/* 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. 
................................................................................
  pParse->pTriggerTab = sqlite3FindTable(db, pNew->table, 
      db->aDb[sqlite3SchemaToIndex2(db, pNew->pTabSchema, 0)].zDbSName
  );
  pParse->eTriggerOp = pNew->op;
  /* ALWAYS() because if the table of the trigger does not exist, the
  ** error would have been hit before this point */
  if( ALWAYS(pParse->pTriggerTab) ){

    rc = sqlite3ViewGetColumnNames(pParse, pParse->pTriggerTab);
  }

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

................................................................................
      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 if( SQLITE_OK==(rc = sqlite3ViewGetColumnNames(pParse, pTarget)) ){
        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;
}

  /* 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, iDb, pTab) ){
    goto exit_rename_table;
  }
  if( IsVirtual(pTab) ){
    pVTab = sqlite3GetVTable(db, -1, pTab);
    if( pVTab->pVtab->pModule->xRename==0 ){
      pVTab = 0;
    }
  }
#endif

  /* Begin a transaction for database iDb. 
................................................................................
  pParse->pTriggerTab = sqlite3FindTable(db, pNew->table, 
      db->aDb[sqlite3SchemaToIndex2(db, pNew->pTabSchema, 0)].zDbSName
  );
  pParse->eTriggerOp = pNew->op;
  /* ALWAYS() because if the table of the trigger does not exist, the
  ** error would have been hit before this point */
  if( ALWAYS(pParse->pTriggerTab) ){
    int iDb = sqlite3SchemaToIndex2(db, pParse->pTriggerTab->pSchema, 0);
    rc = sqlite3ViewGetColumnNames(pParse, iDb, pParse->pTriggerTab);
  }

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

................................................................................
      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{
        int iDb = sqlite3SchemaToIndex2(db, pTarget->pSchema, 0);
        if( SQLITE_OK==(rc = sqlite3ViewGetColumnNames(pParse, iDb, pTarget)) ){
          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;
}

        );
        if( db->init.busy==0 ) sqlite3VdbeChangeP5(v, 1);
        VdbeComment((v,
              "usesStmtJournal=%d", pParse->mayAbort && pParse->isMultiWrite));
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
      for(i=0; i<pParse->nVtabLock; i++){
        char *vtab = (char *)sqlite3GetVTable(db, pParse->apVtabLock[i]);
        sqlite3VdbeAddOp4(v, OP_VBegin, 0, 0, 0, vtab, P4_VTAB);
      }
      pParse->nVtabLock = 0;
#endif

      /* Once all the cookies have been verified and transactions opened, 
      ** obtain the required table-locks. This is a no-op unless the 
................................................................................

#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
/*
** The Table structure pTable is really a VIEW.  Fill in the names of
** the columns of the view in the pTable structure.  Return the number
** of errors.  If an error is seen leave an error message in pParse->zErrMsg.
*/
int sqlite3ViewGetColumnNames(Parse *pParse, Table *pTable){
  Table *pSelTab;   /* A fake table from which we get the result set */
  Select *pSel;     /* Copy of the SELECT that implements the view */
  int nErr = 0;     /* Number of errors encountered */
  int n;            /* Temporarily holds the number of cursors assigned */
  sqlite3 *db = pParse->db;  /* Database connection for malloc errors */
#ifndef SQLITE_OMIT_VIRTUALTABLE
  int rc;
................................................................................
  sqlite3_xauth xAuth;       /* Saved xAuth pointer */
#endif

  assert( pTable );

#ifndef SQLITE_OMIT_VIRTUALTABLE
  db->nSchemaLock++;
  rc = sqlite3VtabCallConnect(pParse, pTable);
  db->nSchemaLock--;
  if( rc ){
    return 1;
  }
  if( IsVirtual(pTable) ) return 0;
#endif

................................................................................
  iDb = sqlite3SchemaToIndex2(db, pTab->pSchema, 0);
  assert( iDb>=0 && iDb<db->nDb );
  sqlite3SchemaWritable(pParse, iDb);

  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
  ** it is initialized.
  */
  if( IsVirtual(pTab) && sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto exit_drop_table;
  }
#ifndef SQLITE_OMIT_AUTHORIZATION
  {
    int code;
    const char *zTab = SCHEMA_TABLE(iDb);
    const char *zDb = db->aDb[iDb].zDbSName;
................................................................................
        code = SQLITE_DROP_TEMP_VIEW;
      }else{
        code = SQLITE_DROP_VIEW;
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    }else if( IsVirtual(pTab) ){
      code = SQLITE_DROP_VTABLE;
      zArg2 = sqlite3GetVTable(db, pTab)->pMod->zName;
#endif
    }else{
      if( !OMIT_TEMPDB && iDb==1 ){
        code = SQLITE_DROP_TEMP_TABLE;
      }else{
        code = SQLITE_DROP_TABLE;
      }

        );
        if( db->init.busy==0 ) sqlite3VdbeChangeP5(v, 1);
        VdbeComment((v,
              "usesStmtJournal=%d", pParse->mayAbort && pParse->isMultiWrite));
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
      for(i=0; i<pParse->nVtabLock; i++){
        char *vtab = (char *)pParse->apVtabLock[i];
        sqlite3VdbeAddOp4(v, OP_VBegin, 0, 0, 0, vtab, P4_VTAB);
      }
      pParse->nVtabLock = 0;
#endif

      /* Once all the cookies have been verified and transactions opened, 
      ** obtain the required table-locks. This is a no-op unless the 
................................................................................

#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
/*
** The Table structure pTable is really a VIEW.  Fill in the names of
** the columns of the view in the pTable structure.  Return the number
** of errors.  If an error is seen leave an error message in pParse->zErrMsg.
*/
int sqlite3ViewGetColumnNames(Parse *pParse, int iDb, Table *pTable){
  Table *pSelTab;   /* A fake table from which we get the result set */
  Select *pSel;     /* Copy of the SELECT that implements the view */
  int nErr = 0;     /* Number of errors encountered */
  int n;            /* Temporarily holds the number of cursors assigned */
  sqlite3 *db = pParse->db;  /* Database connection for malloc errors */
#ifndef SQLITE_OMIT_VIRTUALTABLE
  int rc;
................................................................................
  sqlite3_xauth xAuth;       /* Saved xAuth pointer */
#endif

  assert( pTable );

#ifndef SQLITE_OMIT_VIRTUALTABLE
  db->nSchemaLock++;
  rc = sqlite3VtabCallConnect(pParse, iDb, pTable);
  db->nSchemaLock--;
  if( rc ){
    return 1;
  }
  if( IsVirtual(pTable) ) return 0;
#endif

................................................................................
  iDb = sqlite3SchemaToIndex2(db, pTab->pSchema, 0);
  assert( iDb>=0 && iDb<db->nDb );
  sqlite3SchemaWritable(pParse, iDb);

