/*

 ** 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 1.399 2008/10/11 16:47:36 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

   if( (op==TK_COLUMN || op==TK_REGISTER) && pExpr->pTab!=0 ){

     /* op==TK_REGISTER && pExpr->pTab!=0 happens when pExpr was originally

     ** a TK_COLUMN but was previously evaluated and cached in a register */

     int j = pExpr->iColumn;

     if( j<0 ) return SQLITE_AFF_INTEGER;

     assert( pExpr->pTab && j<pExpr->pTab->nCol );

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

   }

   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 *pCollName){

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

   CollSeq *pColl;

   sqlite3 *db = pParse->db;

   zColl = sqlite3NameFromToken(db, pCollName);

   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;

   Expr *p = pExpr;

   while( p ){

     int op;

     pColl = p->pColl;

     if( pColl ) break;

     op = p->op;

     if( (op==TK_COLUMN || op==TK_REGISTER) && p->pTab!=0 ){

       /* op==TK_REGISTER && p->pTab!=0 happens when pExpr was originally

       ** a TK_COLUMN but was previously evaluated and cached in a register */

       const char *zColl;

       int j = p->iColumn;

       if( j>=0 ){

         sqlite3 *db = pParse->db;

         zColl = p->pTab->aCol[j].zColl;

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

         pExpr->pColl = pColl;

       }

       break;

     }

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

       break;

     }

     p = p->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.

 */

 int sqlite3ExprCheckHeight(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);

   sqlite3ExprCheckHeight(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 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 ){

     sqlite3ExprCheckHeight(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");

   }

 }

 /*

 ** Clear an expression structure without deleting the structure itself.

 ** Substructure is deleted.

 */

 void sqlite3ExprClear(sqlite3 *db, Expr *p){

   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);

 }

 /*

 ** Recursively delete an expression tree.

 */

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

   if( p==0 ) return;

   sqlite3ExprClear(db, p);

   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->done = 0;

     pItem->iCol = pOldItem->iCol;

     pItem->iAlias = pOldItem->iAlias;

   }

   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;

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

     pNewItem->notIndexed = pOldItem->notIndexed;

     pNewItem->pIndex = pOldItem->pIndex;

     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->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->selFlags = p->selFlags & ~SF_UsesEphemeral;

   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;

     pItem->iAlias = 0;

   }

   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);

 }

 /*

 ** These routines are Walker callbacks.  Walker.u.pi is a pointer

 ** to an integer.  These routines are checking an expression to see

 ** if it is a constant.  Set *Walker.u.pi to 0 if the expression is

 ** not constant.

 **

 ** These callback routines are used to implement the following:

 **

 **     sqlite3ExprIsConstant()

 **     sqlite3ExprIsConstantNotJoin()

 **     sqlite3ExprIsConstantOrFunction()

 **

 */

 static int exprNodeIsConstant(Walker *pWalker, Expr *pExpr){

   /* If pWalker->u.i 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( pWalker->u.i==3 && ExprHasAnyProperty(pExpr, EP_FromJoin) ){

     pWalker->u.i = 0;

     return WRC_Abort;

   }

   switch( pExpr->op ){

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

     ** and pWalker->u.i==2 */

     case TK_FUNCTION:

       if( pWalker->u.i==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 );

       pWalker->u.i = 0;

       return WRC_Abort;

     default:

       return WRC_Continue;

   }

 }

 static int selectNodeIsConstant(Walker *pWalker, Select *pSelect){

   pWalker->u.i = 0;

   return WRC_Abort;

 }

 static int exprIsConst(Expr *p, int initFlag){

   Walker w;

   w.u.i = initFlag;

   w.xExprCallback = exprNodeIsConstant;

   w.xSelectCallback = selectNodeIsConstant;

   sqlite3WalkExpr(&w, p);

   return w.u.i;

 }

 /*

 ** 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){

   return exprIsConst(p, 1);

 }

 /*

 ** 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){

   return exprIsConst(p, 3);

 }

 /*

 ** 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){

   return exprIsConst(p, 2);

 }

 /*

 ** 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;

 }

 #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->selFlags & (SF_Distinct|SF_Aggregate) ){

       return 0; /* No DISTINCT keyword and 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;

     eType = IN_INDEX_EPH;

     if( prNotFound ){

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

     }else if( pX->pLeft->iColumn<0 && pX->pSelect==0 ){

       eType = IN_INDEX_ROWID;

     }

     sqlite3CodeSubselect(pParse, pX, rMayHaveNull, eType==IN_INDEX_ROWID);

   }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.

