src/alter.c

/*
** 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.
*/
#include "sqliteInt.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 to create the text of expressions of the form:
**
**   name=<constant1> OR name=<constant2> OR ...
**
** If argument zWhere is NULL, then a pointer string containing the text 
** "name=<constant>" is returned, where <constant> is the quoted version
** of the string passed as argument zConstant. The returned buffer is
** allocated using sqlite3DbMalloc(). It is the responsibility of the
** caller to ensure that it is eventually freed.
**
** If argument zWhere is not NULL, then the string returned is 
** "<where> OR name=<constant>", where <where> is the contents of zWhere.
** In this case zWhere is passed to sqlite3DbFree() before returning.
** 
*/
static char *whereOrName(sqlite3 *db, char *zWhere, char *zConstant){
  char *zNew;
  if( !zWhere ){
    zNew = sqlite3MPrintf(db, "name=%Q", zConstant);
  }else{
    zNew = sqlite3MPrintf(db, "%s OR name=%Q", zWhere, zConstant);
    sqlite3DbFree(db, zWhere);
  }
  return zNew;
}

#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
/*
** Generate the text of a WHERE expression which can be used to select all
** tables that have foreign key constraints that refer to table pTab (i.e.
** constraints for which pTab is the parent table) from the sqlite_master
** table.
*/
static char *whereForeignKeys(Parse *pParse, Table *pTab){
  FKey *p;
  char *zWhere = 0;
  for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
    zWhere = whereOrName(pParse->db, zWhere, p->pFrom->zName);
  }
  return zWhere;
}
#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;
  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=sqlite3TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
      if( pTrig->pSchema==pTempSchema ){
        zWhere = whereOrName(db, zWhere, pTrig->zName);
      }
    }
  }
  if( zWhere ){
    char *zNew = sqlite3MPrintf(pParse->db, "type='trigger' AND (%s)", zWhere);
    sqlite3DbFree(pParse->db, zWhere);
    zWhere = zNew;
  }
  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( NEVER(v==0) ) 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=sqlite3TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
    int iTrigDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
    assert( iTrigDb==iDb || iTrigDb==1 );
    sqlite3VdbeAddOp4(v, OP_DropTrigger, iTrigDb, 0, 0, pTrig->zName, 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;
  sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere);

#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 ){
    sqlite3VdbeAddParseSchemaOp(v, 1, zWhere);
  }
#endif
}

/*
** Parameter zName is the name of a table that is about to be altered
** (either with ALTER TABLE ... RENAME TO or ALTER TABLE ... ADD COLUMN).
** If the table is a system table, this function leaves an error message
** in pParse->zErr (system tables may not be altered) and returns non-zero.
**
** Or, if zName is not a system table, zero is returned.
*/
static int isSystemTable(Parse *pParse, const char *zName){
  if( 0==sqlite3StrNICmp(zName, "sqlite_", 7) ){
    sqlite3ErrorMsg(pParse, "table %s may not be altered", zName);
    return 1;
  }
  return 0;
}

/*
** 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;
  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
  u32 savedDbFlags;         /* Saved value of db->mDbFlags */

  savedDbFlags = db->mDbFlags;  
  if( NEVER(db->mallocFailed) ) goto exit_rename_table;
  assert( pSrc->nSrc==1 );
  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );

  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
  if( !pTab ) goto exit_rename_table;
  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
  zDb = db->aDb[iDb].zDbSName;
  db->mDbFlags |= DBFLAG_PreferBuiltin;

  /* 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( SQLITE_OK!=isSystemTable(pParse, 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) ){
    pVTab = sqlite3GetVTable(db, pTab);
    if( pVTab->pVtab->pModule->xRename==0 ){
      pVTab = 0;
    }
  }
#endif

  /* Begin a transaction 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, pVTab!=0, 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( pVTab ){
    int i = ++pParse->nMem;
    sqlite3VdbeLoadString(v, i, zName);
    sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pVTab, P4_VTAB);
    sqlite3MayAbort(pParse);
  }
#endif

  /* figure out how many UTF-8 characters are in zName */
  zTabName = pTab->zName;
  nTabName = sqlite3Utf8CharLen(zTabName, -1);

  /* Rewrite all CREATE TABLE, INDEX, TRIGGER or VIEW statements in
  ** the schema to use the new table name.  */
  sqlite3NestedParse(pParse, 
      "UPDATE \"%w\".%s SET "
      "sql = sqlite_rename_table(%Q, sql, %Q, %Q, 0) "
      "WHERE (type!='index' OR tbl_name=%Q COLLATE nocase)"
      "AND   name NOT LIKE 'sqlite_%%'"
      , zDb, MASTER_NAME, zDb, zTabName, zName, zTabName
  );

  /* Update the tbl_name and name columns of the sqlite_master table
  ** as required.  */
  sqlite3NestedParse(pParse,
      "UPDATE %Q.%s SET "
          "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 COLLATE nocase AND "
          "(type='table' OR type='index' OR type='trigger');", 
      zDb, MASTER_NAME, 
      zName, zName, 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

  /* If the table being renamed is not itself part of the temp database,
  ** edit view and trigger definitions within the temp database 
  ** as required.  */
  if( iDb!=1 ){
    sqlite3NestedParse(pParse, 
        "UPDATE sqlite_temp_master SET "
            "sql = sqlite_rename_table(%Q, sql, %Q, %Q, 1), "
            "tbl_name = "
              "CASE WHEN tbl_name=%Q COLLATE nocase THEN %Q ELSE tbl_name END "
            "WHERE type IN ('view', 'trigger')"
        , zDb, zTabName, zName, zTabName, zTabName, zName);
  }

  sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iDb, 0);
  if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, 1, 0);

exit_rename_table:
  sqlite3SrcListDelete(db, pSrc);
  sqlite3DbFree(db, zName);
  db->mDbFlags = savedDbFlags;
}