  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
  ** it is initialized.
  */
  if( IsVirtual(pTab) && sqlite3ViewGetColumnNames(pParse, iDb, pTab) ){
    goto exit_drop_table;
  }
#ifndef SQLITE_OMIT_AUTHORIZATION
  {
    int code;
    const char *zTab = SCHEMA_TABLE(iDb);
    const char *zDb = db->aDb[iDb].zDbSName;
................................................................................
        code = SQLITE_DROP_TEMP_VIEW;
      }else{
        code = SQLITE_DROP_VIEW;
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    }else if( IsVirtual(pTab) ){
      code = SQLITE_DROP_VTABLE;
      zArg2 = sqlite3GetVTable(db, -1, pTab)->pMod->zName;
#endif
    }else{
      if( !OMIT_TEMPDB && iDb==1 ){
        code = SQLITE_DROP_TEMP_TABLE;
      }else{
        code = SQLITE_DROP_TABLE;
      }

**   3) The table is a shadow table, the database connection is in
**      defensive mode, and the current sqlite3_prepare()
**      is for a top-level SQL statement.
*/
static int tabIsReadOnly(Parse *pParse, Table *pTab){
  sqlite3 *db;
  if( IsVirtual(pTab) ){
    return sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0;
  }
  if( (pTab->tabFlags & (TF_Readonly|TF_Shadow))==0 ) return 0;
  db = pParse->db;
  if( (pTab->tabFlags & TF_Readonly)!=0 ){
    return sqlite3WritableSchema(db)==0 && pParse->nested==0;
  }
  assert( pTab->tabFlags & TF_Shadow );
................................................................................
    pWhere = sqlite3LimitWhere(
        pParse, pTabList, pWhere, pOrderBy, pLimit, "DELETE"
    );
    pOrderBy = 0;
    pLimit = 0;
  }
#endif




  /* If pTab is really a view, make sure it has been initialized.
  */
  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto delete_from_cleanup;
  }

  if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
    goto delete_from_cleanup;
  }
  iDb = sqlite3SchemaToIndex2(db, pTab->pSchema, pTabList->a[0].zDatabase);
  assert( iDb<db->nDb );
  rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, 
                            db->aDb[iDb].zDbSName);
  assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
  if( rcauth==SQLITE_DENY ){
    goto delete_from_cleanup;
  }
  assert(!isView || pTrigger);
................................................................................
      VdbeCoverage(v);
      assert( nKey==1 );
    }  
  
    /* Delete the row */
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( IsVirtual(pTab) ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
      sqlite3VtabMakeWritable(pParse, pTab);
      assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
      sqlite3MayAbort(pParse);
      if( eOnePass==ONEPASS_SINGLE ){
        sqlite3VdbeAddOp1(v, OP_Close, iTabCur);
        if( sqlite3IsToplevel(pParse) ){
          pParse->isMultiWrite = 0;
        }

**   3) The table is a shadow table, the database connection is in
**      defensive mode, and the current sqlite3_prepare()
**      is for a top-level SQL statement.
*/
static int tabIsReadOnly(Parse *pParse, Table *pTab){
  sqlite3 *db;
  if( IsVirtual(pTab) ){
    return sqlite3GetVTable(pParse->db, -1, pTab)->pMod->pModule->xUpdate==0;
  }
  if( (pTab->tabFlags & (TF_Readonly|TF_Shadow))==0 ) return 0;
  db = pParse->db;
  if( (pTab->tabFlags & TF_Readonly)!=0 ){
    return sqlite3WritableSchema(db)==0 && pParse->nested==0;
  }
  assert( pTab->tabFlags & TF_Shadow );
................................................................................
    pWhere = sqlite3LimitWhere(
        pParse, pTabList, pWhere, pOrderBy, pLimit, "DELETE"
    );
    pOrderBy = 0;
    pLimit = 0;
  }
#endif

  iDb = sqlite3SchemaToIndex2(db, pTab->pSchema, pTabList->a[0].zDatabase);
  assert( iDb<db->nDb );

  /* If pTab is really a view, make sure it has been initialized.
  */
  if( sqlite3ViewGetColumnNames(pParse, iDb, pTab) ){
    goto delete_from_cleanup;
  }

  if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
    goto delete_from_cleanup;
  }


  rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, 
                            db->aDb[iDb].zDbSName);
  assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
  if( rcauth==SQLITE_DENY ){
    goto delete_from_cleanup;
  }
  assert(!isView || pTrigger);
................................................................................
      VdbeCoverage(v);
      assert( nKey==1 );
    }  
  
    /* Delete the row */
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( IsVirtual(pTab) ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, iDb, pTab);
      sqlite3VtabMakeWritable(pParse, iDb, pTab);
      assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
      sqlite3MayAbort(pParse);
      if( eOnePass==ONEPASS_SINGLE ){
        sqlite3VdbeAddOp1(v, OP_Close, iTabCur);
        if( sqlite3IsToplevel(pParse) ){
          pParse->isMultiWrite = 0;
        }

** run without using a temporary table for the results of the SELECT. 
*/
static int readsTable(Parse *p, int iDb, Table *pTab){
  Vdbe *v = sqlite3GetVdbe(p);
  int i;
  int iEnd = sqlite3VdbeCurrentAddr(v);
#ifndef SQLITE_OMIT_VIRTUALTABLE
  VTable *pVTab = IsVirtual(pTab) ? sqlite3GetVTable(p->db, pTab) : 0;
#endif

  for(i=1; i<iEnd; i++){
    VdbeOp *pOp = sqlite3VdbeGetOp(v, i);
    assert( pOp!=0 );
    if( pOp->opcode==OP_OpenRead && pOp->p3==iDb ){
      Index *pIndex;
................................................................................
# define isView 0
#endif
  assert( (pTrigger && tmask) || (pTrigger==0 && tmask==0) );

  /* If pTab is really a view, make sure it has been initialized.
  ** ViewGetColumnNames() is a no-op if pTab is not a view.
  */
  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto insert_cleanup;
  }

  /* Cannot insert into a read-only table.
  */
  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
    goto insert_cleanup;
................................................................................
    }

    /* Generate code to check constraints and generate index keys and
    ** do the insertion.
    */
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( IsVirtual(pTab) ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
      sqlite3VtabMakeWritable(pParse, pTab);
      sqlite3VdbeAddOp4(v, OP_VUpdate, 1, pTab->nCol+2, regIns, pVTab, P4_VTAB);
      sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
      sqlite3MayAbort(pParse);
    }else
#endif
    {
      int isReplace;    /* Set to true if constraints may cause a replace */

** run without using a temporary table for the results of the SELECT. 
*/
static int readsTable(Parse *p, int iDb, Table *pTab){
  Vdbe *v = sqlite3GetVdbe(p);
  int i;
  int iEnd = sqlite3VdbeCurrentAddr(v);
#ifndef SQLITE_OMIT_VIRTUALTABLE
  VTable *pVTab = IsVirtual(pTab) ? sqlite3GetVTable(p->db, iDb, pTab) : 0;
#endif

  for(i=1; i<iEnd; i++){
    VdbeOp *pOp = sqlite3VdbeGetOp(v, i);
    assert( pOp!=0 );
    if( pOp->opcode==OP_OpenRead && pOp->p3==iDb ){
      Index *pIndex;
................................................................................
# define isView 0
#endif
  assert( (pTrigger && tmask) || (pTrigger==0 && tmask==0) );

