xref: /sqlite-3.40.0/src/vtab.c (revision ddfec00d)
1 /*
2 ** 2006 June 10
3 **
4 ** The author disclaims copyright to this source code.  In place of
5 ** a legal notice, here is a blessing:
6 **
7 **    May you do good and not evil.
8 **    May you find forgiveness for yourself and forgive others.
9 **    May you share freely, never taking more than you give.
10 **
11 *************************************************************************
12 ** This file contains code used to help implement virtual tables.
13 */
14 #ifndef SQLITE_OMIT_VIRTUALTABLE
15 #include "sqliteInt.h"
16 
17 /*
18 ** Before a virtual table xCreate() or xConnect() method is invoked, the
19 ** sqlite3.pVtabCtx member variable is set to point to an instance of
20 ** this struct allocated on the stack. It is used by the implementation of
21 ** the sqlite3_declare_vtab() and sqlite3_vtab_config() APIs, both of which
22 ** are invoked only from within xCreate and xConnect methods.
23 */
24 struct VtabCtx {
25   VTable *pVTable;    /* The virtual table being constructed */
26   Table *pTab;        /* The Table object to which the virtual table belongs */
27   VtabCtx *pPrior;    /* Parent context (if any) */
28   int bDeclared;      /* True after sqlite3_declare_vtab() is called */
29 };
30 
31 /*
32 ** Construct and install a Module object for a virtual table.  When this
33 ** routine is called, it is guaranteed that all appropriate locks are held
34 ** and the module is not already part of the connection.
35 **
36 ** If there already exists a module with zName, replace it with the new one.
37 ** If pModule==0, then delete the module zName if it exists.
38 */
39 Module *sqlite3VtabCreateModule(
40   sqlite3 *db,                    /* Database in which module is registered */
41   const char *zName,              /* Name assigned to this module */
42   const sqlite3_module *pModule,  /* The definition of the module */
43   void *pAux,                     /* Context pointer for xCreate/xConnect */
44   void (*xDestroy)(void *)        /* Module destructor function */
45 ){
46   Module *pMod;
47   Module *pDel;
48   char *zCopy;
49   if( pModule==0 ){
50     zCopy = (char*)zName;
51     pMod = 0;
52   }else{
53     int nName = sqlite3Strlen30(zName);
54     pMod = (Module *)sqlite3Malloc(sizeof(Module) + nName + 1);
55     if( pMod==0 ){
56       sqlite3OomFault(db);
57       return 0;
58     }
59     zCopy = (char *)(&pMod[1]);
60     memcpy(zCopy, zName, nName+1);
61     pMod->zName = zCopy;
62     pMod->pModule = pModule;
63     pMod->pAux = pAux;
64     pMod->xDestroy = xDestroy;
65     pMod->pEpoTab = 0;
66     pMod->nRefModule = 1;
67   }
68   pDel = (Module *)sqlite3HashInsert(&db->aModule,zCopy,(void*)pMod);
69   if( pDel ){
70     if( pDel==pMod ){
71       sqlite3OomFault(db);
72       sqlite3DbFree(db, pDel);
73       pMod = 0;
74     }else{
75       sqlite3VtabEponymousTableClear(db, pDel);
76       sqlite3VtabModuleUnref(db, pDel);
77     }
78   }
79   return pMod;
80 }
81 
82 /*
83 ** The actual function that does the work of creating a new module.
84 ** This function implements the sqlite3_create_module() and
85 ** sqlite3_create_module_v2() interfaces.
86 */
87 static int createModule(
88   sqlite3 *db,                    /* Database in which module is registered */
89   const char *zName,              /* Name assigned to this module */
90   const sqlite3_module *pModule,  /* The definition of the module */
91   void *pAux,                     /* Context pointer for xCreate/xConnect */
92   void (*xDestroy)(void *)        /* Module destructor function */
93 ){
94   int rc = SQLITE_OK;
95 
96   sqlite3_mutex_enter(db->mutex);
97   (void)sqlite3VtabCreateModule(db, zName, pModule, pAux, xDestroy);
98   rc = sqlite3ApiExit(db, rc);
99   if( rc!=SQLITE_OK && xDestroy ) xDestroy(pAux);
100   sqlite3_mutex_leave(db->mutex);
101   return rc;
102 }
103 
104 
105 /*
106 ** External API function used to create a new virtual-table module.
107 */
108 int sqlite3_create_module(
109   sqlite3 *db,                    /* Database in which module is registered */
110   const char *zName,              /* Name assigned to this module */
111   const sqlite3_module *pModule,  /* The definition of the module */
112   void *pAux                      /* Context pointer for xCreate/xConnect */
113 ){
114 #ifdef SQLITE_ENABLE_API_ARMOR
115   if( !sqlite3SafetyCheckOk(db) || zName==0 ) return SQLITE_MISUSE_BKPT;
116 #endif
117   return createModule(db, zName, pModule, pAux, 0);
118 }
119 
120 /*
121 ** External API function used to create a new virtual-table module.
122 */
123 int sqlite3_create_module_v2(
124   sqlite3 *db,                    /* Database in which module is registered */
125   const char *zName,              /* Name assigned to this module */
126   const sqlite3_module *pModule,  /* The definition of the module */
127   void *pAux,                     /* Context pointer for xCreate/xConnect */
128   void (*xDestroy)(void *)        /* Module destructor function */
129 ){
130 #ifdef SQLITE_ENABLE_API_ARMOR
131   if( !sqlite3SafetyCheckOk(db) || zName==0 ) return SQLITE_MISUSE_BKPT;
132 #endif
133   return createModule(db, zName, pModule, pAux, xDestroy);
134 }
135 
136 /*
137 ** External API to drop all virtual-table modules, except those named
138 ** on the azNames list.