/*
** 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; */
  Vdbe *v = pParse->pVdbe;  /* The prepared statement under construction */
  int r1;                   /* Temporary registers */

  db = pParse->db;
  if( pParse->nErr || db->mallocFailed ) return;
  assert( v!=0 );
  pNew = pParse->pNewTable;
  assert( pNew );

  assert( sqlite3BtreeHoldsAllMutexes(db) );
  iDb = sqlite3SchemaToIndex(db, pNew->pSchema);
  zDb = db->aDb[iDb].zDbSName;
  zTab = &pNew->zName[16];  /* Skip the "sqlite_altertab_" prefix on the name */
  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.
  */
  assert( pDflt==0 || pDflt->op==TK_SPAN );
  if( pDflt && pDflt->pLeft->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->colFlags & COLFLAG_PRIMKEY ){
    sqlite3ErrorMsg(pParse, "Cannot add a PRIMARY KEY column");
    return;
  }
  if( pNew->pIndex ){
    sqlite3ErrorMsg(pParse, "Cannot add a UNIQUE column");
    return;
  }
  if( (db->flags&SQLITE_ForeignKeys) && pNew->pFKey && pDflt ){
    sqlite3ErrorMsg(pParse, 
        "Cannot add a REFERENCES column with non-NULL default value");
    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 = 0;
    int rc;
    rc = sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_BLOB, &pVal);
    assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
    if( rc!=SQLITE_OK ){
      assert( 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];
    u32 savedDbFlags = db->mDbFlags;
    while( zEnd>zCol && (*zEnd==';' || sqlite3Isspace(*zEnd)) ){
      *zEnd-- = '\0';
    }
    db->mDbFlags |= DBFLAG_PreferBuiltin;
    sqlite3NestedParse(pParse, 
        "UPDATE \"%w\".%s SET "
          "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "
        "WHERE type = 'table' AND name = %Q", 
      zDb, MASTER_NAME, pNew->addColOffset, zCol, pNew->addColOffset+1,
      zTab
    );
    sqlite3DbFree(db, zCol);
    db->mDbFlags = savedDbFlags;
  }

  /* Make sure the schema version is at least 3.  But do not upgrade
  ** from less than 3 to 4, as that will corrupt any preexisting DESC
  ** index.
  */
  r1 = sqlite3GetTempReg(pParse);
  sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, r1, BTREE_FILE_FORMAT);
  sqlite3VdbeUsesBtree(v, iDb);
  sqlite3VdbeAddOp2(v, OP_AddImm, r1, -2);
  sqlite3VdbeAddOp2(v, OP_IfPos, r1, sqlite3VdbeCurrentAddr(v)+2);
  VdbeCoverage(v);
  sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, 3);
  sqlite3ReleaseTempReg(pParse, r1);

  /* 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 = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
  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;
  }
  if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ){
    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.  But modify
  ** the name by adding an "sqlite_altertab_" prefix.  By adding this
  ** prefix, we insure that the name will not collide with an existing
  ** table because user table are not allowed to have the "sqlite_"
  ** prefix on their name.
  */
  pNew = (Table*)sqlite3DbMallocZero(db, sizeof(Table));
  if( !pNew ) goto exit_begin_add_column;
  pParse->pNewTable = pNew;
  pNew->nTabRef = 1;
  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 = sqlite3MPrintf(db, "sqlite_altertab_%s", pTab->zName);
  if( !pNew->aCol || !pNew->zName ){
    assert( db->mallocFailed );
    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->pDflt = 0;
  }
  pNew->pSchema = db->aDb[iDb].pSchema;
  pNew->addColOffset = pTab->addColOffset;
  pNew->nTabRef = 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;
}

/*
** Parameter pTab is the subject of an ALTER TABLE ... RENAME COLUMN
** command. This function checks if the table is a view or virtual
** table (columns of views or virtual tables may not be renamed). If so,
** it loads an error message into pParse and returns non-zero.
**
** Or, if pTab is not a view or virtual table, zero is returned.
*/
#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
static int isRealTable(Parse *pParse, Table *pTab){
  const char *zType = 0;
#ifndef SQLITE_OMIT_VIEW
  if( pTab->pSelect ){
    zType = "view";
  }else 
#endif
#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( IsVirtual(pTab) ){
    zType = "virtual table";
  }
#endif
  if( zType ){
    sqlite3ErrorMsg(
        pParse, "cannot rename columns of %s \"%s\"", zType, pTab->zName
    );
    return 1;
  }
  return 0;
}
#else /* !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE) */
# define isRealTable(x,y) (0)
#endif

/*
** Handles the following parser reduction:
**
**  cmd ::= ALTER TABLE pSrc RENAME COLUMN pOld TO pNew
*/
void sqlite3AlterRenameColumn(
  Parse *pParse,                  /* Parsing context */
  SrcList *pSrc,                  /* Table being altered.  pSrc->nSrc==1 */
  Token *pOld,                    /* Name of column being changed */
  Token *pNew                     /* New column name */
){
  sqlite3 *db = pParse->db;       /* Database connection */
  Table *pTab;                    /* Table being updated */
  int iCol;                       /* Index of column being renamed */
  char *zOld = 0;                 /* Old column name */
  char *zNew = 0;                 /* New column name */
  const char *zDb;                /* Name of schema containing the table */
  int iSchema;                    /* Index of the schema */
  int bQuote;                     /* True to quote the new name */