  /* If pTab is really a view, make sure it has been initialized.
  ** ViewGetColumnNames() is a no-op if pTab is not a view.
  */
  if( sqlite3ViewGetColumnNames(pParse, iDb, pTab) ){
    goto insert_cleanup;
  }

  /* Cannot insert into a read-only table.
  */
  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
    goto insert_cleanup;
................................................................................
    }

    /* Generate code to check constraints and generate index keys and
    ** do the insertion.
    */
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( IsVirtual(pTab) ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, iDb, pTab);
      sqlite3VtabMakeWritable(pParse, iDb, pTab);
      sqlite3VdbeAddOp4(v, OP_VUpdate, 1, pTab->nCol+2, regIns, pVTab, P4_VTAB);
      sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
      sqlite3MayAbort(pParse);
    }else
#endif
    {
      int isReplace;    /* Set to true if constraints may cause a replace */

  */
  case PragTyp_TABLE_INFO: if( zRight ){
    Table *pTab;
    pTab = sqlite3LocateTable(pParse, LOCATE_NOERR, zRight, zDb);
    if( pTab ){
      int i, k;
      int nHidden = 0;

      Column *pCol;
      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
      pParse->nMem = 7;
      sqlite3CodeVerifySchema(pParse, iDb);
      sqlite3ViewGetColumnNames(pParse, pTab);
      for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
        int isHidden = IsHiddenColumn(pCol);
        if( isHidden && pPragma->iArg==0 ){
          nHidden++;
          continue;
        }
        if( (pCol->colFlags & COLFLAG_PRIMKEY)==0 ){

  */
  case PragTyp_TABLE_INFO: if( zRight ){
    Table *pTab;
    pTab = sqlite3LocateTable(pParse, LOCATE_NOERR, zRight, zDb);
    if( pTab ){
      int i, k;
      int nHidden = 0;
      int iTabDb = sqlite3SchemaToIndex2(db, pTab->pSchema, zDb);
      Column *pCol;
      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
      pParse->nMem = 7;
      sqlite3CodeVerifySchema(pParse, iTabDb);
      sqlite3ViewGetColumnNames(pParse, iTabDb, pTab);
      for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
        int isHidden = IsHiddenColumn(pCol);
        if( isHidden && pPragma->iArg==0 ){
          nHidden++;
          continue;
        }
        if( (pCol->colFlags & COLFLAG_PRIMKEY)==0 ){

      if( !IsVirtual(pTab) && cannotBeFunction(pParse, pFrom) ){
        return WRC_Abort;
      }
#if !defined(SQLITE_OMIT_VIEW) || !defined (SQLITE_OMIT_VIRTUALTABLE)
      if( IsVirtual(pTab) || pTab->pSelect ){
        int iSave = pParse->iFixDb;
        i16 nCol;
        pParse->iFixDb = 1 + sqlite3SchemaToIndex2(
            db, pTab->pSchema, pFrom->zDatabase
        );

        if( sqlite3ViewGetColumnNames(pParse, pTab) ){
          pParse->iFixDb = iSave;
          return WRC_Abort;
        }
        assert( pFrom->pSelect==0 );
        pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect, 0);
        nCol = pTab->nCol;
        pTab->nCol = -1;

      if( !IsVirtual(pTab) && cannotBeFunction(pParse, pFrom) ){
        return WRC_Abort;
      }
#if !defined(SQLITE_OMIT_VIEW) || !defined (SQLITE_OMIT_VIRTUALTABLE)
      if( IsVirtual(pTab) || pTab->pSelect ){
        int iSave = pParse->iFixDb;
        i16 nCol;

        int iDb = sqlite3SchemaToIndex2(db, pTab->pSchema, pFrom->zDatabase);

        pParse->iFixDb = 1 + iDb;
        if( sqlite3ViewGetColumnNames(pParse, iDb, pTab) ){
          pParse->iFixDb = iSave;
          return WRC_Abort;
        }
        assert( pFrom->pSelect==0 );
        pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect, 0);
        nCol = pTab->nCol;
        pTab->nCol = -1;

** list without holding the corresponding sqlite3.mutex mutex.
**
** The memory for objects of this type is always allocated by
** sqlite3DbMalloc(), using the connection handle stored in VTable.db as
** the first argument.
*/
struct VTable {
  sqlite3 *db;              /* Database connection associated with this table */

  Module *pMod;             /* Pointer to module implementation */
  sqlite3_vtab *pVtab;      /* Pointer to vtab instance */
  int nRef;                 /* Number of pointers to this structure */
  u8 bConstraint;           /* True if constraints are supported */
  int iSavepoint;           /* Depth of the SAVEPOINT stack */
  VTable *pNext;            /* Next in linked list (see above) */
};
................................................................................
  const char *zTail;        /* All SQL text past the last semicolon parsed */
  Table *pNewTable;         /* A table being constructed by CREATE TABLE */
  Index *pNewIndex;         /* An index being constructed by CREATE INDEX */
  Trigger *pNewTrigger;     /* Trigger under construct by a CREATE TRIGGER */
  const char *zAuthContext; /* The 6th parameter to db->xAuth callbacks */
#ifndef SQLITE_OMIT_VIRTUALTABLE
  Token sArg;               /* Complete text of a module argument */
  Table **apVtabLock;       /* Pointer to virtual tables needing locking */
#endif
  Table *pZombieTab;        /* List of Table objects to delete after code gen */
  TriggerPrg *pTriggerPrg;  /* Linked list of coded triggers */
  With *pWith;              /* Current WITH clause, or NULL */
  With *pWithToFree;        /* Free this WITH object at the end of the parse */
#ifndef SQLITE_OMIT_ALTERTABLE
  RenameToken *pRename;     /* Tokens subject to renaming by ALTER TABLE */
................................................................................
void sqlite3RowSetInsert(RowSet*, i64);
int sqlite3RowSetTest(RowSet*, int iBatch, i64);
int sqlite3RowSetNext(RowSet*, i64*);

void sqlite3CreateView(Parse*,Token*,Token*,Token*,ExprList*,Select*,int,int);

#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
  int sqlite3ViewGetColumnNames(Parse*,Table*);
#else
# define sqlite3ViewGetColumnNames(A,B) 0
#endif