139 */
140 int sqlite3_drop_modules(sqlite3 *db, const char** azNames){
141   HashElem *pThis, *pNext;
142 #ifdef SQLITE_ENABLE_API_ARMOR
143   if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
144 #endif
145   for(pThis=sqliteHashFirst(&db->aModule); pThis; pThis=pNext){
146     Module *pMod = (Module*)sqliteHashData(pThis);
147     pNext = sqliteHashNext(pThis);
148     if( azNames ){
149       int ii;
150       for(ii=0; azNames[ii]!=0 && strcmp(azNames[ii],pMod->zName)!=0; ii++){}
151       if( azNames[ii]!=0 ) continue;
152     }
153     createModule(db, pMod->zName, 0, 0, 0);
154   }
155   return SQLITE_OK;
156 }
157 
158 /*
159 ** Decrement the reference count on a Module object.  Destroy the
160 ** module when the reference count reaches zero.
161 */
162 void sqlite3VtabModuleUnref(sqlite3 *db, Module *pMod){
163   assert( pMod->nRefModule>0 );
164   pMod->nRefModule--;
165   if( pMod->nRefModule==0 ){
166     if( pMod->xDestroy ){
167       pMod->xDestroy(pMod->pAux);
168     }
169     assert( pMod->pEpoTab==0 );
170     sqlite3DbFree(db, pMod);
171   }
172 }
173 
174 /*
175 ** Lock the virtual table so that it cannot be disconnected.
176 ** Locks nest.  Every lock should have a corresponding unlock.
177 ** If an unlock is omitted, resources leaks will occur.
178 **
179 ** If a disconnect is attempted while a virtual table is locked,
180 ** the disconnect is deferred until all locks have been removed.
181 */
182 void sqlite3VtabLock(VTable *pVTab){
183   pVTab->nRef++;
184 }
185 
186 
187 /*
188 ** pTab is a pointer to a Table structure representing a virtual-table.
189 ** Return a pointer to the VTable object used by connection db to access
190 ** this virtual-table, if one has been created, or NULL otherwise.
191 */
192 VTable *sqlite3GetVTable(sqlite3 *db, Table *pTab){
193   VTable *pVtab;
194   assert( IsVirtual(pTab) );
195   for(pVtab=pTab->u.vtab.p; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);
196   return pVtab;
197 }
198 
199 /*
200 ** Decrement the ref-count on a virtual table object. When the ref-count
201 ** reaches zero, call the xDisconnect() method to delete the object.
202 */
203 void sqlite3VtabUnlock(VTable *pVTab){
204   sqlite3 *db = pVTab->db;
205 
206   assert( db );
207   assert( pVTab->nRef>0 );
208   assert( db->eOpenState==SQLITE_STATE_OPEN
209        || db->eOpenState==SQLITE_STATE_ZOMBIE );
210 
211   pVTab->nRef--;
212   if( pVTab->nRef==0 ){
213     sqlite3_vtab *p = pVTab->pVtab;
214     sqlite3VtabModuleUnref(pVTab->db, pVTab->pMod);
215     if( p ){
216       p->pModule->xDisconnect(p);
217     }
218     sqlite3DbFree(db, pVTab);
219   }
220 }
221 
222 /*
223 ** Table p is a virtual table. This function moves all elements in the
224 ** p->u.vtab.p list to the sqlite3.pDisconnect lists of their associated
225 ** database connections to be disconnected at the next opportunity.
226 ** Except, if argument db is not NULL, then the entry associated with
227 ** connection db is left in the p->u.vtab.p list.
228 */
229 static VTable *vtabDisconnectAll(sqlite3 *db, Table *p){
230   VTable *pRet = 0;
231   VTable *pVTable;
232 
233   assert( IsVirtual(p) );
234   pVTable = p->u.vtab.p;
235   p->u.vtab.p = 0;
236 
237   /* Assert that the mutex (if any) associated with the BtShared database
238   ** that contains table p is held by the caller. See header comments
239   ** above function sqlite3VtabUnlockList() for an explanation of why
240   ** this makes it safe to access the sqlite3.pDisconnect list of any
241   ** database connection that may have an entry in the p->u.vtab.p list.
242   */
243   assert( db==0 || sqlite3SchemaMutexHeld(db, 0, p->pSchema) );
244 
245   while( pVTable ){
246     sqlite3 *db2 = pVTable->db;
247     VTable *pNext = pVTable->pNext;
248     assert( db2 );
249     if( db2==db ){
250       pRet = pVTable;
251       p->u.vtab.p = pRet;
252       pRet->pNext = 0;
253     }else{
254       pVTable->pNext = db2->pDisconnect;
255       db2->pDisconnect = pVTable;
256     }
257     pVTable = pNext;
258   }
259 
260   assert( !db || pRet );
261   return pRet;
262 }
263 
264 /*
265 ** Table *p is a virtual table. This function removes the VTable object
266 ** for table *p associated with database connection db from the linked
267 ** list in p->pVTab. It also decrements the VTable ref count. This is
268 ** used when closing database connection db to free all of its VTable
269 ** objects without disturbing the rest of the Schema object (which may
270 ** be being used by other shared-cache connections).
