/*

 ** 2005 February 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 C code routines that used to generate VDBE code

 ** that implements the ALTER TABLE command.

 **

 ** $Id: alter.c,v 1.48 2008/08/08 14:19:41 drh Exp $

 */

 #include "sqliteInt.h"

 #include <ctype.h>

 /*

 ** The code in this file only exists if we are not omitting the

 ** ALTER TABLE logic from the build.

 */

 #ifndef SQLITE_OMIT_ALTERTABLE

 /*

 ** This function is used by SQL generated to implement the 

 ** ALTER TABLE command. The first argument is the text of a CREATE TABLE or

 ** CREATE INDEX command. The second is a table name. The table name in 

 ** the CREATE TABLE or CREATE INDEX statement is replaced with the third

 ** argument and the result returned. Examples:

 **

 ** sqlite_rename_table('CREATE TABLE abc(a, b, c)', 'def')

 **     -> 'CREATE TABLE def(a, b, c)'

 **

 ** sqlite_rename_table('CREATE INDEX i ON abc(a)', 'def')

 **     -> 'CREATE INDEX i ON def(a, b, c)'

 */

 static void renameTableFunc(

   sqlite3_context *context,

   int argc,

   sqlite3_value **argv

 ){

   unsigned char const *zSql = sqlite3_value_text(argv[0]);

   unsigned char const *zTableName = sqlite3_value_text(argv[1]);

   int token;

   Token tname;

   unsigned char const *zCsr = zSql;

   int len = 0;

   char *zRet;

   sqlite3 *db = sqlite3_context_db_handle(context);

   /* The principle used to locate the table name in the CREATE TABLE 

   ** statement is that the table name is the first non-space token that

   ** is immediately followed by a TK_LP or TK_USING token.

   */

   if( zSql ){

     do {

       if( !*zCsr ){

         /* Ran out of input before finding an opening bracket. Return NULL. */

         return;

       }

       /* Store the token that zCsr points to in tname. */

       tname.z = zCsr;

       tname.n = len;

       /* Advance zCsr to the next token. Store that token type in 'token',

       ** and its length in 'len' (to be used next iteration of this loop).

       */

       do {

         zCsr += len;

         len = sqlite3GetToken(zCsr, &token);

       } while( token==TK_SPACE );

       assert( len>0 );

     } while( token!=TK_LP && token!=TK_USING );

     zRet = sqlite3MPrintf(db, "%.*s\"%w\"%s", tname.z - zSql, zSql, 

        zTableName, tname.z+tname.n);

     sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);

   }

 }

 #ifndef SQLITE_OMIT_TRIGGER

 /* This function is used by SQL generated to implement the

 ** ALTER TABLE command. The first argument is the text of a CREATE TRIGGER 

 ** statement. The second is a table name. The table name in the CREATE 

 ** TRIGGER statement is replaced with the third argument and the result 

 ** returned. This is analagous to renameTableFunc() above, except for CREATE

 ** TRIGGER, not CREATE INDEX and CREATE TABLE.

 */

 static void renameTriggerFunc(

   sqlite3_context *context,

   int argc,

   sqlite3_value **argv

 ){

   unsigned char const *zSql = sqlite3_value_text(argv[0]);

   unsigned char const *zTableName = sqlite3_value_text(argv[1]);

   int token;

   Token tname;

   int dist = 3;

   unsigned char const *zCsr = zSql;

   int len = 0;

   char *zRet;

   sqlite3 *db = sqlite3_context_db_handle(context);

   /* The principle used to locate the table name in the CREATE TRIGGER 

   ** statement is that the table name is the first token that is immediatedly

   ** preceded by either TK_ON or TK_DOT and immediatedly followed by one

   ** of TK_WHEN, TK_BEGIN or TK_FOR.

   */

   if( zSql ){

     do {

       if( !*zCsr ){

         /* Ran out of input before finding the table name. Return NULL. */

         return;

       }

       /* Store the token that zCsr points to in tname. */

       tname.z = zCsr;

       tname.n = len;

       /* Advance zCsr to the next token. Store that token type in 'token',

       ** and its length in 'len' (to be used next iteration of this loop).

       */

       do {

         zCsr += len;

         len = sqlite3GetToken(zCsr, &token);

       }while( token==TK_SPACE );

       assert( len>0 );