#if SQLITE_MAX_ATTACHED>30
  int sqlite3DbMaskAllZero(yDbMask);
#endif
void sqlite3DropTable(Parse*, SrcList*, int, int);
void sqlite3CodeDropTable(Parse*, Table*, int, int);
................................................................................
#  define sqlite3VtabRollback(X)
#  define sqlite3VtabCommit(X)
#  define sqlite3VtabInSync(db) 0
#  define sqlite3VtabLock(X)
#  define sqlite3VtabUnlock(X)
#  define sqlite3VtabUnlockList(X)
#  define sqlite3VtabSavepoint(X, Y, Z) SQLITE_OK
#  define sqlite3GetVTable(X,Y)  ((VTable*)0)
#else
   void sqlite3VtabClear(sqlite3 *db, Table*);
   void sqlite3VtabDisconnect(sqlite3 *db, Table *p);
   int sqlite3VtabSync(sqlite3 *db, Vdbe*);
   int sqlite3VtabRollback(sqlite3 *db);
   int sqlite3VtabCommit(sqlite3 *db);
   void sqlite3VtabLock(VTable *);
   void sqlite3VtabUnlock(VTable *);
   void sqlite3VtabUnlockList(sqlite3*);
   int sqlite3VtabSavepoint(sqlite3 *, int, int);
   void sqlite3VtabImportErrmsg(Vdbe*, sqlite3_vtab*);
   VTable *sqlite3GetVTable(sqlite3*, Table*);
   Module *sqlite3VtabCreateModule(
     sqlite3*,
     const char*,
     const sqlite3_module*,
     void*,
     void(*)(void*)
   );
#  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
#endif
int sqlite3VtabEponymousTableInit(Parse*,Module*);
void sqlite3VtabEponymousTableClear(sqlite3*,Module*);
void sqlite3VtabMakeWritable(Parse*,Table*);
void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*, int);
void sqlite3VtabFinishParse(Parse*, Token*);
void sqlite3VtabArgInit(Parse*);
void sqlite3VtabArgExtend(Parse*, Token*);
int sqlite3VtabCallCreate(sqlite3*, int, const char *, char **);
int sqlite3VtabCallConnect(Parse*, Table*);
int sqlite3VtabCallDestroy(sqlite3*, int, const char *);
int sqlite3VtabBegin(sqlite3 *, VTable *);
FuncDef *sqlite3VtabOverloadFunction(sqlite3 *,FuncDef*, int nArg, Expr*);
sqlite3_int64 sqlite3StmtCurrentTime(sqlite3_context*);
int sqlite3VdbeParameterIndex(Vdbe*, const char*, int);
int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
void sqlite3ParserReset(Parse*);

** list without holding the corresponding sqlite3.mutex mutex.
**
** The memory for objects of this type is always allocated by
** sqlite3DbMalloc(), using the connection handle stored in VTable.db as
** the first argument.
*/
struct VTable {
  sqlite3 *db;              /* Database that owns this virtual table */
  Btree *pBt;               /* Btree backend associated with this table */
  Module *pMod;             /* Pointer to module implementation */
  sqlite3_vtab *pVtab;      /* Pointer to vtab instance */
  int nRef;                 /* Number of pointers to this structure */
  u8 bConstraint;           /* True if constraints are supported */
  int iSavepoint;           /* Depth of the SAVEPOINT stack */
  VTable *pNext;            /* Next in linked list (see above) */
};
................................................................................
  const char *zTail;        /* All SQL text past the last semicolon parsed */
  Table *pNewTable;         /* A table being constructed by CREATE TABLE */
  Index *pNewIndex;         /* An index being constructed by CREATE INDEX */
  Trigger *pNewTrigger;     /* Trigger under construct by a CREATE TRIGGER */
  const char *zAuthContext; /* The 6th parameter to db->xAuth callbacks */
#ifndef SQLITE_OMIT_VIRTUALTABLE
  Token sArg;               /* Complete text of a module argument */
  VTable **apVtabLock;      /* Pointer to virtual tables needing locking */
#endif
  Table *pZombieTab;        /* List of Table objects to delete after code gen */
  TriggerPrg *pTriggerPrg;  /* Linked list of coded triggers */
  With *pWith;              /* Current WITH clause, or NULL */
  With *pWithToFree;        /* Free this WITH object at the end of the parse */
#ifndef SQLITE_OMIT_ALTERTABLE
  RenameToken *pRename;     /* Tokens subject to renaming by ALTER TABLE */
................................................................................
void sqlite3RowSetInsert(RowSet*, i64);
int sqlite3RowSetTest(RowSet*, int iBatch, i64);
int sqlite3RowSetNext(RowSet*, i64*);

void sqlite3CreateView(Parse*,Token*,Token*,Token*,ExprList*,Select*,int,int);

#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
  int sqlite3ViewGetColumnNames(Parse*,int,Table*);
#else
# define sqlite3ViewGetColumnNames(A,B,C) 0
#endif

#if SQLITE_MAX_ATTACHED>30
  int sqlite3DbMaskAllZero(yDbMask);
#endif
void sqlite3DropTable(Parse*, SrcList*, int, int);
void sqlite3CodeDropTable(Parse*, Table*, int, int);
................................................................................
#  define sqlite3VtabRollback(X)
#  define sqlite3VtabCommit(X)
#  define sqlite3VtabInSync(db) 0
#  define sqlite3VtabLock(X)
#  define sqlite3VtabUnlock(X)
#  define sqlite3VtabUnlockList(X)
#  define sqlite3VtabSavepoint(X, Y, Z) SQLITE_OK
#  define sqlite3GetVTable(X,Y,Z)  ((VTable*)0)
#else
   void sqlite3VtabClear(sqlite3 *db, Table*);
   void sqlite3VtabDisconnect(sqlite3 *db, Table *p);
   int sqlite3VtabSync(sqlite3 *db, Vdbe*);
   int sqlite3VtabRollback(sqlite3 *db);
   int sqlite3VtabCommit(sqlite3 *db);
   void sqlite3VtabLock(VTable *);
   void sqlite3VtabUnlock(VTable *);
   void sqlite3VtabUnlockList(sqlite3*);
   int sqlite3VtabSavepoint(sqlite3 *, int, int);
   void sqlite3VtabImportErrmsg(Vdbe*, sqlite3_vtab*);
   VTable *sqlite3GetVTable(sqlite3*, int, Table*);
   Module *sqlite3VtabCreateModule(
     sqlite3*,
     const char*,
     const sqlite3_module*,
     void*,
     void(*)(void*)
   );
#  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
#endif
int sqlite3VtabEponymousTableInit(Parse*,Module*);
void sqlite3VtabEponymousTableClear(sqlite3*,Module*);
void sqlite3VtabMakeWritable(Parse*,int,Table*);
void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*, int);
void sqlite3VtabFinishParse(Parse*, Token*);
void sqlite3VtabArgInit(Parse*);
void sqlite3VtabArgExtend(Parse*, Token*);
int sqlite3VtabCallCreate(sqlite3*, int, const char *, char **);
int sqlite3VtabCallConnect(Parse*, int, Table*);
int sqlite3VtabCallDestroy(sqlite3*, int, const char *);
int sqlite3VtabBegin(sqlite3 *, VTable *);
FuncDef *sqlite3VtabOverloadFunction(sqlite3 *,FuncDef*, int nArg, Expr*);
sqlite3_int64 sqlite3StmtCurrentTime(sqlite3_context*);
int sqlite3VdbeParameterIndex(Vdbe*, const char*, int);
int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
void sqlite3ParserReset(Parse*);