271 */
272 void sqlite3VtabDisconnect(sqlite3 *db, Table *p){
273   VTable **ppVTab;
274 
275   assert( IsVirtual(p) );
276   assert( sqlite3BtreeHoldsAllMutexes(db) );
277   assert( sqlite3_mutex_held(db->mutex) );
278 
279   for(ppVTab=&p->u.vtab.p; *ppVTab; ppVTab=&(*ppVTab)->pNext){
280     if( (*ppVTab)->db==db  ){
281       VTable *pVTab = *ppVTab;
282       *ppVTab = pVTab->pNext;
283       sqlite3VtabUnlock(pVTab);
284       break;
285     }
286   }
287 }
288 
289 
290 /*
291 ** Disconnect all the virtual table objects in the sqlite3.pDisconnect list.
292 **
293 ** This function may only be called when the mutexes associated with all
294 ** shared b-tree databases opened using connection db are held by the
295 ** caller. This is done to protect the sqlite3.pDisconnect list. The
296 ** sqlite3.pDisconnect list is accessed only as follows:
297 **
298 **   1) By this function. In this case, all BtShared mutexes and the mutex
299 **      associated with the database handle itself must be held.
300 **
301 **   2) By function vtabDisconnectAll(), when it adds a VTable entry to
302 **      the sqlite3.pDisconnect list. In this case either the BtShared mutex
303 **      associated with the database the virtual table is stored in is held
304 **      or, if the virtual table is stored in a non-sharable database, then
305 **      the database handle mutex is held.
306 **
307 ** As a result, a sqlite3.pDisconnect cannot be accessed simultaneously
308 ** by multiple threads. It is thread-safe.
309 */
310 void sqlite3VtabUnlockList(sqlite3 *db){
311   VTable *p = db->pDisconnect;
312 
313   assert( sqlite3BtreeHoldsAllMutexes(db) );
314   assert( sqlite3_mutex_held(db->mutex) );
315 
316   if( p ){
317     db->pDisconnect = 0;
318     sqlite3ExpirePreparedStatements(db, 0);
319     do {
320       VTable *pNext = p->pNext;
321       sqlite3VtabUnlock(p);
322       p = pNext;
323     }while( p );
324   }
325 }
326 
327 /*
328 ** Clear any and all virtual-table information from the Table record.
329 ** This routine is called, for example, just before deleting the Table
330 ** record.
331 **
332 ** Since it is a virtual-table, the Table structure contains a pointer
333 ** to the head of a linked list of VTable structures. Each VTable
334 ** structure is associated with a single sqlite3* user of the schema.
335 ** The reference count of the VTable structure associated with database
336 ** connection db is decremented immediately (which may lead to the
337 ** structure being xDisconnected and free). Any other VTable structures
338 ** in the list are moved to the sqlite3.pDisconnect list of the associated
339 ** database connection.
340 */
341 void sqlite3VtabClear(sqlite3 *db, Table *p){
342   assert( IsVirtual(p) );
343   if( !db || db->pnBytesFreed==0 ) vtabDisconnectAll(0, p);
344   if( p->u.vtab.azArg ){
345     int i;
346     for(i=0; i<p->u.vtab.nArg; i++){
347       if( i!=1 ) sqlite3DbFree(db, p->u.vtab.azArg[i]);
348     }
349     sqlite3DbFree(db, p->u.vtab.azArg);
350   }
351 }
352 
353 /*
354 ** Add a new module argument to pTable->u.vtab.azArg[].
355 ** The string is not copied - the pointer is stored.  The
356 ** string will be freed automatically when the table is
357 ** deleted.
358 */
359 static void addModuleArgument(Parse *pParse, Table *pTable, char *zArg){
360   sqlite3_int64 nBytes;
361   char **azModuleArg;
362   sqlite3 *db = pParse->db;
363 
364   assert( IsVirtual(pTable) );
365   nBytes = sizeof(char *)*(2+pTable->u.vtab.nArg);
366   if( pTable->u.vtab.nArg+3>=db->aLimit[SQLITE_LIMIT_COLUMN] ){
367     sqlite3ErrorMsg(pParse, "too many columns on %s", pTable->zName);
368   }
369   azModuleArg = sqlite3DbRealloc(db, pTable->u.vtab.azArg, nBytes);
370   if( azModuleArg==0 ){
371     sqlite3DbFree(db, zArg);
372   }else{
373     int i = pTable->u.vtab.nArg++;
374     azModuleArg[i] = zArg;
375     azModuleArg[i+1] = 0;
376     pTable->u.vtab.azArg = azModuleArg;
377   }
378 }
379 
380 /*
381 ** The parser calls this routine when it first sees a CREATE VIRTUAL TABLE
382 ** statement.  The module name has been parsed, but the optional list
383 ** of parameters that follow the module name are still pending.
384 */
385 void sqlite3VtabBeginParse(
386   Parse *pParse,        /* Parsing context */
387   Token *pName1,        /* Name of new table, or database name */
388   Token *pName2,        /* Name of new table or NULL */
389   Token *pModuleName,   /* Name of the module for the virtual table */
390   int ifNotExists       /* No error if the table already exists */
391 ){
392   Table *pTable;        /* The new virtual table */
393   sqlite3 *db;          /* Database connection */
394 
395   sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, ifNotExists);
396   pTable = pParse->pNewTable;
397   if( pTable==0 ) return;
398   assert( 0==pTable->pIndex );
399   pTable->eTabType = TABTYP_VTAB;
400 
401   db = pParse->db;
402 
403   assert( pTable->u.vtab.nArg==0 );
404   addModuleArgument(pParse, pTable, sqlite3NameFromToken(db, pModuleName));
405   addModuleArgument(pParse, pTable, 0);
406   addModuleArgument(pParse, pTable, sqlite3DbStrDup(db, pTable->zName));
407   assert( (pParse->sNameToken.z==pName2->z && pName2->z!=0)
408        || (pParse->sNameToken.z==pName1->z && pName2->z==0)
409   );
410   pParse->sNameToken.n = (int)(
411       &pModuleName->z[pModuleName->n] - pParse->sNameToken.z
412   );
413 
414 #ifndef SQLITE_OMIT_AUTHORIZATION
415   /* Creating a virtual table invokes the authorization callback twice.
