pToken->n;

     for(i=0; i<pParse->nVarExpr; i++){

       Expr *pE;

       if( (pE = pParse->apVarExpr[i])!=0

           && pE->token.n==n

           && memcmp(pE->token.z, pToken->z, n)==0 ){

         pExpr->iTable = pE->iTable;

         break;

       }

     }

     if( i>=pParse->nVarExpr ){

       pExpr->iTable = ++pParse->nVar;

       if( pParse->nVarExpr>=pParse->nVarExprAlloc-1 ){

         pParse->nVarExprAlloc += pParse->nVarExprAlloc + 10;

         pParse->apVarExpr =

             sqlite3DbReallocOrFree(

               db,

               pParse->apVarExpr,

               pParse->nVarExprAlloc*sizeof(pParse->apVarExpr[0])

             );

       }

       if( !db->mallocFailed ){

         assert( pParse->apVarExpr!=0 );

         pParse->apVarExpr[pParse->nVarExpr++] = pExpr;

       }

     }

   } 

   if( !pParse->nErr && pParse->nVar>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){

     sqlite3ErrorMsg(pParse, "too many SQL variables");

   }

 }

 /*

 ** Recursively delete an expression tree.

 */

 void sqlite3ExprDelete(sqlite3 *db, Expr *p){

   if( p==0 ) return;

   if( p->span.dyn ) sqlite3DbFree(db, (char*)p->span.z);

   if( p->token.dyn ) sqlite3DbFree(db, (char*)p->token.z);

   sqlite3ExprDelete(db, p->pLeft);

   sqlite3ExprDelete(db, p->pRight);

   sqlite3ExprListDelete(db, p->pList);

   sqlite3SelectDelete(db, p->pSelect);

   sqlite3DbFree(db, p);

 }

 /*

 ** The Expr.token field might be a string literal that is quoted.

 ** If so, remove the quotation marks.

 */

 void sqlite3DequoteExpr(sqlite3 *db, Expr *p){

   if( ExprHasAnyProperty(p, EP_Dequoted) ){

     return;

   }

   ExprSetProperty(p, EP_Dequoted);

   if( p->token.dyn==0 ){

     sqlite3TokenCopy(db, &p->token, &p->token);

   }

   sqlite3Dequote((char*)p->token.z);

 }

 /*

 ** The following group of routines make deep copies of expressions,

 ** expression lists, ID lists, and select statements.  The copies can

 ** be deleted (by being passed to their respective ...Delete() routines)

 ** without effecting the originals.

 **

 ** The expression list, ID, and source lists return by sqlite3ExprListDup(),

 ** sqlite3IdListDup(), and sqlite3SrcListDup() can not be further expanded 

 ** by subsequent calls to sqlite*ListAppend() routines.

 **

 ** Any tables that the SrcList might point to are not duplicated.

 */

 Expr *sqlite3ExprDup(sqlite3 *db, Expr *p){

   Expr *pNew;

   if( p==0 ) return 0;

   pNew = sqlite3DbMallocRaw(db, sizeof(*p) );

   if( pNew==0 ) return 0;

   memcpy(pNew, p, sizeof(*pNew));

   if( p->token.z!=0 ){

     pNew->token.z = (u8*)sqlite3DbStrNDup(db, (char*)p->token.z, p->token.n);

     pNew->token.dyn = 1;

   }else{

     assert( pNew->token.z==0 );

   }

   pNew->span.z = 0;

   pNew->pLeft = sqlite3ExprDup(db, p->pLeft);

   pNew->pRight = sqlite3ExprDup(db, p->pRight);

   pNew->pList = sqlite3ExprListDup(db, p->pList);

   pNew->pSelect = sqlite3SelectDup(db, p->pSelect);

   return pNew;

 }

 void sqlite3TokenCopy(sqlite3 *db, Token *pTo, Token *pFrom){

   if( pTo->dyn ) sqlite3DbFree(db, (char*)pTo->z);

   if( pFrom->z ){

     pTo->n = pFrom->n;

     pTo->z = (u8*)sqlite3DbStrNDup(db, (char*)pFrom->z, pFrom->n);

     pTo->dyn = 1;

   }else{

     pTo->z = 0;

   }

 }

 ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p){

   ExprList *pNew;

   struct ExprList_item *pItem, *pOldItem;

   int i;

   if( p==0 ) return 0;

   pNew = sqlite3DbMallocRaw(db, sizeof(*pNew) );

   if( pNew==0 ) return 0;

   pNew->iECursor = 0;

   pNew->nExpr = pNew->nAlloc = p->nExpr;

   pNew->a = pItem = sqlite3DbMallocRaw(db,  p->nExpr*sizeof(p->a[0]) );

   if( pItem==0 ){

     sqlite3DbFree(db, pNew);

     return 0;

   } 

   pOldItem = p->a;

   for(i=0; i<p->nExpr; i++, pItem++, pOldItem++){

     Expr *pNewExpr, *pOldExpr;

     pItem->pExpr = pNewExpr = sqlite3ExprDup(db, pOldExpr = pOldItem->pExpr);

     if( pOldExpr->span.z!=0 && pNewExpr ){

       /* Always make a copy of the span for top-level expressions in the

       ** expression list.  The logic in SELECT processing that determines

       ** the names of columns in the result set needs this information */

       sqlite3TokenCopy(db, &pNewExpr->span, &pOldExpr->span);

     }

     assert( pNewExpr==0 || pNewExpr->span.z!=0 

             || pOldExpr->span.z==0

             || db->mallocFailed );

     pItem->zName = sqlite3DbStrDup(db, pOldItem->zName);

     pItem->sortOrder = pOldItem->sortOrder;

     pItem->isAgg = pOldItem->isAgg;

     pItem->done = 0;

   }

   return pNew;

 }

 /*

 ** If cursors, triggers, views and subqueries are all omitted from

 ** the build, then none of the following routines, except for 

 ** sqlite3SelectDup(), can be called. sqlite3SelectDup() is sometimes

 ** called with a NULL argument.

 */

 #if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER) \

  || !defined(SQLITE_OMIT_SUBQUERY)

 SrcList *sqlite3SrcListDup(sqlite3 *db, SrcList *p){

   SrcList *pNew;

   int i;

   int nByte;

   if( p==0 ) return 0;

   nByte = sizeof(*p) + (p->nSrc>0 ? sizeof(p->a[0]) * (p->nSrc-1) : 0);

   pNew = sqlite3DbMallocRaw(db, nByte );

   if( pNew==0 ) return 0;

   pNew->nSrc = pNew->nAlloc = p->nSrc;

   for(i=0; i<p->nSrc; i++){

     struct SrcList_item *pNewItem = &pNew->a[i];

     struct SrcList_item *pOldItem = &p->a[i];

     Table *pTab;

     pNewItem->zDatabase = sqlite3DbStrDup(db, pOldItem->zDatabase);

     pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);

     pNewItem->zAlias = sqlite3DbStrDup(db, pOldItem->zAlias);

     pNewItem->jointype = pOldItem->jointype;

     pNewItem->iCursor = pOldItem->iCursor;

     pNewItem->isPopulated = pOldItem->isPopulated;

     pTab = pNewItem->pTab = pOldItem->pTab;

     if( pTab ){

       pTab->nRef++;

     }

     pNewItem->pSelect = sqlite3SelectDup(db, pOldItem->pSelect);

     pNewItem->pOn = sqlite3ExprDup(db, pOldItem->pOn);

     pNewItem->pUsing = sqlite3IdListDup(db, pOldItem->pUsing);

     pNewItem->colUsed = pOldItem->colUsed;

   }

   return pNew;

 }

 IdList *sqlite3IdListDup(sqlite3 *db, IdList *p){

   IdList *pNew;

   int i;

   if( p==0 ) return 0;

   pNew = sqlite3DbMallocRaw(db, sizeof(*pNew) );

   if( pNew==0 ) return 0;

   pNew->nId = pNew->nAlloc = p->nId;

   pNew->a = sqlite3DbMallocRaw(db, p->nId*sizeof(p->a[0]) );

   if( pNew->a==0 ){

     sqlite3DbFree(db, pNew);

     return 0;

   }

   for(i=0; i<p->nId; i++){

     struct IdList_item *pNewItem = &pNew->a[i];

     struct IdList_item *pOldItem = &p->a[i];

     pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);

     pNewItem->idx = pOldItem->idx;

   }

   return pNew;

 }

 Select *sqlite3SelectDup(sqlite3 *db, Select *p){

   Select *pNew;

   if( p==0 ) return 0;

   pNew = sqlite3DbMallocRaw(db, sizeof(*p) );

   if( pNew==0 ) return 0;

   pNew->isDistinct = p->isDistinct;

   pNew->pEList = sqlite3ExprListDup(db, p->pEList);

   pNew->pSrc = sqlite3SrcListDup(db, p->pSrc);

   pNew->pWhere = sqlite3ExprDup(db, p->pWhere);

   pNew->pGroupBy = sqlite3ExprListDup(db, p->pGroupBy);

   pNew->pHaving = sqlite3ExprDup(db, p->pHaving);

   pNew->pOrderBy = sqlite3ExprListDup(db, p->pOrderBy);

   pNew->op = p->op;

   pNew->pPrior = sqlite3SelectDup(db, p->pPrior);

   pNew->pLimit = sqlite3ExprDup(db, p->pLimit);

   pNew->pOffset = sqlite3ExprDup(db, p->pOffset);

   pNew->iLimit = 0;

   pNew->iOffset = 0;

   pNew->isResolved = p->isResolved;

   pNew->isAgg = p->isAgg;

   pNew->usesEphm = 0;

   pNew->disallowOrderBy = 0;

   pNew->pRightmost = 0;

   pNew->addrOpenEphm[0] = -1;

   pNew->addrOpenEphm[1] = -1;

   pNew->addrOpenEphm[2] = -1;

   return pNew;

 }

 #else

 Select *sqlite3SelectDup(sqlite3 *db, Select *p){

   assert( p==0 );

   return 0;

 }

 #endif

 /*

 ** Add a new element to the end of an expression list.  If pList is

 ** initially NULL, then create a new expression list.

 */

 ExprList *sqlite3ExprListAppend(

   Parse *pParse,          /* Parsing context */

   ExprList *pList,        /* List to which to append. Might be NULL */

   Expr *pExpr,            /* Expression to be appended */

   Token *pName            /* AS keyword for the expression */

 ){

   sqlite3 *db = pParse->db;

   if( pList==0 ){

     pList = sqlite3DbMallocZero(db, sizeof(ExprList) );

     if( pList==0 ){

       goto no_mem;