*/
#include "sqliteInt.h"

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Forward declaration */
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */

  SrcList *pSrc,       /* The virtual table to be modified */
  Table *pTab,         /* The virtual table */
  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
  Expr *pRowidExpr,    /* Expression used to recompute the rowid */
  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
  int onError          /* ON CONFLICT strategy */
................................................................................
        pParse, pTabList, pWhere, pOrderBy, pLimit, "UPDATE"
    );
    pOrderBy = 0;
    pLimit = 0;
  }
#endif

  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto update_cleanup;
  }
  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
    goto update_cleanup;
  }

  /* Allocate a cursors for the main database table and for all indices.
................................................................................
  if( sqlite3ResolveExprNames(&sNC, pWhere) ){
    goto update_cleanup;
  }

#ifndef SQLITE_OMIT_VIRTUALTABLE
  /* Virtual tables must be handled separately */
  if( IsVirtual(pTab) ){
    updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
                       pWhere, onError);
    goto update_cleanup;
  }
#endif

  /* Jump to labelBreak to abandon further processing of this UPDATE */
  labelContinue = labelBreak = sqlite3VdbeMakeLabel(v);
................................................................................
**
** The "onepass" strategy does not use an ephemeral table. Instead, it
** stores the same values (A, B and C above) in a register array and
** makes a single invocation of VUpdate.
*/
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */

  SrcList *pSrc,       /* The virtual table to be modified */
  Table *pTab,         /* The virtual table */
  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
  Expr *pRowid,        /* Expression used to recompute the rowid */
  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
  int onError          /* ON CONFLICT strategy */
){
  Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
  int ephemTab;             /* Table holding the result of the SELECT */
  int i;                    /* Loop counter */
  sqlite3 *db = pParse->db; /* Database connection */
  const char *pVTab = (const char*)sqlite3GetVTable(db, pTab);
  WhereInfo *pWInfo;
  int nArg = 2 + pTab->nCol;      /* Number of arguments to VUpdate */
  int regArg;                     /* First register in VUpdate arg array */
  int regRec;                     /* Register in which to assemble record */
  int regRowid;                   /* Register for ephem table rowid */
  int iCsr = pSrc->a[0].iCursor;  /* Cursor used for virtual table scan */
  int aDummy[2];                  /* Unused arg for sqlite3WhereOkOnePass() */
................................................................................

    /* Extract arguments from the current row of the ephemeral table and 
    ** invoke the VUpdate method.  */
    for(i=0; i<nArg; i++){
      sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i, regArg+i);
    }
  }
  sqlite3VtabMakeWritable(pParse, pTab);
  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, nArg, regArg, pVTab, P4_VTAB);
  sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
  sqlite3MayAbort(pParse);

  /* End of the ephemeral table scan. Or, if using the onepass strategy,
  ** jump to here if the scan visited zero rows. */
  if( eOnePass==ONEPASS_OFF ){

*/
#include "sqliteInt.h"

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Forward declaration */
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */
  int iDb,
  SrcList *pSrc,       /* The virtual table to be modified */
  Table *pTab,         /* The virtual table */
  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
  Expr *pRowidExpr,    /* Expression used to recompute the rowid */
  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
  int onError          /* ON CONFLICT strategy */
................................................................................
        pParse, pTabList, pWhere, pOrderBy, pLimit, "UPDATE"
    );
    pOrderBy = 0;
    pLimit = 0;
  }
#endif

  if( sqlite3ViewGetColumnNames(pParse, iDb, pTab) ){
    goto update_cleanup;
  }
  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
    goto update_cleanup;
  }

  /* Allocate a cursors for the main database table and for all indices.
................................................................................
  if( sqlite3ResolveExprNames(&sNC, pWhere) ){
    goto update_cleanup;
  }

#ifndef SQLITE_OMIT_VIRTUALTABLE
  /* Virtual tables must be handled separately */
  if( IsVirtual(pTab) ){
    updateVirtualTable(pParse, iDb, pTabList, pTab, pChanges, pRowidExpr, aXRef,
                       pWhere, onError);
    goto update_cleanup;
  }
#endif

  /* Jump to labelBreak to abandon further processing of this UPDATE */
  labelContinue = labelBreak = sqlite3VdbeMakeLabel(v);
................................................................................
**
** The "onepass" strategy does not use an ephemeral table. Instead, it
** stores the same values (A, B and C above) in a register array and
** makes a single invocation of VUpdate.
*/
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */
  int iDb,
  SrcList *pSrc,       /* The virtual table to be modified */
  Table *pTab,         /* The virtual table */
  ExprList *pChanges,  /* The columns to change in the UPDATE statement */
  Expr *pRowid,        /* Expression used to recompute the rowid */
  int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
  Expr *pWhere,        /* WHERE clause of the UPDATE statement */
  int onError          /* ON CONFLICT strategy */
){
  Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
  int ephemTab;             /* Table holding the result of the SELECT */
  int i;                    /* Loop counter */
  sqlite3 *db = pParse->db; /* Database connection */
  const char *pVTab = (const char*)sqlite3GetVTable(db, iDb, pTab);
  WhereInfo *pWInfo;
  int nArg = 2 + pTab->nCol;      /* Number of arguments to VUpdate */
  int regArg;                     /* First register in VUpdate arg array */
  int regRec;                     /* Register in which to assemble record */
  int regRowid;                   /* Register for ephem table rowid */
  int iCsr = pSrc->a[0].iCursor;  /* Cursor used for virtual table scan */
  int aDummy[2];                  /* Unused arg for sqlite3WhereOkOnePass() */
................................................................................

    /* Extract arguments from the current row of the ephemeral table and 
    ** invoke the VUpdate method.  */
    for(i=0; i<nArg; i++){
      sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i, regArg+i);
    }
  }
  sqlite3VtabMakeWritable(pParse, iDb, pTab);
  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, nArg, regArg, pVTab, P4_VTAB);
  sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
  sqlite3MayAbort(pParse);

  /* End of the ephemeral table scan. Or, if using the onepass strategy,
  ** jump to here if the scan visited zero rows. */
  if( eOnePass==ONEPASS_OFF ){

