SQLite

  ** and code in pParse and return NULL. */
  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
    return 0;
  }

  p = sqlite3FindTable(pParse->db, zName, zDbase);
  if( p==0 ){
#ifndef SQLITE_OMIT_VIRTUAL_TABLE
    /* If zName is the not the name of a table in the schema created using
    ** CREATE, then check to see if it is the name of an virtual table that
    ** can be an eponymous virtual table. */
    Module *pMod = (Module*)sqlite3HashFind(&pParse->db->aModule, zName);
    if( pMod && sqlite3VtabEponymousTableInit(pParse, pMod) ){
      return pMod->pEpoTab;
    }
#endif
    const char *zMsg = isView ? "no such view" : "no such table";
    if( zDbase ){
      sqlite3ErrorMsg(pParse, "%s: %s.%s", zMsg, zDbase, zName);
    }else{
      sqlite3ErrorMsg(pParse, "%s: %s", zMsg, zName);
    }
    pParse->checkSchema = 1;

  db->flags &= ~SQLITE_InternChanges;
}

/*
** Delete memory allocated for the column names of a table or view (the
** Table.aCol[] array).
*/
void sqlite3DeleteColumnNames(sqlite3 *db, Table *pTable){
  int i;
  Column *pCol;
  assert( pTable!=0 );
  if( (pCol = pTable->aCol)!=0 ){
    for(i=0; i<pTable->nCol; i++, pCol++){
      sqlite3DbFree(db, pCol->zName);
      sqlite3ExprDelete(db, pCol->pDflt);

  }

  /* Delete any foreign keys attached to this table. */
  sqlite3FkDelete(db, pTable);

  /* Delete the Table structure itself.
  */
  sqlite3DeleteColumnNames(db, pTable);
  sqlite3DbFree(db, pTable->zName);
  sqlite3DbFree(db, pTable->zColAff);
  sqlite3SelectDelete(db, pTable->pSelect);
#ifndef SQLITE_OMIT_CHECK
  sqlite3ExprListDelete(db, pTable->pCheck);
#endif
#ifndef SQLITE_OMIT_VIRTUALTABLE

static void sqliteViewResetAll(sqlite3 *db, int idx){
  HashElem *i;
  assert( sqlite3SchemaMutexHeld(db, idx, 0) );
  if( !DbHasProperty(db, idx, DB_UnresetViews) ) return;
  for(i=sqliteHashFirst(&db->aDb[idx].pSchema->tblHash); i;i=sqliteHashNext(i)){
    Table *pTab = sqliteHashData(i);
    if( pTab->pSelect ){
      sqlite3DeleteColumnNames(db, pTab);
      pTab->aCol = 0;
      pTab->nCol = 0;
    }
  }
  DbClearProperty(db, idx, DB_UnresetViews);
}
#else

/*
** Disconnect all sqlite3_vtab objects that belong to database connection
** db. This is called when db is being closed.
*/
static void disconnectAllVtab(sqlite3 *db){
#ifndef SQLITE_OMIT_VIRTUALTABLE
  int i;
  HashElem *p;
  sqlite3BtreeEnterAll(db);
  for(i=0; i<db->nDb; i++){
    Schema *pSchema = db->aDb[i].pSchema;
    if( db->aDb[i].pSchema ){

      for(p=sqliteHashFirst(&pSchema->tblHash); p; p=sqliteHashNext(p)){
        Table *pTab = (Table *)sqliteHashData(p);
        if( IsVirtual(pTab) ) sqlite3VtabDisconnect(db, pTab);
      }
    }
  }
  for(p=sqliteHashFirst(&db->aModule); p; p=sqliteHashNext(p)){
    Module *pMod = (Module *)sqliteHashData(p);
    if( pMod->pEpoTab ){
      sqlite3VtabDisconnect(db, pMod->pEpoTab);
    }
  }
  sqlite3VtabUnlockList(db);
  sqlite3BtreeLeaveAll(db);
#else
  UNUSED_PARAMETER(db);
#endif
}

  sqlite3HashClear(&db->aCollSeq);
#ifndef SQLITE_OMIT_VIRTUALTABLE
  for(i=sqliteHashFirst(&db->aModule); i; i=sqliteHashNext(i)){
    Module *pMod = (Module *)sqliteHashData(i);
    if( pMod->xDestroy ){
      pMod->xDestroy(pMod->pAux);
    }
    sqlite3VtabEponymousTableClear(db, pMod);
    sqlite3DbFree(db, pMod);
  }
  sqlite3HashClear(&db->aModule);
#endif

  sqlite3Error(db, SQLITE_OK); /* Deallocates any cached error strings. */
  sqlite3ValueFree(db->pErr);

** hash table.
*/
struct Module {
  const sqlite3_module *pModule;       /* Callback pointers */
  const char *zName;                   /* Name passed to create_module() */
  void *pAux;                          /* pAux passed to create_module() */
  void (*xDestroy)(void *);            /* Module destructor function */
  Table *pEpoTab;                      /* Eponymous table for this module */
};