416   ** The first invocation, to obtain permission to INSERT a row into the
417   ** sqlite_schema table, has already been made by sqlite3StartTable().
418   ** The second call, to obtain permission to create the table, is made now.
419   */
420   if( pTable->u.vtab.azArg ){
421     int iDb = sqlite3SchemaToIndex(db, pTable->pSchema);
422     assert( iDb>=0 ); /* The database the table is being created in */
423     sqlite3AuthCheck(pParse, SQLITE_CREATE_VTABLE, pTable->zName,
424             pTable->u.vtab.azArg[0], pParse->db->aDb[iDb].zDbSName);
425   }
426 #endif
427 }
428 
429 /*
430 ** This routine takes the module argument that has been accumulating
431 ** in pParse->zArg[] and appends it to the list of arguments on the
432 ** virtual table currently under construction in pParse->pTable.
433 */
434 static void addArgumentToVtab(Parse *pParse){
435   if( pParse->sArg.z && pParse->pNewTable ){
436     const char *z = (const char*)pParse->sArg.z;
437     int n = pParse->sArg.n;
438     sqlite3 *db = pParse->db;
439     addModuleArgument(pParse, pParse->pNewTable, sqlite3DbStrNDup(db, z, n));
440   }
441 }
442 
443 /*
444 ** The parser calls this routine after the CREATE VIRTUAL TABLE statement
445 ** has been completely parsed.
446 */
447 void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){
448   Table *pTab = pParse->pNewTable;  /* The table being constructed */
449   sqlite3 *db = pParse->db;         /* The database connection */
450 
451   if( pTab==0 ) return;
452   assert( IsVirtual(pTab) );
453   addArgumentToVtab(pParse);
454   pParse->sArg.z = 0;
455   if( pTab->u.vtab.nArg<1 ) return;
456 
457   /* If the CREATE VIRTUAL TABLE statement is being entered for the
458   ** first time (in other words if the virtual table is actually being
459   ** created now instead of just being read out of sqlite_schema) then
460   ** do additional initialization work and store the statement text
461   ** in the sqlite_schema table.
462   */
463   if( !db->init.busy ){
464     char *zStmt;
465     char *zWhere;
466     int iDb;
467     int iReg;
468     Vdbe *v;
469 
470     sqlite3MayAbort(pParse);
471 
472     /* Compute the complete text of the CREATE VIRTUAL TABLE statement */
473     if( pEnd ){
474       pParse->sNameToken.n = (int)(pEnd->z - pParse->sNameToken.z) + pEnd->n;
475     }
476     zStmt = sqlite3MPrintf(db, "CREATE VIRTUAL TABLE %T", &pParse->sNameToken);
477 
478     /* A slot for the record has already been allocated in the
479     ** schema table.  We just need to update that slot with all
480     ** the information we've collected.
481     **
482     ** The VM register number pParse->regRowid holds the rowid of an
483     ** entry in the sqlite_schema table tht was created for this vtab
484     ** by sqlite3StartTable().
485     */
486     iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
487     sqlite3NestedParse(pParse,
488       "UPDATE %Q." DFLT_SCHEMA_TABLE " "
489          "SET type='table', name=%Q, tbl_name=%Q, rootpage=0, sql=%Q "
490        "WHERE rowid=#%d",
491       db->aDb[iDb].zDbSName,
492       pTab->zName,
493       pTab->zName,
494       zStmt,
495       pParse->regRowid
496     );
497     v = sqlite3GetVdbe(pParse);
498     sqlite3ChangeCookie(pParse, iDb);
499 
500     sqlite3VdbeAddOp0(v, OP_Expire);
501     zWhere = sqlite3MPrintf(db, "name=%Q AND sql=%Q", pTab->zName, zStmt);
502     sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere, 0);
503     sqlite3DbFree(db, zStmt);
504 
505     iReg = ++pParse->nMem;
506     sqlite3VdbeLoadString(v, iReg, pTab->zName);
507     sqlite3VdbeAddOp2(v, OP_VCreate, iDb, iReg);
508   }else{
509     /* If we are rereading the sqlite_schema table create the in-memory
510     ** record of the table. */
511     Table *pOld;
512     Schema *pSchema = pTab->pSchema;
513     const char *zName = pTab->zName;
514     assert( zName!=0 );
515     sqlite3MarkAllShadowTablesOf(db, pTab);
516     pOld = sqlite3HashInsert(&pSchema->tblHash, zName, pTab);
517     if( pOld ){
518       sqlite3OomFault(db);
519       assert( pTab==pOld );  /* Malloc must have failed inside HashInsert() */
520       return;
521     }
522     pParse->pNewTable = 0;
523   }
524 }
525 
526 /*
527 ** The parser calls this routine when it sees the first token
528 ** of an argument to the module name in a CREATE VIRTUAL TABLE statement.
529 */
530 void sqlite3VtabArgInit(Parse *pParse){
531   addArgumentToVtab(pParse);
532   pParse->sArg.z = 0;
533   pParse->sArg.n = 0;
534 }
535 
536 /*
537 ** The parser calls this routine for each token after the first token
538 ** in an argument to the module name in a CREATE VIRTUAL TABLE statement.