  /* Locate the table to be altered */
  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
  if( !pTab ) goto exit_rename_column;

  /* Cannot alter a system table */
  if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ) goto exit_rename_column;
  if( SQLITE_OK!=isRealTable(pParse, pTab) ) goto exit_rename_column;

  /* Which schema holds the table to be altered */  
  iSchema = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iSchema>=0 );
  zDb = db->aDb[iSchema].zDbSName;

  /* Make sure the old name really is a column name in the table to be
  ** altered.  Set iCol to be the index of the column being renamed */
  zOld = sqlite3NameFromToken(db, pOld);
  if( !zOld ) goto exit_rename_column;
  for(iCol=0; iCol<pTab->nCol; iCol++){
    if( 0==sqlite3StrICmp(pTab->aCol[iCol].zName, zOld) ) break;
  }
  if( iCol==pTab->nCol ){
    sqlite3ErrorMsg(pParse, "no such column: \"%s\"", zOld);
    goto exit_rename_column;
  }

  /* Do the rename operation using a recursive UPDATE statement that
  ** uses the sqlite_rename_column() SQL function to compute the new
  ** CREATE statement text for the sqlite_master table.
  */
  zNew = sqlite3NameFromToken(db, pNew);
  if( !zNew ) goto exit_rename_column;
  assert( pNew->n>0 );
  bQuote = sqlite3Isquote(pNew->z[0]);
  sqlite3NestedParse(pParse, 
      "UPDATE \"%w\".%s SET "
      "sql = sqlite_rename_column(sql, type, name, %Q, %Q, %d, %Q, %d) "
      "WHERE name NOT LIKE 'sqlite_%%' AND (type != 'index' OR tbl_name = %Q)"
      " AND sql NOT LIKE 'create virtual%%'",
      zDb, MASTER_NAME, 
      zDb, pTab->zName, iCol, zNew, bQuote,
      pTab->zName
  );

  /* Drop and reload the database schema. */
  if( pParse->pVdbe ){
    sqlite3ChangeCookie(pParse, iSchema);
    sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iSchema, 0);
  }

  sqlite3NestedParse(pParse, 
      "SELECT 1 "
      "FROM \"%w\".%s "
      "WHERE name NOT LIKE 'sqlite_%%' AND (type != 'index' OR tbl_name = %Q)"
      " AND sql NOT LIKE 'create virtual%%'"
      " AND sqlite_rename_column(sql, type, name, %Q, %Q, %d, %Q, -1)=0 ",
      zDb, MASTER_NAME, 
      pTab->zName,
      zDb, pTab->zName, iCol, zNew
  );

 exit_rename_column:
  sqlite3SrcListDelete(db, pSrc);
  sqlite3DbFree(db, zOld);
  sqlite3DbFree(db, zNew);
  return;
}

/*
** Each RenameToken object maps an element of the parse tree into
** the token that generated that element.  The parse tree element
** might be one of:
**
**     *  A pointer to an Expr that represents an ID
**     *  The name of a table column in Column.zName
**
** A list of RenameToken objects can be constructed during parsing.
** Each new object is created by sqlite3RenameTokenMap().
** As the parse tree is transformed, the sqlite3RenameTokenRemap()
** routine is used to keep the mapping current.
**
** After the parse finishes, renameTokenFind() routine can be used
** to look up the actual token value that created some element in
** the parse tree.
*/
struct RenameToken {
  void *p;               /* Parse tree element created by token t */
  Token t;               /* The token that created parse tree element p */
  RenameToken *pNext;    /* Next is a list of all RenameToken objects */
};

/*
** The context of an ALTER TABLE RENAME COLUMN operation that gets passed
** down into the Walker.
*/
typedef struct RenameCtx RenameCtx;
struct RenameCtx {
  RenameToken *pList;             /* List of tokens to overwrite */
  int nList;                      /* Number of tokens in pList */
  int iCol;                       /* Index of column being renamed */
  Table *pTab;                    /* Table being ALTERed */ 
  const char *zOld;               /* Old column name */
};

void renameTokenClear(Parse *pParse, void *pPtr){
  RenameToken *p;
  assert( pPtr );
  for(p=pParse->pRename; p; p=p->pNext){
    if( p->p==pPtr ){
      p->p = 0;
    }
  }
}

/*
** Add a new RenameToken object mapping parse tree element pPtr into
** token *pToken to the Parse object currently under construction.
**
** Return a copy of pPtr.
*/
void *sqlite3RenameTokenMap(Parse *pParse, void *pPtr, Token *pToken){
  RenameToken *pNew;
  assert( pPtr || pParse->db->mallocFailed );

  renameTokenClear(pParse, pPtr);
  pNew = sqlite3DbMallocZero(pParse->db, sizeof(RenameToken));
  if( pNew ){
    pNew->p = pPtr;
    pNew->t = *pToken;
    pNew->pNext = pParse->pRename;
    pParse->pRename = pNew;
  }

  return pPtr;
}

/*
** It is assumed that there is already a RenameToken object associated
** with parse tree element pFrom. This function remaps the associated token
** to parse tree element pTo.
*/
void sqlite3RenameTokenRemap(Parse *pParse, void *pTo, void *pFrom){
  RenameToken *p;
  if( pTo ) renameTokenClear(pParse, pTo);
  for(p=pParse->pRename; p; p=p->pNext){
    if( p->p==pFrom ){
      p->p = pTo;
      break;
    }
  }
}

/*
** Free the list of RenameToken objects given in the second argument
*/
static void renameTokenFree(sqlite3 *db, RenameToken *pToken){
  RenameToken *pNext;
  RenameToken *p;
  for(p=pToken; p; p=pNext){
    pNext = p->pNext;
    sqlite3DbFree(db, p);
  }
}