/*
** information about each column of an SQL table is held in an instance
** of this structure.
*/
struct Column {

int sqlite3InitCallback(void*, int, char**, char**);
void sqlite3Pragma(Parse*,Token*,Token*,Token*,int);
void sqlite3ResetAllSchemasOfConnection(sqlite3*);
void sqlite3ResetOneSchema(sqlite3*,int);
void sqlite3CollapseDatabaseArray(sqlite3*);
void sqlite3BeginParse(Parse*,int);
void sqlite3CommitInternalChanges(sqlite3*);
void sqlite3DeleteColumnNames(sqlite3*,Table*);
Table *sqlite3ResultSetOfSelect(Parse*,Select*);
void sqlite3OpenMasterTable(Parse *, int);
Index *sqlite3PrimaryKeyIndex(Table*);
i16 sqlite3ColumnOfIndex(Index*, i16);
void sqlite3StartTable(Parse*,Token*,Token*,int,int,int,int);
void sqlite3AddColumn(Parse*,Token*);
void sqlite3AddNotNull(Parse*, int);

   void sqlite3VtabUnlock(VTable *);
   void sqlite3VtabUnlockList(sqlite3*);
   int sqlite3VtabSavepoint(sqlite3 *, int, int);
   void sqlite3VtabImportErrmsg(Vdbe*, sqlite3_vtab*);
   VTable *sqlite3GetVTable(sqlite3*, Table*);
#  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*);

      Module *pDel;
      char *zCopy = (char *)(&pMod[1]);
      memcpy(zCopy, zName, nName+1);
      pMod->zName = zCopy;
      pMod->pModule = pModule;
      pMod->pAux = pAux;
      pMod->xDestroy = xDestroy;
      pMod->pEpoTab = 0;
      pDel = (Module *)sqlite3HashInsert(&db->aModule,zCopy,(void*)pMod);
      assert( pDel==0 || pDel==pMod );
      if( pDel ){
        db->mallocFailed = 1;
        sqlite3DbFree(db, pDel);
      }
    }

  if( !db || db->pnBytesFreed==0 ) vtabDisconnectAll(0, p);
  if( p->azModuleArg ){
    int i;
    for(i=0; i<p->nModuleArg; i++){
      if( i!=1 ) sqlite3DbFree(db, p->azModuleArg[i]);
    }
    sqlite3DbFree(db, p->azModuleArg);
    p->azModuleArg = 0;
  }
}

/*
** Add a new module argument to pTable->azModuleArg[].
** The string is not copied - the pointer is stored.  The
** string will be freed automatically when the table is

  if( apVtabLock ){
    pToplevel->apVtabLock = apVtabLock;
    pToplevel->apVtabLock[pToplevel->nVtabLock++] = pTab;
  }else{
    pToplevel->db->mallocFailed = 1;
  }
}

/*
** Check to see if virtual tale module pMod can be have an eponymous
** virtual table instance.  If it can, create one if one does not already
** exist. Return non-zero if the eponymous virtual table instance exists
** when this routine returns, and return zero if it does not exist.
**
** An eponymous virtual table instance is one that is named after its
** module, and more importantly, does not require a CREATE VIRTUAL TABLE
** statement in order to come into existance.  Eponymous virtual table
** instances always exist.  They cannot be DROP-ed.
**
** Any virtual table module for which xConnect and xCreate are the same
** method can have an eponymous virtual table instance.
*/
int sqlite3VtabEponymousTableInit(Parse *pParse, Module *pMod){
  const sqlite3_module *pModule = pMod->pModule;
  Table *pTab;
  char *zErr = 0;
  int nName;
  int rc;
  sqlite3 *db = pParse->db;
  if( pMod->pEpoTab ) return 1;
  if( pModule->xCreate!=pModule->xConnect ) return 0;
  nName = sqlite3Strlen30(pMod->zName) + 1;
  pTab = sqlite3DbMallocZero(db, sizeof(Table) + nName);
  if( pTab==0 ) return 0;
  pMod->pEpoTab = pTab;
  pTab->zName = (char*)&pTab[1];
  memcpy(pTab->zName, pMod->zName, nName);
  pTab->nRef = 1;
  pTab->pSchema = db->aDb[0].pSchema;
  pTab->tabFlags |= TF_Virtual;
  pTab->nModuleArg = 0;
  addModuleArgument(db, pTab, pTab->zName);
  addModuleArgument(db, pTab, 0);
  addModuleArgument(db, pTab, 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;
}

/*
** Erase the eponymous virtual table instance associated with
** virtual table module pMod, if it exists.
*/
void sqlite3VtabEponymousTableClear(sqlite3 *db, Module *pMod){
  Table *pTab = pMod->pEpoTab;
  if( (pTab = pMod->pEpoTab)!=0 ){
    sqlite3DeleteColumnNames(db, pTab);
    sqlite3DbFree(db, pTab->azModuleArg);
    sqlite3DbFree(db, pTab);
    pMod->pEpoTab = 0;
  }
}

/*
** Return the ON CONFLICT resolution mode in effect for the virtual
** table update operation currently in progress.
**
** The results of this routine are undefined unless it is called from
** within an xUpdate method.