     }

     assert( pList->nAlloc==0 );

   }

   if( pList->nAlloc<=pList->nExpr ){

     struct ExprList_item *a;

     int n = pList->nAlloc*2 + 4;

     a = sqlite3DbRealloc(db, pList->a, n*sizeof(pList->a[0]));

     if( a==0 ){

       goto no_mem;

     }

     pList->a = a;

     pList->nAlloc = n;

   }

   assert( pList->a!=0 );

   if( pExpr || pName ){

     struct ExprList_item *pItem = &pList->a[pList->nExpr++];

     memset(pItem, 0, sizeof(*pItem));

     pItem->zName = sqlite3NameFromToken(db, pName);

     pItem->pExpr = pExpr;

   }

   return pList;

 no_mem:     

   /* Avoid leaking memory if malloc has failed. */

   sqlite3ExprDelete(db, pExpr);

   sqlite3ExprListDelete(db, pList);

   return 0;

 }

 /*

 ** If the expression list pEList contains more than iLimit elements,

 ** leave an error message in pParse.

 */

 void sqlite3ExprListCheckLength(

   Parse *pParse,

   ExprList *pEList,

   const char *zObject

 ){

   int mx = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];

   testcase( pEList && pEList->nExpr==mx );

   testcase( pEList && pEList->nExpr==mx+1 );

   if( pEList && pEList->nExpr>mx ){

     sqlite3ErrorMsg(pParse, "too many columns in %s", zObject);

   }

 }

 /*

 ** Delete an entire expression list.

 */

 void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){

   int i;

   struct ExprList_item *pItem;

   if( pList==0 ) return;

   assert( pList->a!=0 || (pList->nExpr==0 && pList->nAlloc==0) );

   assert( pList->nExpr<=pList->nAlloc );

   for(pItem=pList->a, i=0; i<pList->nExpr; i++, pItem++){

     sqlite3ExprDelete(db, pItem->pExpr);

     sqlite3DbFree(db, pItem->zName);

   }

   sqlite3DbFree(db, pList->a);

   sqlite3DbFree(db, pList);

 }

 /*

 ** Walk an expression tree.  Call xFunc for each node visited.  xFunc

 ** is called on the node before xFunc is called on the nodes children.

 **

 ** The return value from xFunc determines whether the tree walk continues.

 ** 0 means continue walking the tree.  1 means do not walk children

 ** of the current node but continue with siblings.  2 means abandon

 ** the tree walk completely.

 **

 ** The return value from this routine is 1 to abandon the tree walk

 ** and 0 to continue.

 **

 ** NOTICE:  This routine does *not* descend into subqueries.

 */

 static int walkExprList(ExprList *, int (*)(void *, Expr*), void *);

 static int walkExprTree(Expr *pExpr, int (*xFunc)(void*,Expr*), void *pArg){

   int rc;

   if( pExpr==0 ) return 0;

   rc = (*xFunc)(pArg, pExpr);

   if( rc==0 ){

     if( walkExprTree(pExpr->pLeft, xFunc, pArg) ) return 1;

     if( walkExprTree(pExpr->pRight, xFunc, pArg) ) return 1;

     if( walkExprList(pExpr->pList, xFunc, pArg) ) return 1;

   }

   return rc>1;

 }

 /*

 ** Call walkExprTree() for every expression in list p.

 */

 static int walkExprList(ExprList *p, int (*xFunc)(void *, Expr*), void *pArg){

   int i;

   struct ExprList_item *pItem;

   if( !p ) return 0;

   for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){

     if( walkExprTree(pItem->pExpr, xFunc, pArg) ) return 1;

   }

   return 0;

 }

 /*

 ** Call walkExprTree() for every expression in Select p, not including

 ** expressions that are part of sub-selects in any FROM clause or the LIMIT

 ** or OFFSET expressions..

 */

 static int walkSelectExpr(Select *p, int (*xFunc)(void *, Expr*), void *pArg){

   walkExprList(p->pEList, xFunc, pArg);

   walkExprTree(p->pWhere, xFunc, pArg);

   walkExprList(p->pGroupBy, xFunc, pArg);

   walkExprTree(p->pHaving, xFunc, pArg);

   walkExprList(p->pOrderBy, xFunc, pArg);

   if( p->pPrior ){

     walkSelectExpr(p->pPrior, xFunc, pArg);

   }

   return 0;

 }

 /*

 ** This routine is designed as an xFunc for walkExprTree().

 **

 ** pArg is really a pointer to an integer.  If we can tell by looking

 ** at pExpr that the expression that contains pExpr is not a constant

 ** expression, then set *pArg to 0 and return 2 to abandon the tree walk.

 ** If pExpr does does not disqualify the expression from being a constant

 ** then do nothing.

 **

 ** After walking the whole tree, if no nodes are found that disqualify

 ** the expression as constant, then we assume the whole expression

 ** is constant.  See sqlite3ExprIsConstant() for additional information.

 */

 static int exprNodeIsConstant(void *pArg, Expr *pExpr){

   int *pN = (int*)pArg;

   /* If *pArg is 3 then any term of the expression that comes from

   ** the ON or USING clauses of a join disqualifies the expression

   ** from being considered constant. */

   if( (*pN)==3 && ExprHasAnyProperty(pExpr, EP_FromJoin) ){

     *pN = 0;

     return 2;

   }

   switch( pExpr->op ){

     /* Consider functions to be constant if all their arguments are constant

     ** and *pArg==2 */

     case TK_FUNCTION:

       if( (*pN)==2 ) return 0;

       /* Fall through */

     case TK_ID:

     case TK_COLUMN:

     case TK_DOT:

     case TK_AGG_FUNCTION:

     case TK_AGG_COLUMN:

 #ifndef SQLITE_OMIT_SUBQUERY

     case TK_SELECT:

     case TK_EXISTS:

       testcase( pExpr->op==TK_SELECT );

       testcase( pExpr->op==TK_EXISTS );

 #endif

       testcase( pExpr->op==TK_ID );

       testcase( pExpr->op==TK_COLUMN );

       testcase( pExpr->op==TK_DOT );

       testcase( pExpr->op==TK_AGG_FUNCTION );

       testcase( pExpr->op==TK_AGG_COLUMN );

       *pN = 0;

       return 2;

     case TK_IN:

       if( pExpr->pSelect ){

         *pN = 0;

         return 2;

       }

     default:

       return 0;

   }

 }

 /*

 ** Walk an expression tree.  Return 1 if the expression is constant

 ** and 0 if it involves variables or function calls.

 **

 ** For the purposes of this function, a double-quoted string (ex: "abc")

 ** is considered a variable but a single-quoted string (ex: 'abc') is

 ** a constant.

 */

 int sqlite3ExprIsConstant(Expr *p){

   int isConst = 1;

   walkExprTree(p, exprNodeIsConstant, &isConst);

   return isConst;

 }

 /*

 ** Walk an expression tree.  Return 1 if the expression is constant

 ** that does no originate from the ON or USING clauses of a join.

 ** Return 0 if it involves variables or function calls or terms from

 ** an ON or USING clause.

 */

 int sqlite3ExprIsConstantNotJoin(Expr *p){

   int isConst = 3;

   walkExprTree(p, exprNodeIsConstant, &isConst);

   return isConst!=0;

 }

 /*

 ** Walk an expression tree.  Return 1 if the expression is constant

 ** or a function call with constant arguments.  Return and 0 if there

 ** are any variables.

 **

 ** For the purposes of this function, a double-quoted string (ex: "abc")

 ** is considered a variable but a single-quoted string (ex: 'abc') is

 ** a constant.

 */

 int sqlite3ExprIsConstantOrFunction(Expr *p){

   int isConst = 2;

   walkExprTree(p, exprNodeIsConstant, &isConst);

   return isConst!=0;

 }

 /*

 ** If the expression p codes a constant integer that is small enough

 ** to fit in a 32-bit integer, return 1 and put the value of the integer

 ** in *pValue.  If the expression is not an integer or if it is too big

 ** to fit in a signed 32-bit integer, return 0 and leave *pValue unchanged.

 */

 int sqlite3ExprIsInteger(Expr *p, int *pValue){

   int rc = 0;

   if( p->flags & EP_IntValue ){

     *pValue = p->iTable;

     return 1;

   }

   switch( p->op ){

     case TK_INTEGER: {

       rc = sqlite3GetInt32((char*)p->token.z, pValue);

       break;

     }

     case TK_UPLUS: {

       rc = sqlite3ExprIsInteger(p->pLeft, pValue);

       break;

     }

     case TK_UMINUS: {

       int v;

       if( sqlite3ExprIsInteger(p->pLeft, &v) ){

         *pValue = -v;

         rc = 1;

       }

       break;

     }

     default: break;

   }

   if( rc ){

     p->op = TK_INTEGER;

     p->flags |= EP_IntValue;

     p->iTable = *pValue;

   }

   return rc;

 }

 /*

 ** Return TRUE if the given string is a row-id column name.

 */

 int sqlite3IsRowid(const char *z){

   if( sqlite3StrICmp(z, "_ROWID_")==0 ) return 1;

   if( sqlite3StrICmp(z, "ROWID")==0 ) return 1;

   if( sqlite3StrICmp(z, "OID")==0 ) return 1;

   return 0;