/*
** Search the Parse object passed as the first argument for a RenameToken
** object associated with parse tree element pPtr. If found, remove it
** from the Parse object and add it to the list maintained by the
** RenameCtx object passed as the second argument.
*/
static void renameTokenFind(Parse *pParse, struct RenameCtx *pCtx, void *pPtr){
  RenameToken **pp;
  assert( pPtr!=0 );
  for(pp=&pParse->pRename; (*pp); pp=&(*pp)->pNext){
    if( (*pp)->p==pPtr ){
      RenameToken *pToken = *pp;
      *pp = pToken->pNext;
      pToken->pNext = pCtx->pList;
      pCtx->pList = pToken;
      pCtx->nList++;
      break;
    }
  }
}

/*
** This is a Walker select callback. It does nothing. It is only required
** because without a dummy callback, sqlite3WalkExpr() and similar do not
** descend into sub-select statements.
*/
static int renameColumnSelectCb(Walker *pWalker, Select *p){
  UNUSED_PARAMETER(pWalker);
  UNUSED_PARAMETER(p);
  return WRC_Continue;
}

/*
** This is a Walker expression callback.
**
** For every TK_COLUMN node in the expression tree, search to see
** if the column being references is the column being renamed by an
** ALTER TABLE statement.  If it is, then attach its associated
** RenameToken object to the list of RenameToken objects being
** constructed in RenameCtx object at pWalker->u.pRename.
*/
static int renameColumnExprCb(Walker *pWalker, Expr *pExpr){
  RenameCtx *p = pWalker->u.pRename;
  if( pExpr->op==TK_TRIGGER 
   && pExpr->iColumn==p->iCol 
   && pWalker->pParse->pTriggerTab==p->pTab
  ){
    renameTokenFind(pWalker->pParse, p, (void*)pExpr);
  }else if( pExpr->op==TK_COLUMN 
   && pExpr->iColumn==p->iCol 
   && p->pTab==pExpr->pTab
  ){
    renameTokenFind(pWalker->pParse, p, (void*)pExpr);
  }
  return WRC_Continue;
}

/*
** The RenameCtx contains a list of tokens that reference a column that
** is being renamed by an ALTER TABLE statement.  Return the "last"
** RenameToken in the RenameCtx and remove that RenameToken from the
** RenameContext.  "Last" means the last RenameToken encountered when
** the input SQL is parsed from left to right.  Repeated calls to this routine
** return all column name tokens in the order that they are encountered
** in the SQL statement.
*/
static RenameToken *renameColumnTokenNext(RenameCtx *pCtx){
  RenameToken *pBest = pCtx->pList;
  RenameToken *pToken;
  RenameToken **pp;

  for(pToken=pBest->pNext; pToken; pToken=pToken->pNext){
    if( pToken->t.z>pBest->t.z ) pBest = pToken;
  }
  for(pp=&pCtx->pList; *pp!=pBest; pp=&(*pp)->pNext);
  *pp = pBest->pNext;

  return pBest;
}

/*
** An error occured while parsing or otherwise processing a database
** object (either pParse->pNewTable, pNewIndex or pNewTrigger) as part of an
** ALTER TABLE RENAME COLUMN program. The error message emitted by the
** sub-routine is currently stored in pParse->zErrMsg. This function
** adds context to the error message and then stores it in pCtx.
*/
static void renameColumnParseError(
  sqlite3_context *pCtx, 
  int bPost,
  sqlite3_value *pType,
  sqlite3_value *pObject,
  Parse *pParse
){
  const char *zT = (const char*)sqlite3_value_text(pType);
  const char *zN = (const char*)sqlite3_value_text(pObject);
  char *zErr;

  zErr = sqlite3_mprintf("error in %s %s%s: %s", 
      zT, zN, (bPost ? " after rename" : ""),
      pParse->zErrMsg
  );
  sqlite3_result_error(pCtx, zErr, -1);
  sqlite3_free(zErr);
}

/*
** For each name in the the expression-list pEList (i.e. each
** pEList->a[i].zName) that matches the string in zOld, extract the 
** corresponding rename-token from Parse object pParse and add it
** to the RenameCtx pCtx.
*/
static void renameColumnElistNames(
  Parse *pParse, 
  RenameCtx *pCtx, 
  ExprList *pEList, 
  const char *zOld
){
  if( pEList ){
    int i;
    for(i=0; i<pEList->nExpr; i++){
      char *zName = pEList->a[i].zName;
      if( 0==sqlite3_stricmp(zName, zOld) ){
        renameTokenFind(pParse, pCtx, (void*)zName);
      }
    }
  }
}

/*
** For each name in the the id-list pIdList (i.e. each pIdList->a[i].zName) 
** that matches the string in zOld, extract the corresponding rename-token 
** from Parse object pParse and add it to the RenameCtx pCtx.
*/
static void renameColumnIdlistNames(
  Parse *pParse, 
  RenameCtx *pCtx, 
  IdList *pIdList, 
  const char *zOld
){
  if( pIdList ){
    int i;
    for(i=0; i<pIdList->nId; i++){
      char *zName = pIdList->a[i].zName;
      if( 0==sqlite3_stricmp(zName, zOld) ){
        renameTokenFind(pParse, pCtx, (void*)zName);
      }
    }
  }
}

static int renameParseSql(
  Parse *p, 
  const char *zDb, 
  int bTable, 
  sqlite3 *db, 
  const char *zSql,
  int bTemp
){
  int rc;
  char *zErr = 0;

  db->init.iDb = bTemp ? 1 : sqlite3FindDbName(db, zDb);