539 */
540 void sqlite3VtabArgExtend(Parse *pParse, Token *p){
541   Token *pArg = &pParse->sArg;
542   if( pArg->z==0 ){
543     pArg->z = p->z;
544     pArg->n = p->n;
545   }else{
546     assert(pArg->z <= p->z);
547     pArg->n = (int)(&p->z[p->n] - pArg->z);
548   }
549 }
550 
551 /*
552 ** Invoke a virtual table constructor (either xCreate or xConnect). The
553 ** pointer to the function to invoke is passed as the fourth parameter
554 ** to this procedure.
555 */
556 static int vtabCallConstructor(
557   sqlite3 *db,
558   Table *pTab,
559   Module *pMod,
560   int (*xConstruct)(sqlite3*,void*,int,const char*const*,sqlite3_vtab**,char**),
561   char **pzErr
562 ){
563   VtabCtx sCtx;
564   VTable *pVTable;
565   int rc;
566   const char *const*azArg;
567   int nArg = pTab->u.vtab.nArg;
568   char *zErr = 0;
569   char *zModuleName;
570   int iDb;
571   VtabCtx *pCtx;
572 
573   assert( IsVirtual(pTab) );
574   azArg = (const char *const*)pTab->u.vtab.azArg;
575 
576   /* Check that the virtual-table is not already being initialized */
577   for(pCtx=db->pVtabCtx; pCtx; pCtx=pCtx->pPrior){
578     if( pCtx->pTab==pTab ){
579       *pzErr = sqlite3MPrintf(db,
580           "vtable constructor called recursively: %s", pTab->zName
581       );
582       return SQLITE_LOCKED;
583     }
584   }
585 
586   zModuleName = sqlite3DbStrDup(db, pTab->zName);
587   if( !zModuleName ){
588     return SQLITE_NOMEM_BKPT;
589   }
590 
591   pVTable = sqlite3MallocZero(sizeof(VTable));
592   if( !pVTable ){
593     sqlite3OomFault(db);
594     sqlite3DbFree(db, zModuleName);
595     return SQLITE_NOMEM_BKPT;
596   }
597   pVTable->db = db;
598   pVTable->pMod = pMod;
599   pVTable->eVtabRisk = SQLITE_VTABRISK_Normal;
600 
601   iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
602   pTab->u.vtab.azArg[1] = db->aDb[iDb].zDbSName;
603 
604   /* Invoke the virtual table constructor */
605   assert( &db->pVtabCtx );
606   assert( xConstruct );
607   sCtx.pTab = pTab;
608   sCtx.pVTable = pVTable;
609   sCtx.pPrior = db->pVtabCtx;
610   sCtx.bDeclared = 0;
611   db->pVtabCtx = &sCtx;
612   rc = xConstruct(db, pMod->pAux, nArg, azArg, &pVTable->pVtab, &zErr);
613   db->pVtabCtx = sCtx.pPrior;
614   if( rc==SQLITE_NOMEM ) sqlite3OomFault(db);
615   assert( sCtx.pTab==pTab );
616 
617   if( SQLITE_OK!=rc ){
618     if( zErr==0 ){
619       *pzErr = sqlite3MPrintf(db, "vtable constructor failed: %s", zModuleName);
620     }else {
621       *pzErr = sqlite3MPrintf(db, "%s", zErr);
622       sqlite3_free(zErr);
623     }
624     sqlite3DbFree(db, pVTable);
625   }else if( ALWAYS(pVTable->pVtab) ){
626     /* Justification of ALWAYS():  A correct vtab constructor must allocate
627     ** the sqlite3_vtab object if successful.  */
628     memset(pVTable->pVtab, 0, sizeof(pVTable->pVtab[0]));
629     pVTable->pVtab->pModule = pMod->pModule;
630     pMod->nRefModule++;
631     pVTable->nRef = 1;
632     if( sCtx.bDeclared==0 ){
633       const char *zFormat = "vtable constructor did not declare schema: %s";
634       *pzErr = sqlite3MPrintf(db, zFormat, pTab->zName);
635       sqlite3VtabUnlock(pVTable);
636       rc = SQLITE_ERROR;
637     }else{
638       int iCol;
639       u16 oooHidden = 0;
640       /* If everything went according to plan, link the new VTable structure
641       ** into the linked list headed by pTab->u.vtab.p. Then loop through the
642       ** columns of the table to see if any of them contain the token "hidden".
643       ** If so, set the Column COLFLAG_HIDDEN flag and remove the token from
644       ** the type string.  */
645       pVTable->pNext = pTab->u.vtab.p;
646       pTab->u.vtab.p = pVTable;
647 
648       for(iCol=0; iCol<pTab->nCol; iCol++){
649         char *zType = sqlite3ColumnType(&pTab->aCol[iCol], "");
650         int nType;
651         int i = 0;
652         nType = sqlite3Strlen30(zType);
653         for(i=0; i<nType; i++){
654           if( 0==sqlite3StrNICmp("hidden", &zType[i], 6)
655            && (i==0 || zType[i-1]==' ')
656            && (zType[i+6]=='\0' || zType[i+6]==' ')
657           ){
658             break;
659           }
660         }
661         if( i<nType ){
662           int j;
663           int nDel = 6 + (zType[i+6] ? 1 : 0);
664           for(j=i; (j+nDel)<=nType; j++){
665             zType[j] = zType[j+nDel];
666           }
667           if( zType[i]=='\0' && i>0 ){
668             assert(zType[i-1]==' ');
669             zType[i-1] = '\0';
670           }
671           pTab->aCol[iCol].colFlags |= COLFLAG_HIDDEN;
672           pTab->tabFlags |= TF_HasHidden;
673           oooHidden = TF_OOOHidden;
674         }else{
675           pTab->tabFlags |= oooHidden;
676         }
677       }
678     }
679   }
680 
681   sqlite3DbFree(db, zModuleName);
682   return rc;
683 }
684 
685 /*
686 ** This function is invoked by the parser to call the xConnect() method
687 ** of the virtual table pTab. If an error occurs, an error code is returned
688 ** and an error left in pParse.