 **

 ** If parameter isRowid is non-zero, then expression pExpr is guaranteed

 ** to be of the form "<rowid> IN (?, ?, ?)", where <rowid> is a reference

 ** to some integer key column of a table B-Tree. In this case, use an

 ** intkey B-Tree to store the set of IN(...) values instead of the usual

 ** (slower) variable length keys B-Tree.

 */

 #ifndef SQLITE_OMIT_SUBQUERY

 void sqlite3CodeSubselect(

   Parse *pParse, 

   Expr *pExpr, 

   int rMayHaveNull,

   int isRowid

 ){

   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 */

       Expr *pLeft = pExpr->pLeft;

       if( rMayHaveNull ){

         sqlite3VdbeAddOp2(v, OP_Null, 0, rMayHaveNull);

       }

       affinity = sqlite3ExprAffinity(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, !isRowid);

       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;

         assert( !isRowid );

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

         dest.affinity = (int)affinity;

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

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

           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] = sqlite3ExprCollSeq(pParse, pExpr->pLeft);

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

         r1 = sqlite3GetTempReg(pParse);

         r2 = sqlite3GetTempReg(pParse);

         sqlite3VdbeAddOp2(v, OP_Null, 0, r2);

         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--;

           if( isRowid ){

             sqlite3VdbeAddOp2(v, OP_MustBeInt, r3, sqlite3VdbeCurrentAddr(v)+2);

             sqlite3VdbeAddOp3(v, OP_Insert, pExpr->iTable, r2, r3);

           }else{

             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);

       }

       if( !isRowid ){

         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) ){

         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 to store the value of the iAlias-th alias in register

 ** target.  The first time this is called, pExpr is evaluated to compute

 ** the value of the alias.  The value is stored in an auxiliary register

 ** and the number of that register is returned.  On subsequent calls,

 ** the register number is returned without generating any code.

 **

 ** Note that in order for this to work, code must be generated in the

 ** same order that it is executed.

 **

 ** Aliases are numbered starting with 1.  So iAlias is in the range

 ** of 1 to pParse->nAlias inclusive.  

 **

 ** pParse->aAlias[iAlias-1] records the register number where the value

 ** of the iAlias-th alias is stored.  If zero, that means that the

 ** alias has not yet been computed.

 */

 static int codeAlias(Parse *pParse, int iAlias, Expr *pExpr, int target){

   sqlite3 *db = pParse->db;

   int iReg;

   if( pParse->nAliasAlloc<pParse->nAlias ){

     pParse->aAlias = sqlite3DbReallocOrFree(db, pParse->aAlias,

                                   sizeof(pParse->aAlias[0])*pParse->nAlias );

     testcase( db->mallocFailed && pParse->nAliasAlloc>0 );

     if( db->mallocFailed ) return 0;

     memset(&pParse->aAlias[pParse->nAliasAlloc], 0,

            (pParse->nAlias-pParse->nAliasAlloc)*sizeof(pParse->aAlias[0]));

     pParse->nAliasAlloc = pParse->nAlias;

   }

   assert( iAlias>0 && iAlias<=pParse->nAlias );

   iReg = pParse->aAlias[iAlias-1];

   if( iReg==0 ){

     if( pParse->disableColCache ){

       iReg = sqlite3ExprCodeTarget(pParse, pExpr, target);

     }else{

       iReg = ++pParse->nMem;

       sqlite3ExprCode(pParse, pExpr, iReg);

       pParse->aAlias[iAlias-1] = iReg;

     }

   }

   return iReg;

 }

 /*

 ** 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 guarantee 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 */

   sqlite3 *db;

   db = pParse->db;

   assert( v!=0 || 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(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;

     }

     case TK_AS: {

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

       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 );

       if( inReg!=target ){

         sqlite3VdbeAddOp2(v, OP_SCopy, inReg, target);

         inReg = target;

       }

       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 );

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

       testcase( regFree1==0 );

       inReg = target;

       sqlite3VdbeAddOp2(v, op, r1, 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;

       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(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->flags & SQLITE_FUNC_NEEDCOLL)!=0 && !pColl ){

           pColl = sqlite3ExprCollSeq(pParse, pList->a[i].pExpr);

         }

       }

       if( pDef->flags & SQLITE_FUNC_NEEDCOLL ){

         if( !pColl ) pColl = 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, 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);

           sqlite3VdbeJumpHere(v, j3);