  /* Parse the SQL statement passed as the first argument. If no error
  ** occurs and the parse does not result in a new table, index or
  ** trigger object, the database must be corrupt. */
  memset(p, 0, sizeof(Parse));
  p->eParseMode = (bTable ? PARSE_MODE_RENAME_TABLE : PARSE_MODE_RENAME_COLUMN);
  p->db = db;
  p->nQueryLoop = 1;
  rc = sqlite3RunParser(p, zSql, &zErr);
  assert( p->zErrMsg==0 );
  assert( rc!=SQLITE_OK || zErr==0 );
  assert( (0!=p->pNewTable) + (0!=p->pNewIndex) + (0!=p->pNewTrigger)<2 );
  p->zErrMsg = zErr;
  if( db->mallocFailed ) rc = SQLITE_NOMEM;
  if( rc==SQLITE_OK 
   && p->pNewTable==0 && p->pNewIndex==0 && p->pNewTrigger==0 
  ){
    rc = SQLITE_CORRUPT_BKPT;
  }

#ifdef SQLITE_DEBUG
  /* Ensure that all mappings in the Parse.pRename list really do map to
  ** a part of the input string.  */
  if( rc==SQLITE_OK ){
    int nSql = sqlite3Strlen30(zSql);
    RenameToken *pToken;
    for(pToken=p->pRename; pToken; pToken=pToken->pNext){
      assert( pToken->t.z>=zSql && &pToken->t.z[pToken->t.n]<=&zSql[nSql] );
    }
  }
#endif

  db->init.iDb = 0;
  return rc;
}

static int renameEditSql(
  sqlite3_context *pCtx,          /* Return result here */
  RenameCtx *pRename,             /* Rename context */
  const char *zSql,               /* SQL statement to edit */
  const char *zNew,               /* New token text */
  int bQuote                      /* True to always quote token */
){
  int nNew = sqlite3Strlen30(zNew);
  int nSql = sqlite3Strlen30(zSql);
  sqlite3 *db = sqlite3_context_db_handle(pCtx);
  int rc = SQLITE_OK;
  char *zQuot;
  char *zOut;
  int nQuot;

  /* Set zQuot to point to a buffer containing a quoted copy of the 
  ** identifier zNew. If the corresponding identifier in the original 
  ** ALTER TABLE statement was quoted (bQuote==1), then set zNew to
  ** point to zQuot so that all substitutions are made using the
  ** quoted version of the new column name.  */
  zQuot = sqlite3_mprintf("\"%w\"", zNew);
  if( zQuot==0 ){
    return SQLITE_NOMEM;
  }else{
    nQuot = sqlite3Strlen30(zQuot);
  }
  if( bQuote ){
    zNew = zQuot;
    nNew = nQuot;
  }

  /* At this point pRename->pList contains a list of RenameToken objects
  ** corresponding to all tokens in the input SQL that must be replaced
  ** with the new column name. All that remains is to construct and
  ** return the edited SQL string. */
  assert( nQuot>=nNew );
  zOut = sqlite3DbMallocZero(db, nSql + pRename->nList*nQuot + 1);
  if( zOut ){
    int nOut = nSql;
    memcpy(zOut, zSql, nSql);
    while( pRename->pList ){
      int iOff;                   /* Offset of token to replace in zOut */
      RenameToken *pBest = renameColumnTokenNext(pRename);

      u32 nReplace;
      const char *zReplace;
      if( sqlite3IsIdChar(*pBest->t.z) ){
        nReplace = nNew;
        zReplace = zNew;
      }else{
        nReplace = nQuot;
        zReplace = zQuot;
      }

      iOff = pBest->t.z - zSql;
      if( pBest->t.n!=nReplace ){
        memmove(&zOut[iOff + nReplace], &zOut[iOff + pBest->t.n], 
            nOut - (iOff + pBest->t.n)
        );
        nOut += nReplace - pBest->t.n;
        zOut[nOut] = '\0';
      }
      memcpy(&zOut[iOff], zReplace, nReplace);
      sqlite3DbFree(db, pBest);
    }

    sqlite3_result_text(pCtx, zOut, -1, SQLITE_TRANSIENT);
    sqlite3DbFree(db, zOut);
  }else{
    rc = SQLITE_NOMEM;
  }

  sqlite3_free(zQuot);
  return rc;
}

static int renameResolveTrigger(
  Parse *pParse,
  const char *zDb
){
  sqlite3 *db = pParse->db;
  TriggerStep *pStep;
  NameContext sNC;
  int rc = SQLITE_OK;

  memset(&sNC, 0, sizeof(sNC));
  sNC.pParse = pParse;
  pParse->pTriggerTab = sqlite3FindTable(db, pParse->pNewTrigger->table, zDb);
  pParse->eTriggerOp = pParse->pNewTrigger->op;

  /* Resolve symbols in WHEN clause */
  if( pParse->pNewTrigger->pWhen ){
    rc = sqlite3ResolveExprNames(&sNC, pParse->pNewTrigger->pWhen);
  }