       /* Variable 'dist' stores the number of tokens read since the most

       ** recent TK_DOT or TK_ON. This means that when a WHEN, FOR or BEGIN 

       ** token is read and 'dist' equals 2, the condition stated above

       ** to be met.

       **

       ** Note that ON cannot be a database, table or column name, so

       ** there is no need to worry about syntax like 

       ** "CREATE TRIGGER ... ON ON.ON BEGIN ..." etc.

       */

       dist++;

       if( token==TK_DOT || token==TK_ON ){

         dist = 0;

       }

     } while( dist!=2 || (token!=TK_WHEN && token!=TK_FOR && token!=TK_BEGIN) );

     /* Variable tname now contains the token that is the old table-name

     ** in the CREATE TRIGGER statement.

     */

     zRet = sqlite3MPrintf(db, "%.*s\"%w\"%s", tname.z - zSql, zSql, 

        zTableName, tname.z+tname.n);

     sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);

   }

 }

 #endif   /* !SQLITE_OMIT_TRIGGER */

 /*

 ** Register built-in functions used to help implement ALTER TABLE

 */

 void sqlite3AlterFunctions(sqlite3 *db){

   sqlite3CreateFunc(db, "sqlite_rename_table", 2, SQLITE_UTF8, 0,

                          renameTableFunc, 0, 0);

 #ifndef SQLITE_OMIT_TRIGGER

   sqlite3CreateFunc(db, "sqlite_rename_trigger", 2, SQLITE_UTF8, 0,

                          renameTriggerFunc, 0, 0);

 #endif

 }

 /*

 ** Generate the text of a WHERE expression which can be used to select all

 ** temporary triggers on table pTab from the sqlite_temp_master table. If

 ** table pTab has no temporary triggers, or is itself stored in the 

 ** temporary database, NULL is returned.

 */

 static char *whereTempTriggers(Parse *pParse, Table *pTab){

   Trigger *pTrig;

   char *zWhere = 0;

   char *tmp = 0;

   const Schema *pTempSchema = pParse->db->aDb[1].pSchema; /* Temp db schema */

   /* If the table is not located in the temp-db (in which case NULL is 

   ** returned, loop through the tables list of triggers. For each trigger

   ** that is not part of the temp-db schema, add a clause to the WHERE 

   ** expression being built up in zWhere.

   */

   if( pTab->pSchema!=pTempSchema ){

     sqlite3 *db = pParse->db;

     for( pTrig=pTab->pTrigger; pTrig; pTrig=pTrig->pNext ){

       if( pTrig->pSchema==pTempSchema ){

         if( !zWhere ){

           zWhere = sqlite3MPrintf(db, "name=%Q", pTrig->name);

         }else{

           tmp = zWhere;

           zWhere = sqlite3MPrintf(db, "%s OR name=%Q", zWhere, pTrig->name);

           sqlite3DbFree(db, tmp);

         }

       }

     }

   }

   return zWhere;

 }

 /*

 ** Generate code to drop and reload the internal representation of table

 ** pTab from the database, including triggers and temporary triggers.

 ** Argument zName is the name of the table in the database schema at

 ** the time the generated code is executed. This can be different from

 ** pTab->zName if this function is being called to code part of an 

 ** "ALTER TABLE RENAME TO" statement.

 */

 static void reloadTableSchema(Parse *pParse, Table *pTab, const char *zName){

   Vdbe *v;

   char *zWhere;

   int iDb;                   /* Index of database containing pTab */

 #ifndef SQLITE_OMIT_TRIGGER

   Trigger *pTrig;

 #endif

   v = sqlite3GetVdbe(pParse);

   if( !v ) return;

   assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );

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

   assert( iDb>=0 );

 #ifndef SQLITE_OMIT_TRIGGER

   /* Drop any table triggers from the internal schema. */

   for(pTrig=pTab->pTrigger; pTrig; pTrig=pTrig->pNext){

     int iTrigDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);

     assert( iTrigDb==iDb || iTrigDb==1 );

     sqlite3VdbeAddOp4(v, OP_DropTrigger, iTrigDb, 0, 0, pTrig->name, 0);

   }

 #endif

   /* Drop the table and index from the internal schema */

   sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);

   /* Reload the table, index and permanent trigger schemas. */

   zWhere = sqlite3MPrintf(pParse->db, "tbl_name=%Q", zName);

   if( !zWhere ) return;

   sqlite3VdbeAddOp4(v, OP_ParseSchema, iDb, 0, 0, zWhere, P4_DYNAMIC);