689 **
690 ** This call is a no-op if table pTab is not a virtual table.
691 */
692 int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
693   sqlite3 *db = pParse->db;
694   const char *zMod;
695   Module *pMod;
696   int rc;
697 
698   assert( pTab );
699   if( !IsVirtual(pTab) || sqlite3GetVTable(db, pTab) ){
700     return SQLITE_OK;
701   }
702 
703   /* Locate the required virtual table module */
704   zMod = pTab->u.vtab.azArg[0];
705   pMod = (Module*)sqlite3HashFind(&db->aModule, zMod);
706 
707   if( !pMod ){
708     const char *zModule = pTab->u.vtab.azArg[0];
709     sqlite3ErrorMsg(pParse, "no such module: %s", zModule);
710     rc = SQLITE_ERROR;
711   }else{
712     char *zErr = 0;
713     rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xConnect, &zErr);
714     if( rc!=SQLITE_OK ){
715       sqlite3ErrorMsg(pParse, "%s", zErr);
716       pParse->rc = rc;
717     }
718     sqlite3DbFree(db, zErr);
719   }
720 
721   return rc;
722 }
723 /*
724 ** Grow the db->aVTrans[] array so that there is room for at least one
725 ** more v-table. Return SQLITE_NOMEM if a malloc fails, or SQLITE_OK otherwise.
726 */
727 static int growVTrans(sqlite3 *db){
728   const int ARRAY_INCR = 5;
729 
730   /* Grow the sqlite3.aVTrans array if required */
731   if( (db->nVTrans%ARRAY_INCR)==0 ){
732     VTable **aVTrans;
733     sqlite3_int64 nBytes = sizeof(sqlite3_vtab*)*
734                                  ((sqlite3_int64)db->nVTrans + ARRAY_INCR);
735     aVTrans = sqlite3DbRealloc(db, (void *)db->aVTrans, nBytes);
736     if( !aVTrans ){
737       return SQLITE_NOMEM_BKPT;
738     }
739     memset(&aVTrans[db->nVTrans], 0, sizeof(sqlite3_vtab *)*ARRAY_INCR);
740     db->aVTrans = aVTrans;
741   }
742 
743   return SQLITE_OK;
744 }
745 
746 /*
747 ** Add the virtual table pVTab to the array sqlite3.aVTrans[]. Space should
748 ** have already been reserved using growVTrans().
749 */
750 static void addToVTrans(sqlite3 *db, VTable *pVTab){
751   /* Add pVtab to the end of sqlite3.aVTrans */
752   db->aVTrans[db->nVTrans++] = pVTab;
753   sqlite3VtabLock(pVTab);
754 }
755 
756 /*
757 ** This function is invoked by the vdbe to call the xCreate method
758 ** of the virtual table named zTab in database iDb.
759 **
760 ** If an error occurs, *pzErr is set to point to an English language
761 ** description of the error and an SQLITE_XXX error code is returned.
762 ** In this case the caller must call sqlite3DbFree(db, ) on *pzErr.
763 */
764 int sqlite3VtabCallCreate(sqlite3 *db, int iDb, const char *zTab, char **pzErr){
765   int rc = SQLITE_OK;
766   Table *pTab;
767   Module *pMod;
768   const char *zMod;
769 
770   pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zDbSName);
771   assert( pTab && IsVirtual(pTab) && !pTab->u.vtab.p );
772 
773   /* Locate the required virtual table module */
774   zMod = pTab->u.vtab.azArg[0];
775   pMod = (Module*)sqlite3HashFind(&db->aModule, zMod);
776 
777   /* If the module has been registered and includes a Create method,
778   ** invoke it now. If the module has not been registered, return an
779   ** error. Otherwise, do nothing.
780   */
781   if( pMod==0 || pMod->pModule->xCreate==0 || pMod->pModule->xDestroy==0 ){
782     *pzErr = sqlite3MPrintf(db, "no such module: %s", zMod);
783     rc = SQLITE_ERROR;
784   }else{
785     rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xCreate, pzErr);
786   }
787 
788   /* Justification of ALWAYS():  The xConstructor method is required to
789   ** create a valid sqlite3_vtab if it returns SQLITE_OK. */
790   if( rc==SQLITE_OK && ALWAYS(sqlite3GetVTable(db, pTab)) ){
791     rc = growVTrans(db);
792     if( rc==SQLITE_OK ){
793       addToVTrans(db, sqlite3GetVTable(db, pTab));
794     }
795   }
796 
797   return rc;
798 }
799 
800 /*
801 ** This function is used to set the schema of a virtual table.  It is only
802 ** valid to call this function from within the xCreate() or xConnect() of a
803 ** virtual table module.