/*
** pTab is a pointer to a Table structure representing a virtual-table.
** Return a pointer to the VTable object used by connection db to access 
** this virtual-table, if one has been created, or NULL otherwise.
*/
VTable *sqlite3GetVTable(sqlite3 *db, Table *pTab){
  VTable *pVtab;
  assert( IsVirtual(pTab) );




  for(pVtab=pTab->pVTable; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);

  return pVtab;
}

/*
** Decrement the ref-count on a virtual table object. When the ref-count
** reaches zero, call the xDisconnect() method to delete the object.
*/
................................................................................
** list in p->pVTab. It also decrements the VTable ref count. This is
** used when closing database connection db to free all of its VTable
** objects without disturbing the rest of the Schema object (which may
** be being used by other shared-cache connections).
*/
void sqlite3VtabDisconnect(sqlite3 *db, Table *p){
  VTable **ppVTab;


  assert( IsVirtual(p) );
  assert( sqlite3BtreeHoldsAllMutexes(db) );
  assert( sqlite3_mutex_held(db->mutex) );

  for(ppVTab=&p->pVTable; *ppVTab; ppVTab=&(*ppVTab)->pNext){
    if( (*ppVTab)->db==db  ){
      VTable *pVTab = *ppVTab;
      *ppVTab = pVTab->pNext;
      sqlite3VtabUnlock(pVTab);
      break;

    }
  }
}


/*
** Disconnect all the virtual table objects in the sqlite3.pDisconnect list.
................................................................................
/*
** Invoke a virtual table constructor (either xCreate or xConnect). The
** pointer to the function to invoke is passed as the fourth parameter
** to this procedure.
*/
static int vtabCallConstructor(
  sqlite3 *db, 

  Table *pTab,
  Module *pMod,
  int (*xConstruct)(sqlite3*,void*,int,const char*const*,sqlite3_vtab**,char**),
  char **pzErr
){
  VtabCtx sCtx;
  VTable *pVTable;
  int rc;
  const char *const*azArg = (const char *const*)pTab->azModuleArg;
  int nArg = pTab->nModuleArg;
  char *zErr = 0;
  char *zModuleName;
  int iDb;
  VtabCtx *pCtx;

  /* Check that the virtual-table is not already being initialized */
  for(pCtx=db->pVtabCtx; pCtx; pCtx=pCtx->pPrior){
    if( pCtx->pTab==pTab ){
      *pzErr = sqlite3MPrintf(db, 
          "vtable constructor called recursively: %s", pTab->zName
................................................................................
  pVTable = sqlite3MallocZero(sizeof(VTable));
  if( !pVTable ){
    sqlite3OomFault(db);
    sqlite3DbFree(db, zModuleName);
    return SQLITE_NOMEM_BKPT;
  }
  pVTable->db = db;

  pVTable->pMod = pMod;

  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  pTab->azModuleArg[1] = db->aDb[iDb].zDbSName;

  /* Invoke the virtual table constructor */
  assert( &db->pVtabCtx );
  assert( xConstruct );
  sCtx.pTab = pTab;
  sCtx.pVTable = pVTable;
................................................................................
/*
** This function is invoked by the parser to call the xConnect() method
** of the virtual table pTab. If an error occurs, an error code is returned 
** and an error left in pParse.
**
** This call is a no-op if table pTab is not a virtual table.
*/
int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
  sqlite3 *db = pParse->db;
  const char *zMod;
  Module *pMod;
  int rc;

  assert( pTab );
  if( !IsVirtual(pTab) || sqlite3GetVTable(db, pTab) ){
    return SQLITE_OK;
  }

  /* Locate the required virtual table module */
  zMod = pTab->azModuleArg[0];
  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod);

  if( !pMod ){
    const char *zModule = pTab->azModuleArg[0];
    sqlite3ErrorMsg(pParse, "no such module: %s", zModule);
    rc = SQLITE_ERROR;
  }else{
    char *zErr = 0;
    rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xConnect, &zErr);
    if( rc!=SQLITE_OK ){
      sqlite3ErrorMsg(pParse, "%s", zErr);
      pParse->rc = rc;
    }
    sqlite3DbFree(db, zErr);
  }

................................................................................
  ** invoke it now. If the module has not been registered, return an 
  ** error. Otherwise, do nothing.
  */
  if( pMod==0 || pMod->pModule->xCreate==0 || pMod->pModule->xDestroy==0 ){
    *pzErr = sqlite3MPrintf(db, "no such module: %s", zMod);
    rc = SQLITE_ERROR;
  }else{
    rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xCreate, pzErr);
  }

  /* Justification of ALWAYS():  The xConstructor method is required to
  ** create a valid sqlite3_vtab if it returns SQLITE_OK. */
  if( rc==SQLITE_OK && ALWAYS(sqlite3GetVTable(db, pTab)) ){
    rc = growVTrans(db);
    if( rc==SQLITE_OK ){
      addToVTrans(db, sqlite3GetVTable(db, pTab));
    }
  }

  return rc;
}

/*
................................................................................

  /* Check to see the left operand is a column in a virtual table */
  if( NEVER(pExpr==0) ) return pDef;
  if( pExpr->op!=TK_COLUMN ) return pDef;
  pTab = pExpr->y.pTab;
  if( pTab==0 ) return pDef;
  if( !IsVirtual(pTab) ) return pDef;
  pVtab = sqlite3GetVTable(db, pTab)->pVtab;
  assert( pVtab!=0 );
  assert( pVtab->pModule!=0 );
  pMod = (sqlite3_module *)pVtab->pModule;
  if( pMod->xFindFunction==0 ) return pDef;
 
  /* Call the xFindFunction method on the virtual table implementation
  ** to see if the implementation wants to overload this function.
................................................................................

/*
** Make sure virtual table pTab is contained in the pParse->apVirtualLock[]
** array so that an OP_VBegin will get generated for it.  Add pTab to the
** array if it is missing.  If pTab is already in the array, this routine
** is a no-op.
*/
void sqlite3VtabMakeWritable(Parse *pParse, Table *pTab){
  Parse *pToplevel = sqlite3ParseToplevel(pParse);

  int i, n;
  Table **apVtabLock;

  assert( IsVirtual(pTab) );
  for(i=0; i<pToplevel->nVtabLock; i++){
    if( pTab==pToplevel->apVtabLock[i] ) return;
  }
  n = (pToplevel->nVtabLock+1)*sizeof(pToplevel->apVtabLock[0]);
  apVtabLock = sqlite3_realloc64(pToplevel->apVtabLock, n);
  if( apVtabLock ){
    pToplevel->apVtabLock = apVtabLock;
    pToplevel->apVtabLock[pToplevel->nVtabLock++] = pTab;
  }else{
    sqlite3OomFault(pToplevel->db);
  }
}

/*
** Check to see if virtual table module pMod can be have an eponymous
................................................................................
  pTab->nTabRef = 1;
  pTab->pSchema = db->aDb[0].pSchema;
  assert( pTab->nModuleArg==0 );
  pTab->iPKey = -1;
  addModuleArgument(db, pTab, sqlite3DbStrDup(db, pTab->zName));
  addModuleArgument(db, pTab, 0);
  addModuleArgument(db, pTab, sqlite3DbStrDup(db, pTab->zName));
  rc = vtabCallConstructor(db, pTab, pMod, pModule->xConnect, &zErr);
  if( rc ){
    sqlite3ErrorMsg(pParse, "%s", zErr);
    sqlite3DbFree(db, zErr);
    sqlite3VtabEponymousTableClear(db, pMod);
    return 0;
  }
  return 1;