 #ifndef SQLITE_OMIT_TRIGGER

   /* Now, if the table is not stored in the temp database, reload any temp 

   ** triggers. Don't use IN(...) in case SQLITE_OMIT_SUBQUERY is defined. 

   */

   if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){

     sqlite3VdbeAddOp4(v, OP_ParseSchema, 1, 0, 0, zWhere, P4_DYNAMIC);

   }

 #endif

 }

 /*

 ** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy" 

 ** command. 

 */

 void sqlite3AlterRenameTable(

   Parse *pParse,            /* Parser context. */

   SrcList *pSrc,            /* The table to rename. */

   Token *pName              /* The new table name. */

 ){

   int iDb;                  /* Database that contains the table */

   char *zDb;                /* Name of database iDb */

   Table *pTab;              /* Table being renamed */

   char *zName = 0;          /* NULL-terminated version of pName */ 

   sqlite3 *db = pParse->db; /* Database connection */

   int nTabName;             /* Number of UTF-8 characters in zTabName */

   const char *zTabName;     /* Original name of the table */

   Vdbe *v;

 #ifndef SQLITE_OMIT_TRIGGER

   char *zWhere = 0;         /* Where clause to locate temp triggers */

 #endif

   int isVirtualRename = 0;  /* True if this is a v-table with an xRename() */

   if( db->mallocFailed ) goto exit_rename_table;

   assert( pSrc->nSrc==1 );

   assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );

   pTab = sqlite3LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);

   if( !pTab ) goto exit_rename_table;

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

   zDb = db->aDb[iDb].zName;

   /* Get a NULL terminated version of the new table name. */

   zName = sqlite3NameFromToken(db, pName);

   if( !zName ) goto exit_rename_table;

   /* Check that a table or index named 'zName' does not already exist

   ** in database iDb. If so, this is an error.

   */

   if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){

     sqlite3ErrorMsg(pParse, 

         "there is already another table or index with this name: %s", zName);

     goto exit_rename_table;

   }

   /* Make sure it is not a system table being altered, or a reserved name

   ** that the table is being renamed to.

   */

   if( strlen(pTab->zName)>6 && 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) ){

     sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);

     goto exit_rename_table;

   }

   if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){

     goto exit_rename_table;

   }

 #ifndef SQLITE_OMIT_VIEW

   if( pTab->pSelect ){

     sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);

     goto exit_rename_table;

   }

 #endif

 #ifndef SQLITE_OMIT_AUTHORIZATION

   /* Invoke the authorization callback. */

   if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){

     goto exit_rename_table;

   }

 #endif

 #ifndef SQLITE_OMIT_VIRTUALTABLE

   if( sqlite3ViewGetColumnNames(pParse, pTab) ){

     goto exit_rename_table;

   }

   if( IsVirtual(pTab) && pTab->pMod->pModule->xRename ){

     isVirtualRename = 1;

   }

 #endif

   /* Begin a transaction and code the VerifyCookie for database iDb. 

   ** Then modify the schema cookie (since the ALTER TABLE modifies the

   ** schema). Open a statement transaction if the table is a virtual

   ** table.

   */

   v = sqlite3GetVdbe(pParse);

   if( v==0 ){

     goto exit_rename_table;

   }

   sqlite3BeginWriteOperation(pParse, isVirtualRename, iDb);

   sqlite3ChangeCookie(pParse, iDb);

   /* If this is a virtual table, invoke the xRename() function if

   ** one is defined. The xRename() callback will modify the names

   ** of any resources used by the v-table implementation (including other

   ** SQLite tables) that are identified by the name of the virtual table.

   */

 #ifndef SQLITE_OMIT_VIRTUALTABLE

   if( isVirtualRename ){

     int i = ++pParse->nMem;

     sqlite3VdbeAddOp4(v, OP_String8, 0, i, 0, zName, 0);

     sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pTab->pVtab, P4_VTAB);

   }

 #endif

   /* figure out how many UTF-8 characters are in zName */

   zTabName = pTab->zName;

   nTabName = sqlite3Utf8CharLen(zTabName, -1);

   /* Modify the sqlite_master table to use the new table name. */

   sqlite3NestedParse(pParse,

       "UPDATE %Q.%s SET "

 #ifdef SQLITE_OMIT_TRIGGER

           "sql = sqlite_rename_table(sql, %Q), "

 #else

           "sql = CASE "

             "WHEN type = 'trigger' THEN sqlite_rename_trigger(sql, %Q)"

             "ELSE sqlite_rename_table(sql, %Q) END, "

 #endif

           "tbl_name = %Q, "

           "name = CASE "

             "WHEN type='table' THEN %Q "