804 */
805 int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
806   VtabCtx *pCtx;
807   int rc = SQLITE_OK;
808   Table *pTab;
809   char *zErr = 0;
810   Parse sParse;
811   int initBusy;
812 
813 #ifdef SQLITE_ENABLE_API_ARMOR
814   if( !sqlite3SafetyCheckOk(db) || zCreateTable==0 ){
815     return SQLITE_MISUSE_BKPT;
816   }
817 #endif
818   sqlite3_mutex_enter(db->mutex);
819   pCtx = db->pVtabCtx;
820   if( !pCtx || pCtx->bDeclared ){
821     sqlite3Error(db, SQLITE_MISUSE);
822     sqlite3_mutex_leave(db->mutex);
823     return SQLITE_MISUSE_BKPT;
824   }
825   pTab = pCtx->pTab;
826   assert( IsVirtual(pTab) );
827 
828   memset(&sParse, 0, sizeof(sParse));
829   sParse.eParseMode = PARSE_MODE_DECLARE_VTAB;
830   sParse.db = db;
831   /* We should never be able to reach this point while loading the
832   ** schema.  Nevertheless, defend against that (turn off db->init.busy)
833   ** in case a bug arises. */
834   assert( db->init.busy==0 );
835   initBusy = db->init.busy;
836   db->init.busy = 0;
837   sParse.nQueryLoop = 1;
838   if( SQLITE_OK==sqlite3RunParser(&sParse, zCreateTable, &zErr)
839    && sParse.pNewTable
840    && !db->mallocFailed
841    && IsOrdinaryTable(sParse.pNewTable)
842   ){
843     if( !pTab->aCol ){
844       Table *pNew = sParse.pNewTable;
845       Index *pIdx;
846       pTab->aCol = pNew->aCol;
847       sqlite3ExprListDelete(db, pNew->u.tab.pDfltList);
848       pTab->nNVCol = pTab->nCol = pNew->nCol;
849       pTab->tabFlags |= pNew->tabFlags & (TF_WithoutRowid|TF_NoVisibleRowid);
850       pNew->nCol = 0;
851       pNew->aCol = 0;
852       assert( pTab->pIndex==0 );
853       assert( HasRowid(pNew) || sqlite3PrimaryKeyIndex(pNew)!=0 );
854       if( !HasRowid(pNew)
855        && pCtx->pVTable->pMod->pModule->xUpdate!=0
856        && sqlite3PrimaryKeyIndex(pNew)->nKeyCol!=1
857       ){
858         /* WITHOUT ROWID virtual tables must either be read-only (xUpdate==0)
859         ** or else must have a single-column PRIMARY KEY */
860         rc = SQLITE_ERROR;
861       }
862       pIdx = pNew->pIndex;
863       if( pIdx ){
864         assert( pIdx->pNext==0 );
865         pTab->pIndex = pIdx;
866         pNew->pIndex = 0;
867         pIdx->pTable = pTab;
868       }
869     }
870     pCtx->bDeclared = 1;
871   }else{
872     sqlite3ErrorWithMsg(db, SQLITE_ERROR, (zErr ? "%s" : 0), zErr);
873     sqlite3DbFree(db, zErr);
874     rc = SQLITE_ERROR;
875   }
876   sParse.eParseMode = PARSE_MODE_NORMAL;
877 
878   if( sParse.pVdbe ){
879     sqlite3VdbeFinalize(sParse.pVdbe);
880   }
881   sqlite3DeleteTable(db, sParse.pNewTable);
882   sqlite3ParserReset(&sParse);
883   db->init.busy = initBusy;
884 
885   assert( (rc&0xff)==rc );
886   rc = sqlite3ApiExit(db, rc);
887   sqlite3_mutex_leave(db->mutex);
888   return rc;
889 }
890 
891 /*
892 ** This function is invoked by the vdbe to call the xDestroy method
893 ** of the virtual table named zTab in database iDb. This occurs
894 ** when a DROP TABLE is mentioned.
895 **
896 ** This call is a no-op if zTab is not a virtual table.
897 */
898 int sqlite3VtabCallDestroy(sqlite3 *db, int iDb, const char *zTab){
899   int rc = SQLITE_OK;
900   Table *pTab;
901 
902   pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zDbSName);
903   if( pTab!=0 && ALWAYS(IsVirtual(pTab)) && ALWAYS(pTab->u.vtab.p!=0) ){
904     VTable *p;
905     int (*xDestroy)(sqlite3_vtab *);
906     for(p=pTab->u.vtab.p; p; p=p->pNext){
907       assert( p->pVtab );
908       if( p->pVtab->nRef>0 ){
909         return SQLITE_LOCKED;
910       }
911     }
912     p = vtabDisconnectAll(db, pTab);
913     xDestroy = p->pMod->pModule->xDestroy;
914     if( xDestroy==0 ) xDestroy = p->pMod->pModule->xDisconnect;
915     assert( xDestroy!=0 );
916     pTab->nTabRef++;
917     rc = xDestroy(p->pVtab);
918     /* Remove the sqlite3_vtab* from the aVTrans[] array, if applicable */
919     if( rc==SQLITE_OK ){
920       assert( pTab->u.vtab.p==p && p->pNext==0 );
921       p->pVtab = 0;
922       pTab->u.vtab.p = 0;
923       sqlite3VtabUnlock(p);
924     }
925     sqlite3DeleteTable(db, pTab);
926   }
927 
928   return rc;
929 }
930 
931 /*
932 ** This function invokes either the xRollback or xCommit method
933 ** of each of the virtual tables in the sqlite3.aVTrans array. The method
934 ** called is identified by the second argument, "offset", which is
935 ** the offset of the method to call in the sqlite3_module structure.
936 **
937 ** The array is cleared after invoking the callbacks.