 }

 /*

 ** Given the name of a column of the form X.Y.Z or Y.Z or just Z, look up

 ** that name in the set of source tables in pSrcList and make the pExpr 

 ** expression node refer back to that source column.  The following changes

 ** are made to pExpr:

 **

 **    pExpr->iDb           Set the index in db->aDb[] of the database holding

 **                         the table.

 **    pExpr->iTable        Set to the cursor number for the table obtained

 **                         from pSrcList.

 **    pExpr->iColumn       Set to the column number within the table.

 **    pExpr->op            Set to TK_COLUMN.

 **    pExpr->pLeft         Any expression this points to is deleted

 **    pExpr->pRight        Any expression this points to is deleted.

 **

 ** The pDbToken is the name of the database (the "X").  This value may be

 ** NULL meaning that name is of the form Y.Z or Z.  Any available database

 ** can be used.  The pTableToken is the name of the table (the "Y").  This

 ** value can be NULL if pDbToken is also NULL.  If pTableToken is NULL it

 ** means that the form of the name is Z and that columns from any table

 ** can be used.

 **

 ** If the name cannot be resolved unambiguously, leave an error message

 ** in pParse and return non-zero.  Return zero on success.

 */

 static int lookupName(

   Parse *pParse,       /* The parsing context */

   Token *pDbToken,     /* Name of the database containing table, or NULL */

   Token *pTableToken,  /* Name of table containing column, or NULL */

   Token *pColumnToken, /* Name of the column. */

   NameContext *pNC,    /* The name context used to resolve the name */

   Expr *pExpr          /* Make this EXPR node point to the selected column */

 ){

   char *zDb = 0;       /* Name of the database.  The "X" in X.Y.Z */

   char *zTab = 0;      /* Name of the table.  The "Y" in X.Y.Z or Y.Z */

   char *zCol = 0;      /* Name of the column.  The "Z" */

   int i, j;            /* Loop counters */

   int cnt = 0;         /* Number of matching column names */

   int cntTab = 0;      /* Number of matching table names */

   sqlite3 *db = pParse->db;  /* The database */

   struct SrcList_item *pItem;       /* Use for looping over pSrcList items */

   struct SrcList_item *pMatch = 0;  /* The matching pSrcList item */

   NameContext *pTopNC = pNC;        /* First namecontext in the list */

   Schema *pSchema = 0;              /* Schema of the expression */

   assert( pColumnToken && pColumnToken->z ); /* The Z in X.Y.Z cannot be NULL */

   zDb = sqlite3NameFromToken(db, pDbToken);

   zTab = sqlite3NameFromToken(db, pTableToken);

   zCol = sqlite3NameFromToken(db, pColumnToken);

   if( db->mallocFailed ){

     goto lookupname_end;

   }

   pExpr->iTable = -1;

   while( pNC && cnt==0 ){

     ExprList *pEList;

     SrcList *pSrcList = pNC->pSrcList;

     if( pSrcList ){

       for(i=0, pItem=pSrcList->a; i<pSrcList->nSrc; i++, pItem++){

         Table *pTab;

         int iDb;

         Column *pCol;

         pTab = pItem->pTab;

         assert( pTab!=0 );

         iDb = sqlite3SchemaToIndex(db, pTab->pSchema);

         assert( pTab->nCol>0 );

         if( zTab ){

           if( pItem->zAlias ){

             char *zTabName = pItem->zAlias;

             if( sqlite3StrICmp(zTabName, zTab)!=0 ) continue;

           }else{

             char *zTabName = pTab->zName;

             if( zTabName==0 || sqlite3StrICmp(zTabName, zTab)!=0 ) continue;

             if( zDb!=0 && sqlite3StrICmp(db->aDb[iDb].zName, zDb)!=0 ){

               continue;

             }

           }

         }

         if( 0==(cntTab++) ){

           pExpr->iTable = pItem->iCursor;

           pSchema = pTab->pSchema;

           pMatch = pItem;

         }

         for(j=0, pCol=pTab->aCol; j<pTab->nCol; j++, pCol++){

           if( sqlite3StrICmp(pCol->zName, zCol)==0 ){

             const char *zColl = pTab->aCol[j].zColl;

             IdList *pUsing;

             cnt++;

             pExpr->iTable = pItem->iCursor;

             pMatch = pItem;

             pSchema = pTab->pSchema;

             /* Substitute the rowid (column -1) for the INTEGER PRIMARY KEY */

             pExpr->iColumn = j==pTab->iPKey ? -1 : j;

             pExpr->affinity = pTab->aCol[j].affinity;

             if( (pExpr->flags & EP_ExpCollate)==0 ){

               pExpr->pColl = sqlite3FindCollSeq(db, ENC(db), zColl,-1, 0);

             }

             if( i<pSrcList->nSrc-1 ){

               if( pItem[1].jointype & JT_NATURAL ){

                 /* If this match occurred in the left table of a natural join,

                 ** then skip the right table to avoid a duplicate match */

                 pItem++;

                 i++;

               }else if( (pUsing = pItem[1].pUsing)!=0 ){

                 /* If this match occurs on a column that is in the USING clause

                 ** of a join, skip the search of the right table of the join

                 ** to avoid a duplicate match there. */

                 int k;

                 for(k=0; k<pUsing->nId; k++){

                   if( sqlite3StrICmp(pUsing->a[k].zName, zCol)==0 ){

                     pItem++;

                     i++;

                     break;

                   }

                 }

               }

             }

             break;

           }

         }

       }

     }

 #ifndef SQLITE_OMIT_TRIGGER

     /* If we have not already resolved the name, then maybe 

     ** it is a new.* or old.* trigger argument reference

     */

     if( zDb==0 && zTab!=0 && cnt==0 && pParse->trigStack!=0 ){

       TriggerStack *pTriggerStack = pParse->trigStack;

       Table *pTab = 0;

       u32 *piColMask;

       if( pTriggerStack->newIdx != -1 && sqlite3StrICmp("new", zTab) == 0 ){

         pExpr->iTable = pTriggerStack->newIdx;

         assert( pTriggerStack->pTab );

         pTab = pTriggerStack->pTab;

         piColMask = &(pTriggerStack->newColMask);

       }else if( pTriggerStack->oldIdx != -1 && sqlite3StrICmp("old", zTab)==0 ){

         pExpr->iTable = pTriggerStack->oldIdx;

         assert( pTriggerStack->pTab );

         pTab = pTriggerStack->pTab;

         piColMask = &(pTriggerStack->oldColMask);

       }

       if( pTab ){ 

         int iCol;

         Column *pCol = pTab->aCol;

         pSchema = pTab->pSchema;

         cntTab++;

         for(iCol=0; iCol < pTab->nCol; iCol++, pCol++) {

           if( sqlite3StrICmp(pCol->zName, zCol)==0 ){

             const char *zColl = pTab->aCol[iCol].zColl;

             cnt++;

             pExpr->iColumn = iCol==pTab->iPKey ? -1 : iCol;

             pExpr->affinity = pTab->aCol[iCol].affinity;

             if( (pExpr->flags & EP_ExpCollate)==0 ){

               pExpr->pColl = sqlite3FindCollSeq(db, ENC(db), zColl,-1, 0);

             }

             pExpr->pTab = pTab;

             if( iCol>=0 ){

               testcase( iCol==31 );

               testcase( iCol==32 );

               *piColMask |= ((u32)1<<iCol) | (iCol>=32?0xffffffff:0);

             }

             break;

           }

         }

       }

     }

 #endif /* !defined(SQLITE_OMIT_TRIGGER) */

     /*

     ** Perhaps the name is a reference to the ROWID

     */

     if( cnt==0 && cntTab==1 && sqlite3IsRowid(zCol) ){

       cnt = 1;

       pExpr->iColumn = -1;

       pExpr->affinity = SQLITE_AFF_INTEGER;

     }

     /*

     ** If the input is of the form Z (not Y.Z or X.Y.Z) then the name Z

     ** might refer to an result-set alias.  This happens, for example, when

     ** we are resolving names in the WHERE clause of the following command:

     **

     **     SELECT a+b AS x FROM table WHERE x<10;

     **

     ** In cases like this, replace pExpr with a copy of the expression that

     ** forms the result set entry ("a+b" in the example) and return immediately.

     ** Note that the expression in the result set should have already been

     ** resolved by the time the WHERE clause is resolved.

     */

     if( cnt==0 && (pEList = pNC->pEList)!=0 && zTab==0 ){

       for(j=0; j<pEList->nExpr; j++){

         char *zAs = pEList->a[j].zName;

         if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){

           Expr *pDup, *pOrig;

           assert( pExpr->pLeft==0 && pExpr->pRight==0 );

           assert( pExpr->pList==0 );

           assert( pExpr->pSelect==0 );

           pOrig = pEList->a[j].pExpr;

           if( !pNC->allowAgg && ExprHasProperty(pOrig, EP_Agg) ){

             sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);

             sqlite3DbFree(db, zCol);

             return 2;

           }

           pDup = sqlite3ExprDup(db, pOrig);

           if( pExpr->flags & EP_ExpCollate ){

             pDup->pColl = pExpr->pColl;

             pDup->flags |= EP_ExpCollate;

           }

           if( pExpr->span.dyn ) sqlite3DbFree(db, (char*)pExpr->span.z);

           if( pExpr->token.dyn ) sqlite3DbFree(db, (char*)pExpr->token.z);

           memcpy(pExpr, pDup, sizeof(*pExpr));

           sqlite3DbFree(db, pDup);

           cnt = 1;

           pMatch = 0;

           assert( zTab==0 && zDb==0 );

           goto lookupname_end_2;

         }

       } 

     }

     /* Advance to the next name context.  The loop will exit when either

     ** we have a match (cnt>0) or when we run out of name contexts.

     */

     if( cnt==0 ){

       pNC = pNC->pNext;

     }

   }

   /*

   ** If X and Y are NULL (in other words if only the column name Z is

   ** supplied) and the value of Z is enclosed in double-quotes, then

   ** Z is a string literal if it doesn't match any column names.  In that

   ** case, we need to return right away and not make any changes to

   ** pExpr.

   **

   ** Because no reference was made to outer contexts, the pNC->nRef

   ** fields are not changed in any context.

   */

   if( cnt==0 && zTab==0 && pColumnToken->z[0]=='"' ){

     sqlite3DbFree(db, zCol);

     return 0;

   }

   /*

   ** cnt==0 means there was not match.  cnt>1 means there were two or

   ** more matches.  Either way, we have an error.

   */

   if( cnt!=1 ){

     const char *zErr;

     zErr = cnt==0 ? "no such column" : "ambiguous column name";

     if( zDb ){

       sqlite3ErrorMsg(pParse, "%s: %s.%s.%s", zErr, zDb, zTab, zCol);

     }else if( zTab ){

       sqlite3ErrorMsg(pParse, "%s: %s.%s", zErr, zTab, zCol);

     }else{

       sqlite3ErrorMsg(pParse, "%s: %s", zErr, zCol);

     }

     pTopNC->nErr++;