/*
** pTab is a pointer to a Table structure representing a virtual-table.
** Return a pointer to the VTable object used by connection db to access 
** this virtual-table, if one has been created, or NULL otherwise.
*/
VTable *sqlite3GetVTable(sqlite3 *db, int iDb, Table *pTab){
  VTable *pVtab;
  assert( IsVirtual(pTab) );
  if( iDb>=0 ){
    Btree *pBt = db->aDb[iDb].pBt;
    for(pVtab=pTab->pVTable; pVtab && pVtab->pBt!=pBt; pVtab=pVtab->pNext);
  }else{
    for(pVtab=pTab->pVTable; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);
  }
  return pVtab;
}

/*
** Decrement the ref-count on a virtual table object. When the ref-count
** reaches zero, call the xDisconnect() method to delete the object.
*/
................................................................................
** list in p->pVTab. It also decrements the VTable ref count. This is
** used when closing database connection db to free all of its VTable
** objects without disturbing the rest of the Schema object (which may
** be being used by other shared-cache connections).
*/
void sqlite3VtabDisconnect(sqlite3 *db, Table *p){
  VTable **ppVTab;
  VTable **ppNext;

  assert( IsVirtual(p) );
  assert( sqlite3BtreeHoldsAllMutexes(db) );
  assert( sqlite3_mutex_held(db->mutex) );

  for(ppVTab=&p->pVTable; *ppVTab; ){
    if( (*ppVTab)->db==db  ){
      VTable *pVTab = *ppVTab;
      *ppVTab = pVTab->pNext;
      sqlite3VtabUnlock(pVTab);
    }else{
      ppVTab = &(*ppVTab)->pNext;
    }
  }
}


/*
** Disconnect all the virtual table objects in the sqlite3.pDisconnect list.
................................................................................
/*
** Invoke a virtual table constructor (either xCreate or xConnect). The
** pointer to the function to invoke is passed as the fourth parameter
** to this procedure.
*/
static int vtabCallConstructor(
  sqlite3 *db, 
  int iDb,                        /* Database containing pTab */
  Table *pTab,
  Module *pMod,
  int (*xConstruct)(sqlite3*,void*,int,const char*const*,sqlite3_vtab**,char**),
  char **pzErr
){
  VtabCtx sCtx;
  VTable *pVTable;
  int rc;
  const char *const*azArg = (const char *const*)pTab->azModuleArg;
  int nArg = pTab->nModuleArg;
  char *zErr = 0;
  char *zModuleName;

  VtabCtx *pCtx;

  /* Check that the virtual-table is not already being initialized */
  for(pCtx=db->pVtabCtx; pCtx; pCtx=pCtx->pPrior){
    if( pCtx->pTab==pTab ){
      *pzErr = sqlite3MPrintf(db, 
          "vtable constructor called recursively: %s", pTab->zName
................................................................................
  pVTable = sqlite3MallocZero(sizeof(VTable));
  if( !pVTable ){
    sqlite3OomFault(db);
    sqlite3DbFree(db, zModuleName);
    return SQLITE_NOMEM_BKPT;
  }
  pVTable->db = db;
  pVTable->pBt = db->aDb[iDb].pBt;
  pVTable->pMod = pMod;


  pTab->azModuleArg[1] = db->aDb[iDb].zDbSName;

  /* Invoke the virtual table constructor */
  assert( &db->pVtabCtx );
  assert( xConstruct );
  sCtx.pTab = pTab;
  sCtx.pVTable = pVTable;
................................................................................
/*
** This function is invoked by the parser to call the xConnect() method
** of the virtual table pTab. If an error occurs, an error code is returned 
** and an error left in pParse.
**
** This call is a no-op if table pTab is not a virtual table.
*/
int sqlite3VtabCallConnect(Parse *pParse, int iDb, Table *pTab){
  sqlite3 *db = pParse->db;
  const char *zMod;
  Module *pMod;
  int rc;

  assert( pTab );
  if( !IsVirtual(pTab) || sqlite3GetVTable(db, iDb, pTab) ){
    return SQLITE_OK;
  }

  /* Locate the required virtual table module */
  zMod = pTab->azModuleArg[0];
  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod);

  if( !pMod ){
    const char *zModule = pTab->azModuleArg[0];
    sqlite3ErrorMsg(pParse, "no such module: %s", zModule);
    rc = SQLITE_ERROR;
  }else{
    char *zErr = 0;
    rc = vtabCallConstructor(db, iDb, pTab, pMod,pMod->pModule->xConnect,&zErr);
    if( rc!=SQLITE_OK ){
      sqlite3ErrorMsg(pParse, "%s", zErr);
      pParse->rc = rc;
    }
    sqlite3DbFree(db, zErr);
  }

................................................................................
  ** invoke it now. If the module has not been registered, return an 
  ** error. Otherwise, do nothing.
  */
  if( pMod==0 || pMod->pModule->xCreate==0 || pMod->pModule->xDestroy==0 ){
    *pzErr = sqlite3MPrintf(db, "no such module: %s", zMod);
    rc = SQLITE_ERROR;
  }else{
    rc = vtabCallConstructor(db, iDb, pTab, pMod, pMod->pModule->xCreate,pzErr);
  }

  /* Justification of ALWAYS():  The xConstructor method is required to
  ** create a valid sqlite3_vtab if it returns SQLITE_OK. */
  if( rc==SQLITE_OK && ALWAYS(sqlite3GetVTable(db, iDb, pTab)) ){
    rc = growVTrans(db);
    if( rc==SQLITE_OK ){
      addToVTrans(db, sqlite3GetVTable(db, iDb, pTab));
    }
  }

  return rc;
}

/*
................................................................................

  /* Check to see the left operand is a column in a virtual table */
  if( NEVER(pExpr==0) ) return pDef;
  if( pExpr->op!=TK_COLUMN ) return pDef;
  pTab = pExpr->y.pTab;
  if( pTab==0 ) return pDef;
  if( !IsVirtual(pTab) ) return pDef;
  pVtab = sqlite3GetVTable(db, -1, pTab)->pVtab;
  assert( pVtab!=0 );
  assert( pVtab->pModule!=0 );
  pMod = (sqlite3_module *)pVtab->pModule;
  if( pMod->xFindFunction==0 ) return pDef;
 
  /* Call the xFindFunction method on the virtual table implementation
  ** to see if the implementation wants to overload this function.
................................................................................