  for(pStep=pParse->pNewTrigger->step_list; 
      rc==SQLITE_OK && pStep; 
      pStep=pStep->pNext
  ){
    if( pStep->pSelect ){
      sqlite3SelectPrep(pParse, pStep->pSelect, &sNC);
      if( pParse->nErr ) rc = pParse->rc;
    }
    if( rc==SQLITE_OK && pStep->zTarget ){ 
      Table *pTarget = sqlite3LocateTable(pParse, 0, pStep->zTarget, zDb);
      if( pTarget==0 ){
        rc = SQLITE_ERROR;
      }else{
        SrcList sSrc;
        memset(&sSrc, 0, sizeof(sSrc));
        sSrc.nSrc = 1;
        sSrc.a[0].zName = pStep->zTarget;
        sSrc.a[0].pTab = pTarget;
        sNC.pSrcList = &sSrc;
        if( pStep->pWhere ){
          rc = sqlite3ResolveExprNames(&sNC, pStep->pWhere);
        }
        if( rc==SQLITE_OK ){
          rc = sqlite3ResolveExprListNames(&sNC, pStep->pExprList);
        }
        assert( !pStep->pUpsert || (!pStep->pWhere && !pStep->pExprList) );
        if( pStep->pUpsert ){
          Upsert *pUpsert = pStep->pUpsert;
          assert( rc==SQLITE_OK );
          pUpsert->pUpsertSrc = &sSrc;
          sNC.uNC.pUpsert = pUpsert;
          sNC.ncFlags = NC_UUpsert;
          rc = sqlite3ResolveExprListNames(&sNC, pUpsert->pUpsertTarget);
          if( rc==SQLITE_OK ){
            ExprList *pUpsertSet = pUpsert->pUpsertSet;
            rc = sqlite3ResolveExprListNames(&sNC, pUpsertSet);
          }
          if( rc==SQLITE_OK ){
            rc = sqlite3ResolveExprNames(&sNC, pUpsert->pUpsertWhere);
          }
          if( rc==SQLITE_OK ){
            rc = sqlite3ResolveExprNames(&sNC, pUpsert->pUpsertTargetWhere);
          }
          sNC.ncFlags = 0;
        }
      }
    }
  }
  return rc;
}

static void renameWalkTrigger(Walker *pWalker, Trigger *pTrigger){
  TriggerStep *pStep;

  /* Find tokens to edit in WHEN clause */
  sqlite3WalkExpr(pWalker, pTrigger->pWhen);

  /* Find tokens to edit in trigger steps */
  for(pStep=pTrigger->step_list; pStep; pStep=pStep->pNext){
    sqlite3WalkSelect(pWalker, pStep->pSelect);
    sqlite3WalkExpr(pWalker, pStep->pWhere);
    sqlite3WalkExprList(pWalker, pStep->pExprList);
    if( pStep->pUpsert ){
      Upsert *pUpsert = pStep->pUpsert;
      sqlite3WalkExprList(pWalker, pUpsert->pUpsertTarget);
      sqlite3WalkExprList(pWalker, pUpsert->pUpsertSet);
      sqlite3WalkExpr(pWalker, pUpsert->pUpsertWhere);
      sqlite3WalkExpr(pWalker, pUpsert->pUpsertTargetWhere);
    }
  }
}

/*
** SQL function:
**
**     sqlite_rename_column(zSql, iCol, bQuote, zNew, zTable, zOld)
**
**   0. zSql:     SQL statement to rewrite
**   1. type:     Type of object ("table", "view" etc.)
**   2. object:   Name of object
**   3. Database: Database name (e.g. "main")
**   4. Table:    Table name
**   5. iCol:     Index of column to rename
**   6. zNew:     New column name
**   7. bQuote:   Non-zero if the new column name should be quoted. Negative
**                if this function is being called to check that the schema
**                can still be parsed and symbols resolved after the column
**                has been renamed.
**
** Do a column rename operation on the CREATE statement given in zSql.
** The iCol-th column (left-most is 0) of table zTable is renamed from zCol
** into zNew.  The name should be quoted if bQuote is true.
**
** This function is used internally by the ALTER TABLE RENAME COLUMN command.
** Though accessible to application code, it is not intended for use by
** applications.  The existance of this function, and the way it works,
** is subject to change without notice.
**
** If any of the parameters are out-of-bounds, then simply return NULL.
** An out-of-bounds parameter can only occur when the application calls
** this function directly.  The parameters will always be well-formed when
** this routine is invoked by the bytecode for a legitimate ALTER TABLE
** statement.
*/
static void renameColumnFunc(
  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  RenameCtx sCtx;
  const char *zSql = (const char*)sqlite3_value_text(argv[0]);
  int nSql = sqlite3_value_bytes(argv[0]);
  const char *zDb = (const char*)sqlite3_value_text(argv[3]);
  const char *zTable = (const char*)sqlite3_value_text(argv[4]);
  int iCol = sqlite3_value_int(argv[5]);
  const char *zNew = (const char*)sqlite3_value_text(argv[6]);
  int nNew = sqlite3_value_bytes(argv[6]);
  int bQuote = sqlite3_value_int(argv[7]);
  const char *zOld;
  int bTemp = 0;

  int rc;
  char *zErr = 0;
  Parse sParse;
  Walker sWalker;
  Index *pIdx;
  char *zOut = 0;

  int i;
  Table *pTab;

  UNUSED_PARAMETER(NotUsed);
  if( zSql==0 ) return;
  if( zTable==0 ) return;
  if( zNew==0 ) return;
  if( iCol<0 ) return;
  sqlite3BtreeEnterAll(db);
  pTab = sqlite3FindTable(db, zTable, zDb);
  if( pTab==0 || iCol>=pTab->nCol ){
    sqlite3BtreeLeaveAll(db);
    return;
  }
  zOld = pTab->aCol[iCol].zName;
  memset(&sCtx, 0, sizeof(sCtx));
  sCtx.iCol = ((iCol==pTab->iPKey) ? -1 : iCol);

  rc = renameParseSql(&sParse, zDb, 0, db, zSql, bTemp);