   }

   /* If a column from a table in pSrcList is referenced, then record

   ** this fact in the pSrcList.a[].colUsed bitmask.  Column 0 causes

   ** bit 0 to be set.  Column 1 sets bit 1.  And so forth.  If the

   ** column number is greater than the number of bits in the bitmask

   ** then set the high-order bit of the bitmask.

   */

   if( pExpr->iColumn>=0 && pMatch!=0 ){

     int n = pExpr->iColumn;

     testcase( n==sizeof(Bitmask)*8-1 );

     if( n>=sizeof(Bitmask)*8 ){

       n = sizeof(Bitmask)*8-1;

     }

     assert( pMatch->iCursor==pExpr->iTable );

     pMatch->colUsed |= ((Bitmask)1)<<n;

   }

 lookupname_end:

   /* Clean up and return

   */

   sqlite3DbFree(db, zDb);

   sqlite3DbFree(db, zTab);

   sqlite3ExprDelete(db, pExpr->pLeft);

   pExpr->pLeft = 0;

   sqlite3ExprDelete(db, pExpr->pRight);

   pExpr->pRight = 0;

   pExpr->op = TK_COLUMN;

 lookupname_end_2:

   sqlite3DbFree(db, zCol);

   if( cnt==1 ){

     assert( pNC!=0 );

     sqlite3AuthRead(pParse, pExpr, pSchema, pNC->pSrcList);

     if( pMatch && !pMatch->pSelect ){

       pExpr->pTab = pMatch->pTab;

     }

     /* Increment the nRef value on all name contexts from TopNC up to

     ** the point where the name matched. */

     for(;;){

       assert( pTopNC!=0 );

       pTopNC->nRef++;

       if( pTopNC==pNC ) break;

       pTopNC = pTopNC->pNext;

     }

     return 0;

   } else {

     return 1;

   }

 }

 /*

 ** This routine is designed as an xFunc for walkExprTree().

 **

 ** Resolve symbolic names into TK_COLUMN operators for the current

 ** node in the expression tree.  Return 0 to continue the search down

 ** the tree or 2 to abort the tree walk.

 **

 ** This routine also does error checking and name resolution for

 ** function names.  The operator for aggregate functions is changed

 ** to TK_AGG_FUNCTION.

 */

 static int nameResolverStep(void *pArg, Expr *pExpr){

   NameContext *pNC = (NameContext*)pArg;

   Parse *pParse;

   if( pExpr==0 ) return 1;

   assert( pNC!=0 );

   pParse = pNC->pParse;

   if( ExprHasAnyProperty(pExpr, EP_Resolved) ) return 1;

   ExprSetProperty(pExpr, EP_Resolved);

 #ifndef NDEBUG

   if( pNC->pSrcList && pNC->pSrcList->nAlloc>0 ){

     SrcList *pSrcList = pNC->pSrcList;

     int i;

     for(i=0; i<pNC->pSrcList->nSrc; i++){

       assert( pSrcList->a[i].iCursor>=0 && pSrcList->a[i].iCursor<pParse->nTab);

     }

   }

 #endif

   switch( pExpr->op ){

     /* Double-quoted strings (ex: "abc") are used as identifiers if

     ** possible.  Otherwise they remain as strings.  Single-quoted

     ** strings (ex: 'abc') are always string literals.

     */

     case TK_STRING: {

       if( pExpr->token.z[0]=='\'' ) break;

       /* Fall thru into the TK_ID case if this is a double-quoted string */

     }

     /* A lone identifier is the name of a column.

     */

     case TK_ID: {

       lookupName(pParse, 0, 0, &pExpr->token, pNC, pExpr);

       return 1;

     }

     /* A table name and column name:     ID.ID

     ** Or a database, table and column:  ID.ID.ID

     */

     case TK_DOT: {

       Token *pColumn;

       Token *pTable;

       Token *pDb;

       Expr *pRight;

       /* if( pSrcList==0 ) break; */

       pRight = pExpr->pRight;

       if( pRight->op==TK_ID ){

         pDb = 0;

         pTable = &pExpr->pLeft->token;

         pColumn = &pRight->token;

       }else{

         assert( pRight->op==TK_DOT );

         pDb = &pExpr->pLeft->token;

         pTable = &pRight->pLeft->token;

         pColumn = &pRight->pRight->token;

       }

       lookupName(pParse, pDb, pTable, pColumn, pNC, pExpr);

       return 1;

     }

     /* Resolve function names

     */

     case TK_CONST_FUNC:

     case TK_FUNCTION: {

       ExprList *pList = pExpr->pList;    /* The argument list */

       int n = pList ? pList->nExpr : 0;  /* Number of arguments */

       int no_such_func = 0;       /* True if no such function exists */

       int wrong_num_args = 0;     /* True if wrong number of arguments */

       int is_agg = 0;             /* True if is an aggregate function */

       int i;

       int auth;                   /* Authorization to use the function */

       int nId;                    /* Number of characters in function name */

       const char *zId;            /* The function name. */

       FuncDef *pDef;              /* Information about the function */

       int enc = ENC(pParse->db);  /* The database encoding */

       zId = (char*)pExpr->token.z;

       nId = pExpr->token.n;

       pDef = sqlite3FindFunction(pParse->db, zId, nId, n, enc, 0);

       if( pDef==0 ){

         pDef = sqlite3FindFunction(pParse->db, zId, nId, -1, enc, 0);

         if( pDef==0 ){

           no_such_func = 1;

         }else{

           wrong_num_args = 1;

         }

       }else{

         is_agg = pDef->xFunc==0;

       }

 #ifndef SQLITE_OMIT_AUTHORIZATION

       if( pDef ){

         auth = sqlite3AuthCheck(pParse, SQLITE_FUNCTION, 0, pDef->zName, 0);

         if( auth!=SQLITE_OK ){

           if( auth==SQLITE_DENY ){

             sqlite3ErrorMsg(pParse, "not authorized to use function: %s",

                                     pDef->zName);

             pNC->nErr++;

           }

           pExpr->op = TK_NULL;

           return 1;

         }

       }

 #endif

       if( is_agg && !pNC->allowAgg ){

         sqlite3ErrorMsg(pParse, "misuse of aggregate function %.*s()", nId,zId);

         pNC->nErr++;

         is_agg = 0;

       }else if( no_such_func ){

         sqlite3ErrorMsg(pParse, "no such function: %.*s", nId, zId);

         pNC->nErr++;

       }else if( wrong_num_args ){

         sqlite3ErrorMsg(pParse,"wrong number of arguments to function %.*s()",

              nId, zId);

         pNC->nErr++;

       }

       if( is_agg ){

         pExpr->op = TK_AGG_FUNCTION;

         pNC->hasAgg = 1;

       }

       if( is_agg ) pNC->allowAgg = 0;

       for(i=0; pNC->nErr==0 && i<n; i++){

         walkExprTree(pList->a[i].pExpr, nameResolverStep, pNC);

       }

       if( is_agg ) pNC->allowAgg = 1;

       /* FIX ME:  Compute pExpr->affinity based on the expected return

       ** type of the function 

       */

       return is_agg;

     }

 #ifndef SQLITE_OMIT_SUBQUERY

     case TK_SELECT:

     case TK_EXISTS:

 #endif

     case TK_IN: {

       if( pExpr->pSelect ){

         int nRef = pNC->nRef;

 #ifndef SQLITE_OMIT_CHECK

         if( pNC->isCheck ){

           sqlite3ErrorMsg(pParse,"subqueries prohibited in CHECK constraints");

         }

 #endif

         sqlite3SelectResolve(pParse, pExpr->pSelect, pNC);

         assert( pNC->nRef>=nRef );

         if( nRef!=pNC->nRef ){

           ExprSetProperty(pExpr, EP_VarSelect);

         }

       }

       break;

     }

 #ifndef SQLITE_OMIT_CHECK

     case TK_VARIABLE: {

       if( pNC->isCheck ){

         sqlite3ErrorMsg(pParse,"parameters prohibited in CHECK constraints");

       }

       break;

     }

 #endif

   }

   return 0;

 }

 /*

 ** This routine walks an expression tree and resolves references to

 ** table columns.  Nodes of the form ID.ID or ID resolve into an

 ** index to the table in the table list and a column offset.  The 

 ** Expr.opcode for such nodes is changed to TK_COLUMN.  The Expr.iTable

 ** value is changed to the index of the referenced table in pTabList

 ** plus the "base" value.  The base value will ultimately become the

 ** VDBE cursor number for a cursor that is pointing into the referenced

 ** table.  The Expr.iColumn value is changed to the index of the column 

 ** of the referenced table.  The Expr.iColumn value for the special

 ** ROWID column is -1.  Any INTEGER PRIMARY KEY column is tried as an

 ** alias for ROWID.

 **

 ** Also resolve function names and check the functions for proper

 ** usage.  Make sure all function names are recognized and all functions

 ** have the correct number of arguments.  Leave an error message

 ** in pParse->zErrMsg if anything is amiss.  Return the number of errors.

 **

 ** If the expression contains aggregate functions then set the EP_Agg

 ** property on the expression.

 */

 int sqlite3ExprResolveNames( 

   NameContext *pNC,       /* Namespace to resolve expressions in. */

   Expr *pExpr             /* The expression to be analyzed. */

 ){

   int savedHasAgg;

   if( pExpr==0 ) return 0;

 #if SQLITE_MAX_EXPR_DEPTH>0

   {

     if( checkExprHeight(pNC->pParse, pExpr->nHeight + pNC->pParse->nHeight) ){

       return 1;

     }

     pNC->pParse->nHeight += pExpr->nHeight;

   }

 #endif

   savedHasAgg = pNC->hasAgg;

   pNC->hasAgg = 0;

   walkExprTree(pExpr, nameResolverStep, pNC);

 #if SQLITE_MAX_EXPR_DEPTH>0

   pNC->pParse->nHeight -= pExpr->nHeight;

 #endif

   if( pNC->nErr>0 ){

     ExprSetProperty(pExpr, EP_Error);

   }

   if( pNC->hasAgg ){

     ExprSetProperty(pExpr, EP_Agg);

   }else if( savedHasAgg ){

     pNC->hasAgg = 1;

   }

   return ExprHasProperty(pExpr, EP_Error);

 }

 /*

 ** A pointer instance of this structure is used to pass information

 ** through walkExprTree into codeSubqueryStep().

 */

 typedef struct QueryCoder QueryCoder;

 struct QueryCoder {

   Parse *pParse;       /* The parsing context */

   NameContext *pNC;    /* Namespace of first enclosing query */

 };

 #ifdef SQLITE_TEST

   int sqlite3_enable_in_opt = 1;