/*
** Make sure virtual table pTab is contained in the pParse->apVirtualLock[]
** array so that an OP_VBegin will get generated for it.  Add pTab to the
** array if it is missing.  If pTab is already in the array, this routine
** is a no-op.
*/
void sqlite3VtabMakeWritable(Parse *pParse, int iDb, Table *pTab){
  Parse *pToplevel = sqlite3ParseToplevel(pParse);
  VTable *pVTab = sqlite3GetVTable(pParse->db, iDb, pTab);
  int i, n;
  VTable **apVtabLock;

  assert( IsVirtual(pTab) );
  for(i=0; i<pToplevel->nVtabLock; i++){
    if( pVTab==pToplevel->apVtabLock[i] ) return;
  }
  n = (pToplevel->nVtabLock+1)*sizeof(pToplevel->apVtabLock[0]);
  apVtabLock = sqlite3_realloc64(pToplevel->apVtabLock, n);
  if( apVtabLock ){
    pToplevel->apVtabLock = apVtabLock;
    pToplevel->apVtabLock[pToplevel->nVtabLock++] = pVTab;
  }else{
    sqlite3OomFault(pToplevel->db);
  }
}

/*
** Check to see if virtual table module pMod can be have an eponymous
................................................................................
  pTab->nTabRef = 1;
  pTab->pSchema = db->aDb[0].pSchema;
  assert( pTab->nModuleArg==0 );
  pTab->iPKey = -1;
  addModuleArgument(db, pTab, sqlite3DbStrDup(db, pTab->zName));
  addModuleArgument(db, pTab, 0);
  addModuleArgument(db, pTab, sqlite3DbStrDup(db, pTab->zName));
  rc = vtabCallConstructor(db, 0, pTab, pMod, pModule->xConnect, &zErr);
  if( rc ){
    sqlite3ErrorMsg(pParse, "%s", zErr);
    sqlite3DbFree(db, zErr);
    sqlite3VtabEponymousTableClear(db, pMod);
    return 0;
  }
  return 1;

** the current configuration of "unusable" flags in sqlite3_index_info can
** not result in a valid plan.
**
** Whether or not an error is returned, it is the responsibility of the
** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
** that this is required.
*/
static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){






  sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
  int rc;

  TRACE_IDX_INPUTS(p);
  rc = pVtab->pModule->xBestIndex(pVtab, p);
  TRACE_IDX_OUTPUTS(p);

  if( rc!=SQLITE_OK && rc!=SQLITE_CONSTRAINT ){
................................................................................
  pIdxInfo->orderByConsumed = 0;
  pIdxInfo->estimatedCost = SQLITE_BIG_DBL / (double)2;
  pIdxInfo->estimatedRows = 25;
  pIdxInfo->idxFlags = 0;
  pIdxInfo->colUsed = (sqlite3_int64)pSrc->colUsed;

  /* Invoke the virtual table xBestIndex() method */
  rc = vtabBestIndex(pParse, pSrc->pTab, pIdxInfo);
  if( rc ){
    if( rc==SQLITE_CONSTRAINT ){
      /* If the xBestIndex method returns SQLITE_CONSTRAINT, that means
      ** that the particular combination of parameters provided is unusable.
      ** Make no entries in the loop table.
      */
      WHERETRACE(0xffff, ("  ^^^^--- non-viable plan rejected!\n"));
................................................................................
    iDb = sqlite3SchemaToIndex2(db, pTab->pSchema, pTabItem->zDatabase);
    pLoop = pLevel->pWLoop;
    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
      /* Do nothing */
    }else
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
      int iCur = pTabItem->iCursor;
      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
    }else if( IsVirtual(pTab) ){
      /* noop */
    }else
#endif
    if( (pLoop->wsFlags & WHERE_IDX_ONLY)==0

** the current configuration of "unusable" flags in sqlite3_index_info can
** not result in a valid plan.
**
** Whether or not an error is returned, it is the responsibility of the
** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
** that this is required.
*/
static int vtabBestIndex(
  Parse *pParse, 
  struct SrcList_item *pSrc, 
  sqlite3_index_info *p
){
  Table *pTab = pSrc->pTab;
  int iDb = sqlite3SchemaToIndex2(pParse->db, pTab->pSchema, pSrc->zDatabase);
  sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, iDb, pTab)->pVtab;
  int rc;

  TRACE_IDX_INPUTS(p);
  rc = pVtab->pModule->xBestIndex(pVtab, p);
  TRACE_IDX_OUTPUTS(p);

  if( rc!=SQLITE_OK && rc!=SQLITE_CONSTRAINT ){
................................................................................
  pIdxInfo->orderByConsumed = 0;
  pIdxInfo->estimatedCost = SQLITE_BIG_DBL / (double)2;
  pIdxInfo->estimatedRows = 25;
  pIdxInfo->idxFlags = 0;
  pIdxInfo->colUsed = (sqlite3_int64)pSrc->colUsed;

  /* Invoke the virtual table xBestIndex() method */
  rc = vtabBestIndex(pParse, pSrc, pIdxInfo);
  if( rc ){
    if( rc==SQLITE_CONSTRAINT ){
      /* If the xBestIndex method returns SQLITE_CONSTRAINT, that means
      ** that the particular combination of parameters provided is unusable.
      ** Make no entries in the loop table.
      */
      WHERETRACE(0xffff, ("  ^^^^--- non-viable plan rejected!\n"));
................................................................................
    iDb = sqlite3SchemaToIndex2(db, pTab->pSchema, pTabItem->zDatabase);
    pLoop = pLevel->pWLoop;
    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
      /* Do nothing */
    }else
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, iDb, pTab);
      int iCur = pTabItem->iCursor;
      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
    }else if( IsVirtual(pTab) ){
      /* noop */
    }else
#endif
    if( (pLoop->wsFlags & WHERE_IDX_ONLY)==0

    */
    pCol = pList->a[0].pExpr;
    if( pCol->op==TK_COLUMN && IsVirtual(pCol->y.pTab) ){
      sqlite3_vtab *pVtab;
      sqlite3_module *pMod;
      void (*xNotUsed)(sqlite3_context*,int,sqlite3_value**);
      void *pNotUsed;
      pVtab = sqlite3GetVTable(db, pCol->y.pTab)->pVtab;
      assert( pVtab!=0 );
      assert( pVtab->pModule!=0 );
      pMod = (sqlite3_module *)pVtab->pModule;
      if( pMod->xFindFunction!=0 ){
        i = pMod->xFindFunction(pVtab,2, pExpr->u.zToken, &xNotUsed, &pNotUsed);
        if( i>=SQLITE_INDEX_CONSTRAINT_FUNCTION ){
          *peOp2 = i;

    */
    pCol = pList->a[0].pExpr;
    if( pCol->op==TK_COLUMN && IsVirtual(pCol->y.pTab) ){
      sqlite3_vtab *pVtab;
      sqlite3_module *pMod;
      void (*xNotUsed)(sqlite3_context*,int,sqlite3_value**);
      void *pNotUsed;
      pVtab = sqlite3GetVTable(db, -1, pCol->y.pTab)->pVtab;
      assert( pVtab!=0 );
      assert( pVtab->pModule!=0 );
      pMod = (sqlite3_module *)pVtab->pModule;
      if( pMod->xFindFunction!=0 ){
        i = pMod->xFindFunction(pVtab,2, pExpr->u.zToken, &xNotUsed, &pNotUsed);
        if( i>=SQLITE_INDEX_CONSTRAINT_FUNCTION ){
          *peOp2 = i;