             "WHEN name LIKE 'sqlite_autoindex%%' AND type='index' THEN "

              "'sqlite_autoindex_' || %Q || substr(name,%d+18) "

             "ELSE name END "

       "WHERE tbl_name=%Q AND "

           "(type='table' OR type='index' OR type='trigger');", 

       zDb, SCHEMA_TABLE(iDb), zName, zName, zName, 

 #ifndef SQLITE_OMIT_TRIGGER

       zName,

 #endif

       zName, nTabName, zTabName

   );

 #ifndef SQLITE_OMIT_AUTOINCREMENT

   /* If the sqlite_sequence table exists in this database, then update 

   ** it with the new table name.

   */

   if( sqlite3FindTable(db, "sqlite_sequence", zDb) ){

     sqlite3NestedParse(pParse,

         "UPDATE \"%w\".sqlite_sequence set name = %Q WHERE name = %Q",

         zDb, zName, pTab->zName);

   }

 #endif

 #ifndef SQLITE_OMIT_TRIGGER

   /* If there are TEMP triggers on this table, modify the sqlite_temp_master

   ** table. Don't do this if the table being ALTERed is itself located in

   ** the temp database.

   */

   if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){

     sqlite3NestedParse(pParse, 

         "UPDATE sqlite_temp_master SET "

             "sql = sqlite_rename_trigger(sql, %Q), "

             "tbl_name = %Q "

             "WHERE %s;", zName, zName, zWhere);

     sqlite3DbFree(db, zWhere);

   }

 #endif

   /* Drop and reload the internal table schema. */

   reloadTableSchema(pParse, pTab, zName);

 exit_rename_table:

   sqlite3SrcListDelete(db, pSrc);

   sqlite3DbFree(db, zName);

 }

 /*

 ** This function is called after an "ALTER TABLE ... ADD" statement

 ** has been parsed. Argument pColDef contains the text of the new

 ** column definition.

 **

 ** The Table structure pParse->pNewTable was extended to include

 ** the new column during parsing.

 */

 void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){

   Table *pNew;              /* Copy of pParse->pNewTable */

   Table *pTab;              /* Table being altered */

   int iDb;                  /* Database number */

   const char *zDb;          /* Database name */

   const char *zTab;         /* Table name */

   char *zCol;               /* Null-terminated column definition */

   Column *pCol;             /* The new column */

   Expr *pDflt;              /* Default value for the new column */

   sqlite3 *db;              /* The database connection; */

   if( pParse->nErr ) return;

   pNew = pParse->pNewTable;

   assert( pNew );

   db = pParse->db;

   assert( sqlite3BtreeHoldsAllMutexes(db) );

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

   zDb = db->aDb[iDb].zName;

   zTab = pNew->zName;

   pCol = &pNew->aCol[pNew->nCol-1];

   pDflt = pCol->pDflt;

   pTab = sqlite3FindTable(db, zTab, zDb);

   assert( pTab );

 #ifndef SQLITE_OMIT_AUTHORIZATION

   /* Invoke the authorization callback. */

   if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){

     return;

   }

 #endif

   /* If the default value for the new column was specified with a 

   ** literal NULL, then set pDflt to 0. This simplifies checking

   ** for an SQL NULL default below.

   */

   if( pDflt && pDflt->op==TK_NULL ){

     pDflt = 0;

   }

   /* Check that the new column is not specified as PRIMARY KEY or UNIQUE.

   ** If there is a NOT NULL constraint, then the default value for the

   ** column must not be NULL.

   */

   if( pCol->isPrimKey ){

     sqlite3ErrorMsg(pParse, "Cannot add a PRIMARY KEY column");

     return;

   }

   if( pNew->pIndex ){

     sqlite3ErrorMsg(pParse, "Cannot add a UNIQUE column");

     return;

   }

   if( pCol->notNull && !pDflt ){

     sqlite3ErrorMsg(pParse, 

         "Cannot add a NOT NULL column with default value NULL");

     return;

   }

   /* Ensure the default expression is something that sqlite3ValueFromExpr()

   ** can handle (i.e. not CURRENT_TIME etc.)

   */

   if( pDflt ){

     sqlite3_value *pVal;

     if( sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_NONE, &pVal) ){

       db->mallocFailed = 1;

       return;

     }

     if( !pVal ){

       sqlite3ErrorMsg(pParse, "Cannot add a column with non-constant default");

       return;

     }

     sqlite3ValueFree(pVal);