  /* Find tokens that need to be replaced. */
  memset(&sWalker, 0, sizeof(Walker));
  sWalker.pParse = &sParse;
  sWalker.xExprCallback = renameColumnExprCb;
  sWalker.xSelectCallback = renameColumnSelectCb;
  sWalker.u.pRename = &sCtx;

  sCtx.pTab = pTab;
  if( rc!=SQLITE_OK ) goto renameColumnFunc_done;
  if( sParse.pNewTable ){
    Select *pSelect = sParse.pNewTable->pSelect;
    if( pSelect ){
      sParse.rc = SQLITE_OK;
      sqlite3SelectPrep(&sParse, sParse.pNewTable->pSelect, 0);
      rc = (db->mallocFailed ? SQLITE_NOMEM : sParse.rc);
      if( rc==SQLITE_OK ){
        sqlite3WalkSelect(&sWalker, pSelect);
      }
      if( rc!=SQLITE_OK ) goto renameColumnFunc_done;
    }else{
      /* A regular table */
      int bFKOnly = sqlite3_stricmp(zTable, sParse.pNewTable->zName);
      FKey *pFKey;
      assert( sParse.pNewTable->pSelect==0 );
      sCtx.pTab = sParse.pNewTable;
      if( bFKOnly==0 ){
        renameTokenFind(
            &sParse, &sCtx, (void*)sParse.pNewTable->aCol[iCol].zName
        );
        if( sCtx.iCol<0 ){
          renameTokenFind(&sParse, &sCtx, (void*)&sParse.pNewTable->iPKey);
        }
        sqlite3WalkExprList(&sWalker, sParse.pNewTable->pCheck);
        for(pIdx=sParse.pNewTable->pIndex; pIdx; pIdx=pIdx->pNext){
          sqlite3WalkExprList(&sWalker, pIdx->aColExpr);
        }
      }

      for(pFKey=sParse.pNewTable->pFKey; pFKey; pFKey=pFKey->pNextFrom){
        for(i=0; i<pFKey->nCol; i++){
          if( bFKOnly==0 && pFKey->aCol[i].iFrom==iCol ){
            renameTokenFind(&sParse, &sCtx, (void*)&pFKey->aCol[i]);
          }
          if( 0==sqlite3_stricmp(pFKey->zTo, zTable)
           && 0==sqlite3_stricmp(pFKey->aCol[i].zCol, zOld)
          ){
            renameTokenFind(&sParse, &sCtx, (void*)pFKey->aCol[i].zCol);
          }
        }
      }
    }
  }else if( sParse.pNewIndex ){
    sqlite3WalkExprList(&sWalker, sParse.pNewIndex->aColExpr);
    sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
  }else{
    /* A trigger */
    TriggerStep *pStep;
    rc = renameResolveTrigger(&sParse, zDb);
    if( rc!=SQLITE_OK ) goto renameColumnFunc_done;

    for(pStep=sParse.pNewTrigger->step_list; pStep; pStep=pStep->pNext){
      if( pStep->zTarget ){ 
        Table *pTarget = sqlite3LocateTable(&sParse, 0, pStep->zTarget, zDb);
        if( pTarget==pTab ){
          if( pStep->pUpsert ){
            ExprList *pUpsertSet = pStep->pUpsert->pUpsertSet;
            renameColumnElistNames(&sParse, &sCtx, pUpsertSet, zOld);
          }
          renameColumnIdlistNames(&sParse, &sCtx, pStep->pIdList, zOld);
          renameColumnElistNames(&sParse, &sCtx, pStep->pExprList, zOld);
        }
      }
    }


    /* Find tokens to edit in UPDATE OF clause */
    if( sParse.pTriggerTab==pTab ){
      renameColumnIdlistNames(&sParse, &sCtx,sParse.pNewTrigger->pColumns,zOld);
    }

    /* Find tokens to edit in various expressions and selects */
    renameWalkTrigger(&sWalker, sParse.pNewTrigger);
  }

  assert( rc==SQLITE_OK );
  rc = renameEditSql(context, &sCtx, zSql, zNew, bQuote);

renameColumnFunc_done:
  if( rc!=SQLITE_OK ){
    if( sParse.zErrMsg ){
      renameColumnParseError(context, (bQuote<0), argv[1], argv[2], &sParse);
    }else{
      sqlite3_result_error_code(context, rc);
    }
  }

  if( sParse.pVdbe ){
    sqlite3VdbeFinalize(sParse.pVdbe);
  }
  sqlite3DeleteTable(db, sParse.pNewTable);
  if( sParse.pNewIndex ) sqlite3FreeIndex(db, sParse.pNewIndex);
  sqlite3DeleteTrigger(db, sParse.pNewTrigger);
  renameTokenFree(db, sParse.pRename);
  renameTokenFree(db, sCtx.pList);
  sqlite3DbFree(db, sParse.zErrMsg);
  sqlite3ParserReset(&sParse);
  sqlite3BtreeLeaveAll(db);
}

static int renameTableExprCb(Walker *pWalker, Expr *pExpr){
  RenameCtx *p = pWalker->u.pRename;
  if( pExpr->op==TK_COLUMN && p->pTab==pExpr->pTab ){
    renameTokenFind(pWalker->pParse, p, (void*)&pExpr->pTab);
  }
  return WRC_Continue;
}