 #else

   #define sqlite3_enable_in_opt 1

 #endif

 /*

 ** Return true if the IN operator optimization is enabled and

 ** the SELECT statement p exists and is of the

 ** simple form:

 **

 **     SELECT <column> FROM <table>

 **

 ** If this is the case, it may be possible to use an existing table

 ** or index instead of generating an epheremal table.

 */

 #ifndef SQLITE_OMIT_SUBQUERY

 static int isCandidateForInOpt(Select *p){

   SrcList *pSrc;

   ExprList *pEList;

   Table *pTab;

   if( !sqlite3_enable_in_opt ) return 0; /* IN optimization must be enabled */

   if( p==0 ) return 0;                   /* right-hand side of IN is SELECT */

   if( p->pPrior ) return 0;              /* Not a compound SELECT */

   if( p->isDistinct ) return 0;          /* No DISTINCT keyword */

   if( p->isAgg ) return 0;               /* Contains no aggregate functions */

   if( p->pGroupBy ) return 0;            /* Has no GROUP BY clause */

   if( p->pLimit ) return 0;              /* Has no LIMIT clause */

   if( p->pOffset ) return 0;

   if( p->pWhere ) return 0;              /* Has no WHERE clause */

   pSrc = p->pSrc;

   if( pSrc==0 ) return 0;                /* A single table in the FROM clause */

   if( pSrc->nSrc!=1 ) return 0;

   if( pSrc->a[0].pSelect ) return 0;     /* FROM clause is not a subquery */

   pTab = pSrc->a[0].pTab;

   if( pTab==0 ) return 0;

   if( pTab->pSelect ) return 0;          /* FROM clause is not a view */

   if( IsVirtual(pTab) ) return 0;        /* FROM clause not a virtual table */

   pEList = p->pEList;

   if( pEList->nExpr!=1 ) return 0;       /* One column in the result set */

   if( pEList->a[0].pExpr->op!=TK_COLUMN ) return 0; /* Result is a column */

   return 1;

 }

 #endif /* SQLITE_OMIT_SUBQUERY */

 /*

 ** This function is used by the implementation of the IN (...) operator.

 ** It's job is to find or create a b-tree structure that may be used

 ** either to test for membership of the (...) set or to iterate through

 ** its members, skipping duplicates.

 **

 ** The cursor opened on the structure (database table, database index 

 ** or ephermal table) is stored in pX->iTable before this function returns.

 ** The returned value indicates the structure type, as follows:

 **

 **   IN_INDEX_ROWID - The cursor was opened on a database table.

 **   IN_INDEX_INDEX - The cursor was opened on a database index.

 **   IN_INDEX_EPH -   The cursor was opened on a specially created and

 **                    populated epheremal table.

 **

 ** An existing structure may only be used if the SELECT is of the simple

 ** form:

 **

 **     SELECT <column> FROM <table>

 **

 ** If prNotFound parameter is 0, then the structure will be used to iterate

 ** through the set members, skipping any duplicates. In this case an

 ** epheremal table must be used unless the selected <column> is guaranteed

 ** to be unique - either because it is an INTEGER PRIMARY KEY or it

 ** is unique by virtue of a constraint or implicit index.

 **

 ** If the prNotFound parameter is not 0, then the structure will be used 

 ** for fast set membership tests. In this case an epheremal table must 

 ** be used unless <column> is an INTEGER PRIMARY KEY or an index can 

 ** be found with <column> as its left-most column.

 **

 ** When the structure is being used for set membership tests, the user

 ** needs to know whether or not the structure contains an SQL NULL 

 ** value in order to correctly evaluate expressions like "X IN (Y, Z)".

 ** If there is a chance that the structure may contain a NULL value at

 ** runtime, then a register is allocated and the register number written

 ** to *prNotFound. If there is no chance that the structure contains a

 ** NULL value, then *prNotFound is left unchanged.

 **

 ** If a register is allocated and its location stored in *prNotFound, then

 ** its initial value is NULL. If the structure does not remain constant

 ** for the duration of the query (i.e. the set is a correlated sub-select), 

 ** the value of the allocated register is reset to NULL each time the 

 ** structure is repopulated. This allows the caller to use vdbe code 

 ** equivalent to the following:

 **

 **   if( register==NULL ){

 **     has_null = <test if data structure contains null>

 **     register = 1

 **   }

 **

 ** in order to avoid running the <test if data structure contains null>

 ** test more often than is necessary.

 */

 #ifndef SQLITE_OMIT_SUBQUERY

 int sqlite3FindInIndex(Parse *pParse, Expr *pX, int *prNotFound){

   Select *p;

   int eType = 0;

   int iTab = pParse->nTab++;

   int mustBeUnique = !prNotFound;

   /* The follwing if(...) expression is true if the SELECT is of the 

   ** simple form:

   **

   **     SELECT <column> FROM <table>

   **

   ** If this is the case, it may be possible to use an existing table

   ** or index instead of generating an epheremal table.

   */

   p = pX->pSelect;

   if( isCandidateForInOpt(p) ){

     sqlite3 *db = pParse->db;

     Index *pIdx;

     Expr *pExpr = p->pEList->a[0].pExpr;

     int iCol = pExpr->iColumn;

     Vdbe *v = sqlite3GetVdbe(pParse);

     /* This function is only called from two places. In both cases the vdbe

     ** has already been allocated. So assume sqlite3GetVdbe() is always

     ** successful here.

     */

     assert(v);

     if( iCol<0 ){

       int iMem = ++pParse->nMem;

       int iAddr;

       Table *pTab = p->pSrc->a[0].pTab;

       int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);

       sqlite3VdbeUsesBtree(v, iDb);

       iAddr = sqlite3VdbeAddOp1(v, OP_If, iMem);

       sqlite3VdbeAddOp2(v, OP_Integer, 1, iMem);

       sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);

       eType = IN_INDEX_ROWID;

       sqlite3VdbeJumpHere(v, iAddr);

     }else{

       /* The collation sequence used by the comparison. If an index is to 

       ** be used in place of a temp-table, it must be ordered according

       ** to this collation sequence.

       */

       CollSeq *pReq = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pExpr);

       /* Check that the affinity that will be used to perform the 

       ** comparison is the same as the affinity of the column. If

       ** it is not, it is not possible to use any index.

       */

       Table *pTab = p->pSrc->a[0].pTab;

       char aff = comparisonAffinity(pX);

       int affinity_ok = (pTab->aCol[iCol].affinity==aff||aff==SQLITE_AFF_NONE);

       for(pIdx=pTab->pIndex; pIdx && eType==0 && affinity_ok; pIdx=pIdx->pNext){

         if( (pIdx->aiColumn[0]==iCol)

          && (pReq==sqlite3FindCollSeq(db, ENC(db), pIdx->azColl[0], -1, 0))

          && (!mustBeUnique || (pIdx->nColumn==1 && pIdx->onError!=OE_None))

         ){

           int iDb;

           int iMem = ++pParse->nMem;

           int iAddr;

           char *pKey;

           pKey = (char *)sqlite3IndexKeyinfo(pParse, pIdx);

           iDb = sqlite3SchemaToIndex(db, pIdx->pSchema);

           sqlite3VdbeUsesBtree(v, iDb);

           iAddr = sqlite3VdbeAddOp1(v, OP_If, iMem);

           sqlite3VdbeAddOp2(v, OP_Integer, 1, iMem);

           sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pIdx->nColumn);

           sqlite3VdbeAddOp4(v, OP_OpenRead, iTab, pIdx->tnum, iDb,

                                pKey,P4_KEYINFO_HANDOFF);

           VdbeComment((v, "%s", pIdx->zName));

           eType = IN_INDEX_INDEX;

           sqlite3VdbeJumpHere(v, iAddr);

           if( prNotFound && !pTab->aCol[iCol].notNull ){

             *prNotFound = ++pParse->nMem;

           }

         }

       }

     }

   }

   if( eType==0 ){

     int rMayHaveNull = 0;

     if( prNotFound ){

       *prNotFound = rMayHaveNull = ++pParse->nMem;

     }

     sqlite3CodeSubselect(pParse, pX, rMayHaveNull);

     eType = IN_INDEX_EPH;

   }else{

     pX->iTable = iTab;

   }

   return eType;

 }

 #endif

 /*

 ** Generate code for scalar subqueries used as an expression

 ** and IN operators.  Examples:

 **

 **     (SELECT a FROM b)          -- subquery

 **     EXISTS (SELECT a FROM b)   -- EXISTS subquery

 **     x IN (4,5,11)              -- IN operator with list on right-hand side

 **     x IN (SELECT a FROM b)     -- IN operator with subquery on the right

 **

 ** The pExpr parameter describes the expression that contains the IN

 ** operator or subquery.

 */

 #ifndef SQLITE_OMIT_SUBQUERY

 void sqlite3CodeSubselect(Parse *pParse, Expr *pExpr, int rMayHaveNull){

   int testAddr = 0;                       /* One-time test address */

   Vdbe *v = sqlite3GetVdbe(pParse);

   if( v==0 ) return;

   /* This code must be run in its entirety every time it is encountered

   ** if any of the following is true:

   **

   **    *  The right-hand side is a correlated subquery

   **    *  The right-hand side is an expression list containing variables

   **    *  We are inside a trigger

   **

   ** If all of the above are false, then we can run this code just once

   ** save the results, and reuse the same result on subsequent invocations.

   */

   if( !ExprHasAnyProperty(pExpr, EP_VarSelect) && !pParse->trigStack ){

     int mem = ++pParse->nMem;

     sqlite3VdbeAddOp1(v, OP_If, mem);

     testAddr = sqlite3VdbeAddOp2(v, OP_Integer, 1, mem);

     assert( testAddr>0 || pParse->db->mallocFailed );

   }

   switch( pExpr->op ){

     case TK_IN: {

       char affinity;

       KeyInfo keyInfo;

       int addr;        /* Address of OP_OpenEphemeral instruction */

       if( rMayHaveNull ){

         sqlite3VdbeAddOp2(v, OP_Null, 0, rMayHaveNull);

       }

       affinity = sqlite3ExprAffinity(pExpr->pLeft);

       /* Whether this is an 'x IN(SELECT...)' or an 'x IN(<exprlist>)'

       ** expression it is handled the same way. A virtual table is 

       ** filled with single-field index keys representing the results

       ** from the SELECT or the <exprlist>.

       **

       ** If the 'x' expression is a column value, or the SELECT...

       ** statement returns a column value, then the affinity of that

       ** column is used to build the index keys. If both 'x' and the

       ** SELECT... statement are columns, then numeric affinity is used

       ** if either column has NUMERIC or INTEGER affinity. If neither

       ** 'x' nor the SELECT... statement are columns, then numeric affinity

       ** is used.

       */

       pExpr->iTable = pParse->nTab++;

       addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pExpr->iTable, 1);

       memset(&keyInfo, 0, sizeof(keyInfo));

       keyInfo.nField = 1;

       if( pExpr->pSelect ){

         /* Case 1:     expr IN (SELECT ...)