   }

   /* Modify the CREATE TABLE statement. */

   zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);

   if( zCol ){

     char *zEnd = &zCol[pColDef->n-1];

     while( (zEnd>zCol && *zEnd==';') || isspace(*(unsigned char *)zEnd) ){

       *zEnd-- = '\0';

     }

     sqlite3NestedParse(pParse, 

         "UPDATE \"%w\".%s SET "

           "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "

         "WHERE type = 'table' AND name = %Q", 

       zDb, SCHEMA_TABLE(iDb), pNew->addColOffset, zCol, pNew->addColOffset+1,

       zTab

     );

     sqlite3DbFree(db, zCol);

   }

   /* If the default value of the new column is NULL, then set the file

   ** format to 2. If the default value of the new column is not NULL,

   ** the file format becomes 3.

   */

   sqlite3MinimumFileFormat(pParse, iDb, pDflt ? 3 : 2);

   /* Reload the schema of the modified table. */

   reloadTableSchema(pParse, pTab, pTab->zName);

 }

 /*

 ** This function is called by the parser after the table-name in

 ** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument 

 ** pSrc is the full-name of the table being altered.

 **

 ** This routine makes a (partial) copy of the Table structure

 ** for the table being altered and sets Parse.pNewTable to point

 ** to it. Routines called by the parser as the column definition

 ** is parsed (i.e. sqlite3AddColumn()) add the new Column data to 

 ** the copy. The copy of the Table structure is deleted by tokenize.c 

 ** after parsing is finished.

 **

 ** Routine sqlite3AlterFinishAddColumn() will be called to complete

 ** coding the "ALTER TABLE ... ADD" statement.

 */

 void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){

   Table *pNew;

   Table *pTab;

   Vdbe *v;

   int iDb;

   int i;

   int nAlloc;

   sqlite3 *db = pParse->db;

   /* Look up the table being altered. */

   assert( pParse->pNewTable==0 );

   assert( sqlite3BtreeHoldsAllMutexes(db) );

   if( db->mallocFailed ) goto exit_begin_add_column;

   pTab = sqlite3LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);

   if( !pTab ) goto exit_begin_add_column;

 #ifndef SQLITE_OMIT_VIRTUALTABLE

   if( IsVirtual(pTab) ){

     sqlite3ErrorMsg(pParse, "virtual tables may not be altered");

     goto exit_begin_add_column;

   }

 #endif

   /* Make sure this is not an attempt to ALTER a view. */

   if( pTab->pSelect ){

     sqlite3ErrorMsg(pParse, "Cannot add a column to a view");

     goto exit_begin_add_column;

   }

   assert( pTab->addColOffset>0 );

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

   /* Put a copy of the Table struct in Parse.pNewTable for the

   ** sqlite3AddColumn() function and friends to modify.

   */

   pNew = (Table*)sqlite3DbMallocZero(db, sizeof(Table));

   if( !pNew ) goto exit_begin_add_column;

   pParse->pNewTable = pNew;

   pNew->nRef = 1;

   pNew->db = db;

   pNew->nCol = pTab->nCol;

   assert( pNew->nCol>0 );

   nAlloc = (((pNew->nCol-1)/8)*8)+8;

   assert( nAlloc>=pNew->nCol && nAlloc%8==0 && nAlloc-pNew->nCol<8 );

   pNew->aCol = (Column*)sqlite3DbMallocZero(db, sizeof(Column)*nAlloc);

   pNew->zName = sqlite3DbStrDup(db, pTab->zName);

   if( !pNew->aCol || !pNew->zName ){

     db->mallocFailed = 1;

     goto exit_begin_add_column;

   }

   memcpy(pNew->aCol, pTab->aCol, sizeof(Column)*pNew->nCol);

   for(i=0; i<pNew->nCol; i++){

     Column *pCol = &pNew->aCol[i];

     pCol->zName = sqlite3DbStrDup(db, pCol->zName);

     pCol->zColl = 0;

     pCol->zType = 0;

     pCol->pDflt = 0;

   }

   pNew->pSchema = db->aDb[iDb].pSchema;

   pNew->addColOffset = pTab->addColOffset;

   pNew->nRef = 1;

   /* Begin a transaction and increment the schema cookie.  */

   sqlite3BeginWriteOperation(pParse, 0, iDb);

   v = sqlite3GetVdbe(pParse);

   if( !v ) goto exit_begin_add_column;

   sqlite3ChangeCookie(pParse, iDb);

 exit_begin_add_column:

   sqlite3SrcListDelete(db, pSrc);

   return;

 }

 #endif  /* SQLITE_ALTER_TABLE */