           /* Copy the value of register rNotFound (which is either NULL or 0)

           ** into the target register. This will be the result of the

           ** expression.

           */

           sqlite3VdbeAddOp2(v, OP_Copy, rNotFound, target);

         }

       }

       sqlite3VdbeJumpHere(v, j2);

       sqlite3VdbeJumpHere(v, j5);

       VdbeComment((v, "end IN expr r%d", target));

       break;

     }

 #endif

     /*

     **    x BETWEEN y AND z

     **

     ** This is equivalent to

     **

     **    x>=y AND x<=z

     **

     ** X is stored in pExpr->pLeft.

     ** Y is stored in pExpr->pList->a[0].pExpr.

     ** Z is stored in pExpr->pList->a[1].pExpr.

     */

     case TK_BETWEEN: {

       Expr *pLeft = pExpr->pLeft;

       struct ExprList_item *pLItem = pExpr->pList->a;

       Expr *pRight = pLItem->pExpr;

       codeCompareOperands(pParse, pLeft, &r1, &regFree1,

                                   pRight, &r2, &regFree2);

       testcase( regFree1==0 );

       testcase( regFree2==0 );

       r3 = sqlite3GetTempReg(pParse);

       r4 = sqlite3GetTempReg(pParse);

       codeCompare(pParse, pLeft, pRight, OP_Ge,

                   r1, r2, r3, SQLITE_STOREP2);

       pLItem++;

       pRight = pLItem->pExpr;

       sqlite3ReleaseTempReg(pParse, regFree2);

       r2 = sqlite3ExprCodeTemp(pParse, pRight, &regFree2);

       testcase( regFree2==0 );

       codeCompare(pParse, pLeft, pRight, OP_Le, r1, r2, r4, SQLITE_STOREP2);

       sqlite3VdbeAddOp3(v, OP_And, r3, r4, target);

       sqlite3ReleaseTempReg(pParse, r3);

       sqlite3ReleaseTempReg(pParse, r4);

       break;

     }

     case TK_UPLUS: {

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

       break;

     }

     /*

     ** Form A:

     **   CASE x WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END

     **

     ** Form B:

     **   CASE WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END

     **

     ** Form A is can be transformed into the equivalent form B as follows:

     **   CASE WHEN x=e1 THEN r1 WHEN x=e2 THEN r2 ...

     **        WHEN x=eN THEN rN ELSE y END

     **

     ** X (if it exists) is in pExpr->pLeft.

     ** Y is in pExpr->pRight.  The Y is also optional.  If there is no

     ** ELSE clause and no other term matches, then the result of the

     ** exprssion is NULL.

     ** Ei is in pExpr->pList->a[i*2] and Ri is pExpr->pList->a[i*2+1].

     **

     ** The result of the expression is the Ri for the first matching Ei,

     ** or if there is no matching Ei, the ELSE term Y, or if there is

     ** no ELSE term, NULL.

     */

     case TK_CASE: {

       int endLabel;                     /* GOTO label for end of CASE stmt */

       int nextCase;                     /* GOTO label for next WHEN clause */

       int nExpr;                        /* 2x number of WHEN terms */

       int i;                            /* Loop counter */

       ExprList *pEList;                 /* List of WHEN terms */

       struct ExprList_item *aListelem;  /* Array of WHEN terms */

       Expr opCompare;                   /* The X==Ei expression */

       Expr cacheX;                      /* Cached expression X */

       Expr *pX;                         /* The X expression */

       Expr *pTest;                      /* X==Ei (form A) or just Ei (form B) */

       assert(pExpr->pList);

       assert((pExpr->pList->nExpr % 2) == 0);

       assert(pExpr->pList->nExpr > 0);

       pEList = pExpr->pList;

       aListelem = pEList->a;

       nExpr = pEList->nExpr;

       endLabel = sqlite3VdbeMakeLabel(v);

       if( (pX = pExpr->pLeft)!=0 ){

         cacheX = *pX;

         testcase( pX->op==TK_COLUMN || pX->op==TK_REGISTER );

         cacheX.iTable = sqlite3ExprCodeTemp(pParse, pX, &regFree1);

         testcase( regFree1==0 );

         cacheX.op = TK_REGISTER;

         opCompare.op = TK_EQ;

         opCompare.pLeft = &cacheX;

         pTest = &opCompare;