         **

         ** Generate code to write the results of the select into the temporary

         ** table allocated and opened above.

         */

         SelectDest dest;

         ExprList *pEList;

         sqlite3SelectDestInit(&dest, SRT_Set, pExpr->iTable);

         dest.affinity = (int)affinity;

         assert( (pExpr->iTable&0x0000FFFF)==pExpr->iTable );

         if( sqlite3Select(pParse, pExpr->pSelect, &dest, 0, 0, 0) ){

           return;

         }

         pEList = pExpr->pSelect->pEList;

         if( pEList && pEList->nExpr>0 ){ 

           keyInfo.aColl[0] = sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft,

               pEList->a[0].pExpr);

         }

       }else if( pExpr->pList ){

         /* Case 2:     expr IN (exprlist)

         **

         ** For each expression, build an index key from the evaluation and

         ** store it in the temporary table. If <expr> is a column, then use

         ** that columns affinity when building index keys. If <expr> is not

         ** a column, use numeric affinity.

         */

         int i;

         ExprList *pList = pExpr->pList;

         struct ExprList_item *pItem;

         int r1, r2, r3;

         if( !affinity ){

           affinity = SQLITE_AFF_NONE;

         }

         keyInfo.aColl[0] = pExpr->pLeft->pColl;

         /* Loop through each expression in <exprlist>. */

         r1 = sqlite3GetTempReg(pParse);

         r2 = sqlite3GetTempReg(pParse);

         for(i=pList->nExpr, pItem=pList->a; i>0; i--, pItem++){

           Expr *pE2 = pItem->pExpr;

           /* If the expression is not constant then we will need to

           ** disable the test that was generated above that makes sure

           ** this code only executes once.  Because for a non-constant

           ** expression we need to rerun this code each time.

           */

           if( testAddr && !sqlite3ExprIsConstant(pE2) ){

             sqlite3VdbeChangeToNoop(v, testAddr-1, 2);

             testAddr = 0;

           }

           /* Evaluate the expression and insert it into the temp table */

           pParse->disableColCache++;

           r3 = sqlite3ExprCodeTarget(pParse, pE2, r1);

           assert( pParse->disableColCache>0 );

           pParse->disableColCache--;

           sqlite3VdbeAddOp4(v, OP_MakeRecord, r3, 1, r2, &affinity, 1);

           sqlite3ExprCacheAffinityChange(pParse, r3, 1);

           sqlite3VdbeAddOp2(v, OP_IdxInsert, pExpr->iTable, r2);

         }

         sqlite3ReleaseTempReg(pParse, r1);

         sqlite3ReleaseTempReg(pParse, r2);

       }

       sqlite3VdbeChangeP4(v, addr, (void *)&keyInfo, P4_KEYINFO);

       break;

     }

     case TK_EXISTS:

     case TK_SELECT: {

       /* This has to be a scalar SELECT.  Generate code to put the

       ** value of this select in a memory cell and record the number

       ** of the memory cell in iColumn.

       */

       static const Token one = { (u8*)"1", 0, 1 };

       Select *pSel;

       SelectDest dest;

       pSel = pExpr->pSelect;

       sqlite3SelectDestInit(&dest, 0, ++pParse->nMem);

       if( pExpr->op==TK_SELECT ){

         dest.eDest = SRT_Mem;

         sqlite3VdbeAddOp2(v, OP_Null, 0, dest.iParm);

         VdbeComment((v, "Init subquery result"));

       }else{

         dest.eDest = SRT_Exists;

         sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iParm);

         VdbeComment((v, "Init EXISTS result"));

       }

       sqlite3ExprDelete(pParse->db, pSel->pLimit);

       pSel->pLimit = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &one);

       if( sqlite3Select(pParse, pSel, &dest, 0, 0, 0) ){

         return;

       }

       pExpr->iColumn = dest.iParm;

       break;

     }

   }

   if( testAddr ){

     sqlite3VdbeJumpHere(v, testAddr-1);

   }

   return;

 }

 #endif /* SQLITE_OMIT_SUBQUERY */

 /*

 ** Duplicate an 8-byte value

 */

 static char *dup8bytes(Vdbe *v, const char *in){

   char *out = sqlite3DbMallocRaw(sqlite3VdbeDb(v), 8);

   if( out ){

     memcpy(out, in, 8);

   }

   return out;

 }

 /*

 ** Generate an instruction that will put the floating point

 ** value described by z[0..n-1] into register iMem.

 **

 ** The z[] string will probably not be zero-terminated.  But the 

 ** z[n] character is guaranteed to be something that does not look

 ** like the continuation of the number.

 */

 static void codeReal(Vdbe *v, const char *z, int n, int negateFlag, int iMem){

   assert( z || v==0 || sqlite3VdbeDb(v)->mallocFailed );

   if( z ){

     double value;

     char *zV;

     assert( !isdigit(z[n]) );

     sqlite3AtoF(z, &value);

     if( sqlite3IsNaN(value) ){

       sqlite3VdbeAddOp2(v, OP_Null, 0, iMem);

     }else{

       if( negateFlag ) value = -value;

       zV = dup8bytes(v, (char*)&value);

       sqlite3VdbeAddOp4(v, OP_Real, 0, iMem, 0, zV, P4_REAL);

     }

   }

 }

 /*

 ** Generate an instruction that will put the integer describe by

 ** text z[0..n-1] into register iMem.

 **

 ** The z[] string will probably not be zero-terminated.  But the 

 ** z[n] character is guaranteed to be something that does not look

 ** like the continuation of the number.

 */

 static void codeInteger(Vdbe *v, Expr *pExpr, int negFlag, int iMem){

   const char *z;

   if( pExpr->flags & EP_IntValue ){

     int i = pExpr->iTable;

     if( negFlag ) i = -i;

     sqlite3VdbeAddOp2(v, OP_Integer, i, iMem);

   }else if( (z = (char*)pExpr->token.z)!=0 ){

     int i;

     int n = pExpr->token.n;

     assert( !isdigit(z[n]) );

     if( sqlite3GetInt32(z, &i) ){

       if( negFlag ) i = -i;

       sqlite3VdbeAddOp2(v, OP_Integer, i, iMem);

     }else if( sqlite3FitsIn64Bits(z, negFlag) ){

       i64 value;

       char *zV;

       sqlite3Atoi64(z, &value);

       if( negFlag ) value = -value;

       zV = dup8bytes(v, (char*)&value);

       sqlite3VdbeAddOp4(v, OP_Int64, 0, iMem, 0, zV, P4_INT64);

     }else{

       codeReal(v, z, n, negFlag, iMem);

     }

   }

 }

 /*

 ** Generate code that will extract the iColumn-th column from

 ** table pTab and store the column value in a register.  An effort

 ** is made to store the column value in register iReg, but this is

 ** not guaranteed.  The location of the column value is returned.

 **

 ** There must be an open cursor to pTab in iTable when this routine

 ** is called.  If iColumn<0 then code is generated that extracts the rowid.

 **

 ** This routine might attempt to reuse the value of the column that

 ** has already been loaded into a register.  The value will always

 ** be used if it has not undergone any affinity changes.  But if

 ** an affinity change has occurred, then the cached value will only be

 ** used if allowAffChng is true.

 */

 int sqlite3ExprCodeGetColumn(

   Parse *pParse,   /* Parsing and code generating context */

   Table *pTab,     /* Description of the table we are reading from */

   int iColumn,     /* Index of the table column */

   int iTable,      /* The cursor pointing to the table */

   int iReg,        /* Store results here */

   int allowAffChng /* True if prior affinity changes are OK */

 ){

   Vdbe *v = pParse->pVdbe;

   int i;

   struct yColCache *p;

   for(i=0, p=pParse->aColCache; i<pParse->nColCache; i++, p++){

     if( p->iTable==iTable && p->iColumn==iColumn

            && (!p->affChange || allowAffChng) ){

 #if 0

       sqlite3VdbeAddOp0(v, OP_Noop);

       VdbeComment((v, "OPT: tab%d.col%d -> r%d", iTable, iColumn, p->iReg));

 #endif

       return p->iReg;

     }

   }  

   assert( v!=0 );

   if( iColumn<0 ){

     int op = (pTab && IsVirtual(pTab)) ? OP_VRowid : OP_Rowid;

     sqlite3VdbeAddOp2(v, op, iTable, iReg);

   }else if( pTab==0 ){

     sqlite3VdbeAddOp3(v, OP_Column, iTable, iColumn, iReg);

   }else{

     int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;

     sqlite3VdbeAddOp3(v, op, iTable, iColumn, iReg);

     sqlite3ColumnDefault(v, pTab, iColumn);

 #ifndef SQLITE_OMIT_FLOATING_POINT

     if( pTab->aCol[iColumn].affinity==SQLITE_AFF_REAL ){

       sqlite3VdbeAddOp1(v, OP_RealAffinity, iReg);

     }

 #endif

   }

   if( pParse->disableColCache==0 ){

     i = pParse->iColCache;

     p = &pParse->aColCache[i];

     p->iTable = iTable;

     p->iColumn = iColumn;

     p->iReg = iReg;

     p->affChange = 0;

     i++;

     if( i>=ArraySize(pParse->aColCache) ) i = 0;

     if( i>pParse->nColCache ) pParse->nColCache = i;

     pParse->iColCache = i;

   }

   return iReg;

 }

 /*

 ** Clear all column cache entries associated with the vdbe

 ** cursor with cursor number iTable.

 */

 void sqlite3ExprClearColumnCache(Parse *pParse, int iTable){

   if( iTable<0 ){

     pParse->nColCache = 0;

     pParse->iColCache = 0;