/*
** This is a Walker select callback. 
*/
static int renameTableSelectCb(Walker *pWalker, Select *pSelect){
  int i;
  RenameCtx *p = pWalker->u.pRename;
  SrcList *pSrc = pSelect->pSrc;
  for(i=0; i<pSrc->nSrc; i++){
    struct SrcList_item *pItem = &pSrc->a[i];
    if( pItem->pTab==p->pTab ){
      renameTokenFind(pWalker->pParse, p, pItem->zName);
    }
  }

  return WRC_Continue;
}


/*
** This C function implements an SQL user function that is used by SQL code
** generated by the ALTER TABLE ... RENAME command to modify the definition
** of any foreign key constraints that use the table being renamed as the 
** parent table. It is passed three arguments:
**
**   1) The complete text of the CREATE TABLE statement being modified,
**   2) The old name of the table being renamed, and
**   3) The new name of the table being renamed.
**
** It returns the new CREATE TABLE statement. For example:
**
**   sqlite_rename_table('CREATE TABLE t1(a REFERENCES t2)', 't2', 't3')
**       -> 'CREATE TABLE t1(a REFERENCES t3)'
*/
static void renameTableFunc(
  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  char *zOutput = 0;
  char *zResult;
  unsigned char const *zDb = sqlite3_value_text(argv[0]);
  unsigned char const *zInput = sqlite3_value_text(argv[1]);
  unsigned char const *zOld = sqlite3_value_text(argv[2]);
  unsigned char const *zNew = sqlite3_value_text(argv[3]);
  int bTemp = sqlite3_value_int(argv[4]);

  unsigned const char *z;         /* Pointer to token */
  int n;                          /* Length of token z */
  int token;                      /* Type of token */

  Parse sParse;
  int rc;
  int bQuote = 1;
  RenameCtx sCtx;
  Walker sWalker;

  if( zInput==0 || zOld==0 || zNew==0 ) return;

  memset(&sCtx, 0, sizeof(RenameCtx));
  sCtx.pTab = sqlite3FindTable(db, zOld, zDb);
  memset(&sWalker, 0, sizeof(Walker));
  sWalker.pParse = &sParse;
  sWalker.xExprCallback = renameTableExprCb;
  sWalker.xSelectCallback = renameTableSelectCb;
  sWalker.u.pRename = &sCtx;

  sqlite3BtreeEnterAll(db);

  rc = renameParseSql(&sParse, zDb, 1, db, zInput, bTemp);

  if( rc==SQLITE_OK ){
    if( sParse.pNewTable ){
      Table *pTab = sParse.pNewTable;

      if( pTab->pSelect ){
        NameContext sNC;
        memset(&sNC, 0, sizeof(sNC));
        sNC.pParse = &sParse;

        sqlite3SelectPrep(&sParse, pTab->pSelect, &sNC);
        if( sParse.nErr ) rc = sParse.rc;
        sqlite3WalkSelect(&sWalker, pTab->pSelect);
      }else{
        /* Modify any FK definitions to point to the new table. */
#ifndef SQLITE_OMIT_FOREIGN_KEY
        FKey *pFKey;
        for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){
          if( sqlite3_stricmp(pFKey->zTo, zOld)==0 ){
            renameTokenFind(&sParse, &sCtx, (void*)pFKey->zTo);
          }
        }
#endif

        /* If this is the table being altered, fix any table refs in CHECK
        ** expressions. Also update the name that appears right after the
        ** "CREATE [VIRTUAL] TABLE" bit. */
        if( sqlite3_stricmp(zOld, pTab->zName)==0 ){
          sCtx.pTab = pTab;
          sqlite3WalkExprList(&sWalker, pTab->pCheck);
          renameTokenFind(&sParse, &sCtx, pTab->zName);
        }
      }
    }

    else if( sParse.pNewIndex ){
      renameTokenFind(&sParse, &sCtx, sParse.pNewIndex->zName);
      sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
    }

#ifndef SQLITE_OMIT_TRIGGER
    else if( sParse.pNewTrigger ){
      Trigger *pTrigger = sParse.pNewTrigger;
      TriggerStep *pStep;
      if( 0==sqlite3_stricmp(sParse.pNewTrigger->table, zOld) 
       && sCtx.pTab->pSchema==pTrigger->pTabSchema
      ){
        renameTokenFind(&sParse, &sCtx, sParse.pNewTrigger->table);
      }

      rc = renameResolveTrigger(&sParse, zDb);
      if( rc==SQLITE_OK ){
        renameWalkTrigger(&sWalker, pTrigger);
      }

      for(pStep=pTrigger->step_list; pStep; pStep=pStep->pNext){
        if( pStep->zTarget && 0==sqlite3_stricmp(pStep->zTarget, zOld) ){
          renameTokenFind(&sParse, &sCtx, pStep->zTarget);
        }
      }
    }
#endif
  }

  if( rc==SQLITE_OK ){
    rc = renameEditSql(context, &sCtx, zInput, zNew, bQuote);
  }

  if( rc!=SQLITE_OK ){
    sqlite3_result_error_code(context, rc);
  }
  if( sParse.pVdbe ){
    sqlite3VdbeFinalize(sParse.pVdbe);
  }
  sqlite3DeleteTable(db, sParse.pNewTable);
  if( sParse.pNewIndex ) sqlite3FreeIndex(db, sParse.pNewIndex);
  sqlite3DeleteTrigger(db, sParse.pNewTrigger);
  renameTokenFree(db, sParse.pRename);
  renameTokenFree(db, sCtx.pList);
  sqlite3DbFree(db, sParse.zErrMsg);
  sqlite3ParserReset(&sParse);
  sqlite3BtreeLeaveAll(db);

  return;
}

/*
** Register built-in functions used to help implement ALTER TABLE
*/
void sqlite3AlterFunctions(void){
  static FuncDef aAlterTableFuncs[] = {
    FUNCTION(sqlite_rename_column,  8, 0, 0, renameColumnFunc),
    FUNCTION(sqlite_rename_table,  5, 0, 0, renameTableFunc),
  };
  sqlite3InsertBuiltinFuncs(aAlterTableFuncs, ArraySize(aAlterTableFuncs));
}
#endif  /* SQLITE_ALTER_TABLE */