       }

       pParse->disableColCache++;

       for(i=0; i<nExpr; i=i+2){

         if( pX ){

           opCompare.pRight = aListelem[i].pExpr;

         }else{

           pTest = aListelem[i].pExpr;

         }

         nextCase = sqlite3VdbeMakeLabel(v);

         testcase( pTest->op==TK_COLUMN || pTest->op==TK_REGISTER );

         sqlite3ExprIfFalse(pParse, pTest, nextCase, SQLITE_JUMPIFNULL);

         testcase( aListelem[i+1].pExpr->op==TK_COLUMN );

         testcase( aListelem[i+1].pExpr->op==TK_REGISTER );

         sqlite3ExprCode(pParse, aListelem[i+1].pExpr, target);

         sqlite3VdbeAddOp2(v, OP_Goto, 0, endLabel);

         sqlite3VdbeResolveLabel(v, nextCase);

       }

       if( pExpr->pRight ){

         sqlite3ExprCode(pParse, pExpr->pRight, target);

       }else{

         sqlite3VdbeAddOp2(v, OP_Null, 0, target);

       }

       sqlite3VdbeResolveLabel(v, endLabel);

       assert( pParse->disableColCache>0 );

       pParse->disableColCache--;

       break;

     }

 #ifndef SQLITE_OMIT_TRIGGER

     case TK_RAISE: {

       if( !pParse->trigStack ){

         sqlite3ErrorMsg(pParse,

                        "RAISE() may only be used within a trigger-program");

         return 0;

       }

       if( pExpr->iColumn!=OE_Ignore ){

          assert( pExpr->iColumn==OE_Rollback ||

                  pExpr->iColumn == OE_Abort ||

                  pExpr->iColumn == OE_Fail );

          sqlite3DequoteExpr(db, pExpr);

          sqlite3VdbeAddOp4(v, OP_Halt, SQLITE_CONSTRAINT, pExpr->iColumn, 0,

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

       } else {

          assert( pExpr->iColumn == OE_Ignore );

          sqlite3VdbeAddOp2(v, OP_ContextPop, 0, 0);

          sqlite3VdbeAddOp2(v, OP_Goto, 0, pParse->trigStack->ignoreJump);

          VdbeComment((v, "raise(IGNORE)"));

       }

       break;

     }

 #endif

   }

   sqlite3ReleaseTempReg(pParse, regFree1);

   sqlite3ReleaseTempReg(pParse, regFree2);

   return inReg;

 }

 /*

 ** Generate code to evaluate an expression and store the results

 ** into a register.  Return the register number where the results

 ** are stored.

 **

 ** If the register is a temporary register that can be deallocated,

 ** then write its number into *pReg.  If the result register is not

 ** a temporary, then set *pReg to zero.

 */

 int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){

   int r1 = sqlite3GetTempReg(pParse);

   int r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);

   if( r2==r1 ){

     *pReg = r1;

   }else{

     sqlite3ReleaseTempReg(pParse, r1);

     *pReg = 0;

   }

   return r2;

 }

 /*

 ** Generate code that will evaluate expression pExpr and store the

 ** results in register target.  The results are guaranteed to appear

 ** in register target.

 */

 int sqlite3ExprCode(Parse *pParse, Expr *pExpr, int target){

   int inReg;

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

   inReg = sqlite3ExprCodeTarget(pParse, pExpr, target);

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

   if( inReg!=target && pParse->pVdbe ){

     sqlite3VdbeAddOp2(pParse->pVdbe, OP_SCopy, inReg, target);

   }

   return target;

 }

 /*

 ** Generate code that evalutes the given expression and puts the result

 ** in register target.

 **

 ** Also make a copy of the expression results into another "cache" register

 ** and modify the expression so that the next time it is evaluated,

 ** the result is a copy of the cache register.

 **

 ** This routine is used for expressions that are used multiple 

 ** times.  They are evaluated once and the results of the expression

 ** are reused.

 */

 int sqlite3ExprCodeAndCache(Parse *pParse, Expr *pExpr, int target){

   Vdbe *v = pParse->pVdbe;

   int inReg;

   inReg = sqlite3ExprCode(pParse, pExpr, target);

   assert( target>0 );

   if( pExpr->op!=TK_REGISTER ){  

     int iMem;

     iMem = ++pParse->nMem;

     sqlite3VdbeAddOp2(v, OP_Copy, inReg, iMem);

     pExpr->iTable = iMem;

     pExpr->op = TK_REGISTER;