   }else{

     int i;

     for(i=0; i<pParse->nColCache; i++){

       if( pParse->aColCache[i].iTable==iTable ){

         testcase( i==pParse->nColCache-1 );

         pParse->aColCache[i] = pParse->aColCache[--pParse->nColCache];

         pParse->iColCache = pParse->nColCache;

       }

     }

   }

 }

 /*

 ** Record the fact that an affinity change has occurred on iCount

 ** registers starting with iStart.

 */

 void sqlite3ExprCacheAffinityChange(Parse *pParse, int iStart, int iCount){

   int iEnd = iStart + iCount - 1;

   int i;

   for(i=0; i<pParse->nColCache; i++){

     int r = pParse->aColCache[i].iReg;

     if( r>=iStart && r<=iEnd ){

       pParse->aColCache[i].affChange = 1;

     }

   }

 }

 /*

 ** Generate code to move content from registers iFrom...iFrom+nReg-1

 ** over to iTo..iTo+nReg-1. Keep the column cache up-to-date.

 */

 void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){

   int i;

   if( iFrom==iTo ) return;

   sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);

   for(i=0; i<pParse->nColCache; i++){

     int x = pParse->aColCache[i].iReg;

     if( x>=iFrom && x<iFrom+nReg ){

       pParse->aColCache[i].iReg += iTo-iFrom;

     }

   }

 }

 /*

 ** Generate code to copy content from registers iFrom...iFrom+nReg-1

 ** over to iTo..iTo+nReg-1.

 */

 void sqlite3ExprCodeCopy(Parse *pParse, int iFrom, int iTo, int nReg){

   int i;

   if( iFrom==iTo ) return;

   for(i=0; i<nReg; i++){

     sqlite3VdbeAddOp2(pParse->pVdbe, OP_Copy, iFrom+i, iTo+i);

   }

 }

 /*

 ** Return true if any register in the range iFrom..iTo (inclusive)

 ** is used as part of the column cache.

 */

 static int usedAsColumnCache(Parse *pParse, int iFrom, int iTo){

   int i;

   for(i=0; i<pParse->nColCache; i++){

     int r = pParse->aColCache[i].iReg;

     if( r>=iFrom && r<=iTo ) return 1;

   }

   return 0;

 }

 /*

 ** Theres is a value in register iCurrent.  We ultimately want

 ** the value to be in register iTarget.  It might be that

 ** iCurrent and iTarget are the same register.

 **

 ** We are going to modify the value, so we need to make sure it

 ** is not a cached register.  If iCurrent is a cached register,

 ** then try to move the value over to iTarget.  If iTarget is a

 ** cached register, then clear the corresponding cache line.

 **

 ** Return the register that the value ends up in.

 */

 int sqlite3ExprWritableRegister(Parse *pParse, int iCurrent, int iTarget){

   int i;

   assert( pParse->pVdbe!=0 );

   if( !usedAsColumnCache(pParse, iCurrent, iCurrent) ){

     return iCurrent;

   }

   if( iCurrent!=iTarget ){

     sqlite3VdbeAddOp2(pParse->pVdbe, OP_SCopy, iCurrent, iTarget);

   }

   for(i=0; i<pParse->nColCache; i++){

     if( pParse->aColCache[i].iReg==iTarget ){

       pParse->aColCache[i] = pParse->aColCache[--pParse->nColCache];

       pParse->iColCache = pParse->nColCache;

     }

   }

   return iTarget;

 }

 /*

 ** If the last instruction coded is an ephemeral copy of any of

 ** the registers in the nReg registers beginning with iReg, then

 ** convert the last instruction from OP_SCopy to OP_Copy.

 */

 void sqlite3ExprHardCopy(Parse *pParse, int iReg, int nReg){

   int addr;

   VdbeOp *pOp;

   Vdbe *v;

   v = pParse->pVdbe;

   addr = sqlite3VdbeCurrentAddr(v);

   pOp = sqlite3VdbeGetOp(v, addr-1);

   assert( pOp || pParse->db->mallocFailed );

   if( pOp && pOp->opcode==OP_SCopy && pOp->p1>=iReg && pOp->p1<iReg+nReg ){

     pOp->opcode = OP_Copy;

   }

 }

 /*

 ** Generate code into the current Vdbe to evaluate the given

 ** expression.  Attempt to store the results in register "target".

 ** Return the register where results are stored.

 **

 ** With this routine, there is no guaranteed that results will

 ** be stored in target.  The result might be stored in some other

 ** register if it is convenient to do so.  The calling function

 ** must check the return code and move the results to the desired

 ** register.

 */

 int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){

   Vdbe *v = pParse->pVdbe;  /* The VM under construction */

   int op;                   /* The opcode being coded */

   int inReg = target;       /* Results stored in register inReg */

   int regFree1 = 0;         /* If non-zero free this temporary register */

   int regFree2 = 0;         /* If non-zero free this temporary register */

   int r1, r2, r3, r4;       /* Various register numbers */

   assert( v!=0 || pParse->db->mallocFailed );

   assert( target>0 && target<=pParse->nMem );

   if( v==0 ) return 0;

   if( pExpr==0 ){

     op = TK_NULL;

   }else{

     op = pExpr->op;

   }

   switch( op ){

     case TK_AGG_COLUMN: {

       AggInfo *pAggInfo = pExpr->pAggInfo;

       struct AggInfo_col *pCol = &pAggInfo->aCol[pExpr->iAgg];

       if( !pAggInfo->directMode ){

         assert( pCol->iMem>0 );

         inReg = pCol->iMem;

         break;

       }else if( pAggInfo->useSortingIdx ){

         sqlite3VdbeAddOp3(v, OP_Column, pAggInfo->sortingIdx,

                               pCol->iSorterColumn, target);

         break;

       }

       /* Otherwise, fall thru into the TK_COLUMN case */

     }

     case TK_COLUMN: {

       if( pExpr->iTable<0 ){

         /* This only happens when coding check constraints */

         assert( pParse->ckBase>0 );

         inReg = pExpr->iColumn + pParse->ckBase;

       }else{

         testcase( (pExpr->flags & EP_AnyAff)!=0 );

         inReg = sqlite3ExprCodeGetColumn(pParse, pExpr->pTab,

                                  pExpr->iColumn, pExpr->iTable, target,

                                  pExpr->flags & EP_AnyAff);

       }

       break;

     }

     case TK_INTEGER: {

       codeInteger(v, pExpr, 0, target);

       break;

     }

     case TK_FLOAT: {

       codeReal(v, (char*)pExpr->token.z, pExpr->token.n, 0, target);

       break;

     }

     case TK_STRING: {

       sqlite3DequoteExpr(pParse->db, pExpr);

       sqlite3VdbeAddOp4(v,OP_String8, 0, target, 0,

                         (char*)pExpr->token.z, pExpr->token.n);

       break;

     }

     case TK_NULL: {

       sqlite3VdbeAddOp2(v, OP_Null, 0, target);

       break;

     }

 #ifndef SQLITE_OMIT_BLOB_LITERAL

     case TK_BLOB: {

       int n;

       const char *z;

       char *zBlob;

       assert( pExpr->token.n>=3 );

       assert( pExpr->token.z[0]=='x' || pExpr->token.z[0]=='X' );

       assert( pExpr->token.z[1]=='\'' );

       assert( pExpr->token.z[pExpr->token.n-1]=='\'' );

       n = pExpr->token.n - 3;

       z = (char*)pExpr->token.z + 2;

       zBlob = sqlite3HexToBlob(sqlite3VdbeDb(v), z, n);

       sqlite3VdbeAddOp4(v, OP_Blob, n/2, target, 0, zBlob, P4_DYNAMIC);

       break;

     }

 #endif

     case TK_VARIABLE: {

       sqlite3VdbeAddOp2(v, OP_Variable, pExpr->iTable, target);

       if( pExpr->token.n>1 ){

         sqlite3VdbeChangeP4(v, -1, (char*)pExpr->token.z, pExpr->token.n);

       }

       break;

     }

     case TK_REGISTER: {

       inReg = pExpr->iTable;

       break;

     }

 #ifndef SQLITE_OMIT_CAST

     case TK_CAST: {

       /* Expressions of the form:   CAST(pLeft AS token) */

       int aff, to_op;

       inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);

       aff = sqlite3AffinityType(&pExpr->token);

       to_op = aff - SQLITE_AFF_TEXT + OP_ToText;

       assert( to_op==OP_ToText    || aff!=SQLITE_AFF_TEXT    );

       assert( to_op==OP_ToBlob    || aff!=SQLITE_AFF_NONE    );

       assert( to_op==OP_ToNumeric || aff!=SQLITE_AFF_NUMERIC );

       assert( to_op==OP_ToInt     || aff!=SQLITE_AFF_INTEGER );

       assert( to_op==OP_ToReal    || aff!=SQLITE_AFF_REAL    );

       testcase( to_op==OP_ToText );

       testcase( to_op==OP_ToBlob );

       testcase( to_op==OP_ToNumeric );

       testcase( to_op==OP_ToInt );

       testcase( to_op==OP_ToReal );

       sqlite3VdbeAddOp1(v, to_op, inReg);

       testcase( usedAsColumnCache(pParse, inReg, inReg) );

       sqlite3ExprCacheAffinityChange(pParse, inReg, 1);

       break;

     }

 #endif /* SQLITE_OMIT_CAST */

     case TK_LT:

     case TK_LE:

     case TK_GT:

     case TK_GE:

     case TK_NE:

     case TK_EQ: {

       assert( TK_LT==OP_Lt );

       assert( TK_LE==OP_Le );

       assert( TK_GT==OP_Gt );

       assert( TK_GE==OP_Ge );

       assert( TK_EQ==OP_Eq );

       assert( TK_NE==OP_Ne );

       testcase( op==TK_LT );

       testcase( op==TK_LE );

       testcase( op==TK_GT );

       testcase( op==TK_GE );

       testcase( op==TK_EQ );

       testcase( op==TK_NE );

       codeCompareOperands(pParse, pExpr->pLeft, &r1, &regFree1,

                                   pExpr->pRight, &r2, &regFree2);

       codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,

                   r1, r2, inReg, SQLITE_STOREP2);

       testcase( regFree1==0 );

       testcase( regFree2==0 );

       break;