   }

   return inReg;

 }

 /*

 ** Return TRUE if pExpr is an constant expression that is appropriate

 ** for factoring out of a loop.  Appropriate expressions are:

 **

 **    *  Any expression that evaluates to two or more opcodes.

 **

 **    *  Any OP_Integer, OP_Real, OP_String, OP_Blob, OP_Null, 

 **       or OP_Variable that does not need to be placed in a 

 **       specific register.

 **

 ** There is no point in factoring out single-instruction constant

 ** expressions that need to be placed in a particular register.  

 ** We could factor them out, but then we would end up adding an

 ** OP_SCopy instruction to move the value into the correct register

 ** later.  We might as well just use the original instruction and

 ** avoid the OP_SCopy.

 */

 static int isAppropriateForFactoring(Expr *p){

   if( !sqlite3ExprIsConstantNotJoin(p) ){

     return 0;  /* Only constant expressions are appropriate for factoring */

   }

   if( (p->flags & EP_FixedDest)==0 ){

     return 1;  /* Any constant without a fixed destination is appropriate */

   }

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

   switch( p->op ){

 #ifndef SQLITE_OMIT_BLOB_LITERAL

     case TK_BLOB:

 #endif

     case TK_VARIABLE:

     case TK_INTEGER:

     case TK_FLOAT:

     case TK_NULL:

     case TK_STRING: {

       testcase( p->op==TK_BLOB );

       testcase( p->op==TK_VARIABLE );

       testcase( p->op==TK_INTEGER );

       testcase( p->op==TK_FLOAT );

       testcase( p->op==TK_NULL );

       testcase( p->op==TK_STRING );

       /* Single-instruction constants with a fixed destination are

       ** better done in-line.  If we factor them, they will just end

       ** up generating an OP_SCopy to move the value to the destination

       ** register. */

       return 0;

     }

     case TK_UMINUS: {

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

          return 0;

        }

        break;

     }

     default: {

       break;

     }

   }

   return 1;

 }

 /*

 ** If pExpr is a constant expression that is appropriate for

 ** factoring out of a loop, then evaluate the expression

 ** into a register and convert the expression into a TK_REGISTER

 ** expression.

 */

 static int evalConstExpr(Walker *pWalker, Expr *pExpr){

   Parse *pParse = pWalker->pParse;

   switch( pExpr->op ){

     case TK_REGISTER: {

       return 1;

     }

     case TK_FUNCTION:

     case TK_AGG_FUNCTION:

     case TK_CONST_FUNC: {

       /* The arguments to a function have a fixed destination.

       ** Mark them this way to avoid generated unneeded OP_SCopy

       ** instructions. 

       */

       ExprList *pList = pExpr->pList;

       if( pList ){

         int i = pList->nExpr;

         struct ExprList_item *pItem = pList->a;

         for(; i>0; i--, pItem++){

           if( pItem->pExpr ) pItem->pExpr->flags |= EP_FixedDest;

         }

       }

       break;

     }

   }

   if( isAppropriateForFactoring(pExpr) ){

     int r1 = ++pParse->nMem;

     int r2;

     r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);

     if( r1!=r2 ) sqlite3ReleaseTempReg(pParse, r1);

     pExpr->op = TK_REGISTER;

     pExpr->iTable = r2;

     return WRC_Prune;

   }

   return WRC_Continue;

 }

 /*

 ** Preevaluate constant subexpressions within pExpr and store the

 ** results in registers.  Modify pExpr so that the constant subexpresions

 ** are TK_REGISTER opcodes that refer to the precomputed values.

 */

 void sqlite3ExprCodeConstants(Parse *pParse, Expr *pExpr){

   Walker w;

   w.xExprCallback = evalConstExpr;

   w.xSelectCallback = 0;

   w.pParse = pParse;

   sqlite3WalkExpr(&w, pExpr);

 }

 /*

 ** Generate code that pushes the value of every element of the given

 ** expression list into a sequence of registers beginning at target.

 **

 ** Return the number of elements evaluated.

 */

 int sqlite3ExprCodeExprList(

   Parse *pParse,     /* Parsing context */

   ExprList *pList,   /* The expression list to be coded */

   int target,        /* Where to write results */

   int doHardCopy     /* Make a hard copy of every element */

 ){

   struct ExprList_item *pItem;

   int i, n;

   assert( pList!=0 );

   assert( target>0 );

   n = pList->nExpr;