     }

     case TK_AND:

     case TK_OR:

     case TK_PLUS:

     case TK_STAR:

     case TK_MINUS:

     case TK_REM:

     case TK_BITAND:

     case TK_BITOR:

     case TK_SLASH:

     case TK_LSHIFT:

     case TK_RSHIFT: 

     case TK_CONCAT: {

       assert( TK_AND==OP_And );

       assert( TK_OR==OP_Or );

       assert( TK_PLUS==OP_Add );

       assert( TK_MINUS==OP_Subtract );

       assert( TK_REM==OP_Remainder );

       assert( TK_BITAND==OP_BitAnd );

       assert( TK_BITOR==OP_BitOr );

       assert( TK_SLASH==OP_Divide );

       assert( TK_LSHIFT==OP_ShiftLeft );

       assert( TK_RSHIFT==OP_ShiftRight );

       assert( TK_CONCAT==OP_Concat );

       testcase( op==TK_AND );

       testcase( op==TK_OR );

       testcase( op==TK_PLUS );

       testcase( op==TK_MINUS );

       testcase( op==TK_REM );

       testcase( op==TK_BITAND );

       testcase( op==TK_BITOR );

       testcase( op==TK_SLASH );

       testcase( op==TK_LSHIFT );

       testcase( op==TK_RSHIFT );

       testcase( op==TK_CONCAT );

       r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);

       r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);

       sqlite3VdbeAddOp3(v, op, r2, r1, target);

       testcase( regFree1==0 );

       testcase( regFree2==0 );

       break;

     }

     case TK_UMINUS: {

       Expr *pLeft = pExpr->pLeft;

       assert( pLeft );

       if( pLeft->op==TK_FLOAT || pLeft->op==TK_INTEGER ){

         if( pLeft->op==TK_FLOAT ){

           codeReal(v, (char*)pLeft->token.z, pLeft->token.n, 1, target);

         }else{

           codeInteger(v, pLeft, 1, target);

         }

       }else{

         regFree1 = r1 = sqlite3GetTempReg(pParse);

         sqlite3VdbeAddOp2(v, OP_Integer, 0, r1);

         r2 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree2);

         sqlite3VdbeAddOp3(v, OP_Subtract, r2, r1, target);

         testcase( regFree2==0 );

       }

       inReg = target;

       break;

     }

     case TK_BITNOT:

     case TK_NOT: {

       assert( TK_BITNOT==OP_BitNot );

       assert( TK_NOT==OP_Not );

       testcase( op==TK_BITNOT );

       testcase( op==TK_NOT );

       inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);

       testcase( inReg==target );

       testcase( usedAsColumnCache(pParse, inReg, inReg) );

       inReg = sqlite3ExprWritableRegister(pParse, inReg, target);

       sqlite3VdbeAddOp1(v, op, inReg);

       break;

     }

     case TK_ISNULL:

     case TK_NOTNULL: {

       int addr;

       assert( TK_ISNULL==OP_IsNull );

       assert( TK_NOTNULL==OP_NotNull );

       testcase( op==TK_ISNULL );

       testcase( op==TK_NOTNULL );

       sqlite3VdbeAddOp2(v, OP_Integer, 1, target);

       r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);

       testcase( regFree1==0 );

       addr = sqlite3VdbeAddOp1(v, op, r1);

       sqlite3VdbeAddOp2(v, OP_AddImm, target, -1);

       sqlite3VdbeJumpHere(v, addr);

       break;

     }

     case TK_AGG_FUNCTION: {

       AggInfo *pInfo = pExpr->pAggInfo;

       if( pInfo==0 ){

         sqlite3ErrorMsg(pParse, "misuse of aggregate: %T",

             &pExpr->span);

       }else{

         inReg = pInfo->aFunc[pExpr->iAgg].iMem;

       }

       break;

     }

     case TK_CONST_FUNC:

     case TK_FUNCTION: {

       ExprList *pList = pExpr->pList;

       int nExpr = pList ? pList->nExpr : 0;

       FuncDef *pDef;

       int nId;

       const char *zId;

       int constMask = 0;

       int i;

       sqlite3 *db = pParse->db;

       u8 enc = ENC(db);

       CollSeq *pColl = 0;

       testcase( op==TK_CONST_FUNC );

       testcase( op==TK_FUNCTION );

       zId = (char*)pExpr->token.z;

       nId = pExpr->token.n;

       pDef = sqlite3FindFunction(pParse->db, zId, nId, nExpr, enc, 0);

       assert( pDef!=0 );

       if( pList ){

         nExpr = pList->nExpr;

         r1 = sqlite3GetTempRange(pParse, nExpr);

         sqlite3ExprCodeExprList(pParse, pList, r1, 1);

       }else{

         nExpr = r1 = 0;

       }

 #ifndef SQLITE_OMIT_VIRTUALTABLE

       /* Possibly overload the function if the first argument is

       ** a virtual table column.

       **

       ** For infix functions (LIKE, GLOB, REGEXP, and MATCH) use the

       ** second argument, not the first, as the argument to test to

       ** see if it is a column in a virtual table.  This is done because

       ** the left operand of infix functions (the operand we want to

       ** control overloading) ends up as the second argument to the

       ** function.  The expression "A glob B" is equivalent to 

       ** "glob(B,A).  We want to use the A in "A glob B" to test

       ** for function overloading.  But we use the B term in "glob(B,A)".

       */

       if( nExpr>=2 && (pExpr->flags & EP_InfixFunc) ){

         pDef = sqlite3VtabOverloadFunction(db, pDef, nExpr, pList->a[1].pExpr);

       }else if( nExpr>0 ){

         pDef = sqlite3VtabOverloadFunction(db, pDef, nExpr, pList->a[0].pExpr);

       }

 #endif

       for(i=0; i<nExpr && i<32; i++){

         if( sqlite3ExprIsConstant(pList->a[i].pExpr) ){

           constMask |= (1<<i);

         }

         if( pDef->needCollSeq && !pColl ){

           pColl = sqlite3ExprCollSeq(pParse, pList->a[i].pExpr);

         }

       }

       if( pDef->needCollSeq ){

         if( !pColl ) pColl = pParse->db->pDfltColl; 

         sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);

       }

       sqlite3VdbeAddOp4(v, OP_Function, constMask, r1, target,

                         (char*)pDef, P4_FUNCDEF);

       sqlite3VdbeChangeP5(v, nExpr);

       if( nExpr ){

         sqlite3ReleaseTempRange(pParse, r1, nExpr);

       }

       sqlite3ExprCacheAffinityChange(pParse, r1, nExpr);

       break;

     }

 #ifndef SQLITE_OMIT_SUBQUERY

     case TK_EXISTS:

     case TK_SELECT: {

       testcase( op==TK_EXISTS );

       testcase( op==TK_SELECT );

       if( pExpr->iColumn==0 ){

         sqlite3CodeSubselect(pParse, pExpr, 0);

       }

       inReg = pExpr->iColumn;

       break;

     }

     case TK_IN: {

       int rNotFound = 0;

       int rMayHaveNull = 0;

       int j2, j3, j4, j5;

       char affinity;

       int eType;

       VdbeNoopComment((v, "begin IN expr r%d", target));

       eType = sqlite3FindInIndex(pParse, pExpr, &rMayHaveNull);

       if( rMayHaveNull ){

         rNotFound = ++pParse->nMem;

       }

       /* Figure out the affinity to use to create a key from the results

       ** of the expression. affinityStr stores a static string suitable for

       ** P4 of OP_MakeRecord.

       */

       affinity = comparisonAffinity(pExpr);

       /* Code the <expr> from "<expr> IN (...)". The temporary table

       ** pExpr->iTable contains the values that make up the (...) set.

       */

       pParse->disableColCache++;

       sqlite3ExprCode(pParse, pExpr->pLeft, target);

       pParse->disableColCache--;

       j2 = sqlite3VdbeAddOp1(v, OP_IsNull, target);

       if( eType==IN_INDEX_ROWID ){

         j3 = sqlite3VdbeAddOp1(v, OP_MustBeInt, target);

         j4 = sqlite3VdbeAddOp3(v, OP_NotExists, pExpr->iTable, 0, target);

         sqlite3VdbeAddOp2(v, OP_Integer, 1, target);

         j5 = sqlite3VdbeAddOp0(v, OP_Goto);

         sqlite3VdbeJumpHere(v, j3);

         sqlite3VdbeJumpHere(v, j4);

         sqlite3VdbeAddOp2(v, OP_Integer, 0, target);

       }else{

         r2 = regFree2 = sqlite3GetTempReg(pParse);

         /* Create a record and test for set membership. If the set contains

         ** the value, then jump to the end of the test code. The target

         ** register still contains the true (1) value written to it earlier.

         */

         sqlite3VdbeAddOp4(v, OP_MakeRecord, target, 1, r2, &affinity, 1);

         sqlite3VdbeAddOp2(v, OP_Integer, 1, target);

         j5 = sqlite3VdbeAddOp3(v, OP_Found, pExpr->iTable, 0, r2);

         /* If the set membership test fails, then the result of the 

         ** "x IN (...)" expression must be either 0 or NULL. If the set

         ** contains no NULL values, then the result is 0. If the set 

         ** contains one or more NULL values, then the result of the

         ** expression is also NULL.

         */

         if( rNotFound==0 ){

           /* This branch runs if it is known at compile time (now) that 

           ** the set contains no NULL values. This happens as the result

           ** of a "NOT NULL" constraint in the database schema. No need

           ** to test the data structure at runtime in this case.

           */

           sqlite3VdbeAddOp2(v, OP_Integer, 0, target);

         }else{

           /* This block populates the rNotFound register with either NULL

           ** or 0 (an integer value). If the data structure contains one

           ** or more NULLs, then set rNotFound to NULL. Otherwise, set it

           ** to 0. If register rMayHaveNull is already set to some value

           ** other than NULL, then the test has already been run and 

           ** rNotFound is already populated.

           */

           static const char nullRecord[] = { 0x02, 0x00 };

           j3 = sqlite3VdbeAddOp1(v, OP_NotNull, rMayHaveNull);

           sqlite3VdbeAddOp2(v, OP_Null, 0, rNotFound);

           sqlite3VdbeAddOp4(v, OP_Blob, 2, rMayHaveNull, 0, 

                              nullRecord, P4_STATIC);

           j4 = sqlite3VdbeAddOp3(v, OP_Found, pExpr->iTable, 0, rMayHaveNull);

           sqlite3VdbeAddOp2(v, OP_Integer, 0, rNotFound);

           sqlite3VdbeJumpHere(v, j4);