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

     if( pItem->iAlias ){

       int iReg = codeAlias(pParse, pItem->iAlias, pItem->pExpr, target);

       Vdbe *v = sqlite3GetVdbe(pParse);

       if( iReg!=target+i ){

         sqlite3VdbeAddOp2(v, OP_SCopy, iReg, target+i);

       }

     }else{

       sqlite3ExprCode(pParse, pItem->pExpr, target+i);

     }

     if( doHardCopy ){

       sqlite3ExprHardCopy(pParse, target, n);

     }

   }

   return n;

 }

 /*

 ** Generate code for a boolean expression such that a jump is made

 ** to the label "dest" if the expression is true but execution

 ** continues straight thru if the expression is false.

 **

 ** If the expression evaluates to NULL (neither true nor false), then

 ** take the jump if the jumpIfNull flag is SQLITE_JUMPIFNULL.

 **

 ** This code depends on the fact that certain token values (ex: TK_EQ)

 ** are the same as opcode values (ex: OP_Eq) that implement the corresponding

 ** operation.  Special comments in vdbe.c and the mkopcodeh.awk script in

 ** the make process cause these values to align.  Assert()s in the code

 ** below verify that the numbers are aligned correctly.

 */

 void sqlite3ExprIfTrue(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){

   Vdbe *v = pParse->pVdbe;

   int op = 0;

   int regFree1 = 0;

   int regFree2 = 0;

   int r1, r2;

   assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );

   if( v==0 || pExpr==0 ) return;

   op = pExpr->op;

   switch( op ){

     case TK_AND: {

       int d2 = sqlite3VdbeMakeLabel(v);

       testcase( jumpIfNull==0 );

       testcase( pParse->disableColCache==0 );

       sqlite3ExprIfFalse(pParse, pExpr->pLeft, d2,jumpIfNull^SQLITE_JUMPIFNULL);

       pParse->disableColCache++;

       sqlite3ExprIfTrue(pParse, pExpr->pRight, dest, jumpIfNull);

       assert( pParse->disableColCache>0 );

       pParse->disableColCache--;

       sqlite3VdbeResolveLabel(v, d2);

       break;

     }

     case TK_OR: {

       testcase( jumpIfNull==0 );

       testcase( pParse->disableColCache==0 );

       sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);

       pParse->disableColCache++;

       sqlite3ExprIfTrue(pParse, pExpr->pRight, dest, jumpIfNull);

       assert( pParse->disableColCache>0 );

       pParse->disableColCache--;

       break;

     }

     case TK_NOT: {

       testcase( jumpIfNull==0 );

       sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);

       break;

     }

     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 );

       testcase( jumpIfNull==0 );

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

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

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

                   r1, r2, dest, jumpIfNull);

       testcase( regFree1==0 );

       testcase( regFree2==0 );

       break;

     }

     case TK_ISNULL:

     case TK_NOTNULL: {

       assert( TK_ISNULL==OP_IsNull );

       assert( TK_NOTNULL==OP_NotNull );

       testcase( op==TK_ISNULL );

       testcase( op==TK_NOTNULL );

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

       sqlite3VdbeAddOp2(v, op, r1, dest);

       testcase( regFree1==0 );

       break;

     }

     case TK_BETWEEN: {

       /*    x BETWEEN y AND z

       **

       ** Is equivalent to 

       **

       **    x>=y AND x<=z

       **

       ** Code it as such, taking care to do the common subexpression

       ** elementation of x.

       */

       Expr exprAnd;

       Expr compLeft;

       Expr compRight;

       Expr exprX;

       exprX = *pExpr->pLeft;

       exprAnd.op = TK_AND;

       exprAnd.pLeft = &compLeft;

       exprAnd.pRight = &compRight;

       compLeft.op = TK_GE;

       compLeft.pLeft = &exprX;

       compLeft.pRight = pExpr->pList->a[0].pExpr;

       compRight.op = TK_LE;

       compRight.pLeft = &exprX;

       compRight.pRight = pExpr->pList->a[1].pExpr;

       exprX.iTable = sqlite3ExprCodeTemp(pParse, &exprX, &regFree1);

       testcase( regFree1==0 );

       exprX.op = TK_REGISTER;

       testcase( jumpIfNull==0 );

       sqlite3ExprIfTrue(pParse, &exprAnd, dest, jumpIfNull);

       break;

     }

     default: {

       r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);

       sqlite3VdbeAddOp3(v, OP_If, r1, dest, jumpIfNull!=0);