938 */
939 static void callFinaliser(sqlite3 *db, int offset){
940   int i;
941   if( db->aVTrans ){
942     VTable **aVTrans = db->aVTrans;
943     db->aVTrans = 0;
944     for(i=0; i<db->nVTrans; i++){
945       VTable *pVTab = aVTrans[i];
946       sqlite3_vtab *p = pVTab->pVtab;
947       if( p ){
948         int (*x)(sqlite3_vtab *);
949         x = *(int (**)(sqlite3_vtab *))((char *)p->pModule + offset);
950         if( x ) x(p);
951       }
952       pVTab->iSavepoint = 0;
953       sqlite3VtabUnlock(pVTab);
954     }
955     sqlite3DbFree(db, aVTrans);
956     db->nVTrans = 0;
957   }
958 }
959 
960 /*
961 ** Invoke the xSync method of all virtual tables in the sqlite3.aVTrans
962 ** array. Return the error code for the first error that occurs, or
963 ** SQLITE_OK if all xSync operations are successful.
964 **
965 ** If an error message is available, leave it in p->zErrMsg.
966 */
967 int sqlite3VtabSync(sqlite3 *db, Vdbe *p){
968   int i;
969   int rc = SQLITE_OK;
970   VTable **aVTrans = db->aVTrans;
971 
972   db->aVTrans = 0;
973   for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
974     int (*x)(sqlite3_vtab *);
975     sqlite3_vtab *pVtab = aVTrans[i]->pVtab;
976     if( pVtab && (x = pVtab->pModule->xSync)!=0 ){
977       rc = x(pVtab);
978       sqlite3VtabImportErrmsg(p, pVtab);
979     }
980   }
981   db->aVTrans = aVTrans;
982   return rc;
983 }
984 
985 /*
986 ** Invoke the xRollback method of all virtual tables in the
987 ** sqlite3.aVTrans array. Then clear the array itself.
988 */
989 int sqlite3VtabRollback(sqlite3 *db){
990   callFinaliser(db, offsetof(sqlite3_module,xRollback));
991   return SQLITE_OK;
992 }
993 
994 /*
995 ** Invoke the xCommit method of all virtual tables in the
996 ** sqlite3.aVTrans array. Then clear the array itself.
997 */
998 int sqlite3VtabCommit(sqlite3 *db){
999   callFinaliser(db, offsetof(sqlite3_module,xCommit));
1000   return SQLITE_OK;
1001 }
1002 
1003 /*
1004 ** If the virtual table pVtab supports the transaction interface
1005 ** (xBegin/xRollback/xCommit and optionally xSync) and a transaction is
1006 ** not currently open, invoke the xBegin method now.
1007 **
1008 ** If the xBegin call is successful, place the sqlite3_vtab pointer
1009 ** in the sqlite3.aVTrans array.
1010 */
1011 int sqlite3VtabBegin(sqlite3 *db, VTable *pVTab){
1012   int rc = SQLITE_OK;
1013   const sqlite3_module *pModule;
1014 
1015   /* Special case: If db->aVTrans is NULL and db->nVTrans is greater
1016   ** than zero, then this function is being called from within a
1017   ** virtual module xSync() callback. It is illegal to write to
1018   ** virtual module tables in this case, so return SQLITE_LOCKED.
1019   */
1020   if( sqlite3VtabInSync(db) ){
1021     return SQLITE_LOCKED;
1022   }
1023   if( !pVTab ){
1024     return SQLITE_OK;
1025   }
1026   pModule = pVTab->pVtab->pModule;
1027 
1028   if( pModule->xBegin ){
1029     int i;
1030 
1031     /* If pVtab is already in the aVTrans array, return early */
1032     for(i=0; i<db->nVTrans; i++){
1033       if( db->aVTrans[i]==pVTab ){
1034         return SQLITE_OK;
1035       }
1036     }
1037 
1038     /* Invoke the xBegin method. If successful, add the vtab to the
1039     ** sqlite3.aVTrans[] array. */
1040     rc = growVTrans(db);
1041     if( rc==SQLITE_OK ){
1042       rc = pModule->xBegin(pVTab->pVtab);
1043       if( rc==SQLITE_OK ){
1044         int iSvpt = db->nStatement + db->nSavepoint;
1045         addToVTrans(db, pVTab);
1046         if( iSvpt && pModule->xSavepoint ){
1047           pVTab->iSavepoint = iSvpt;
1048           rc = pModule->xSavepoint(pVTab->pVtab, iSvpt-1);
1049         }
1050       }
1051     }
1052   }
1053   return rc;
1054 }
1055 
1056 /*
1057 ** Invoke either the xSavepoint, xRollbackTo or xRelease method of all
1058 ** virtual tables that currently have an open transaction. Pass iSavepoint
1059 ** as the second argument to the virtual table method invoked.
1060 **
1061 ** If op is SAVEPOINT_BEGIN, the xSavepoint method is invoked. If it is
1062 ** SAVEPOINT_ROLLBACK, the xRollbackTo method. Otherwise, if op is
1063 ** SAVEPOINT_RELEASE, then the xRelease method of each virtual table with
1064 ** an open transaction is invoked.
1065 **
1066 ** If any virtual table method returns an error code other than SQLITE_OK,
1067 ** processing is abandoned and the error returned to the caller of this
1068 ** function immediately. If all calls to virtual table methods are successful,
1069 ** SQLITE_OK is returned.
1070 */
1071 int sqlite3VtabSavepoint(sqlite3 *db, int op, int iSavepoint){
1072   int rc = SQLITE_OK;
1073 
1074   assert( op==SAVEPOINT_RELEASE||op==SAVEPOINT_ROLLBACK||op==SAVEPOINT_BEGIN );
1075   assert( iSavepoint>=-1 );
1076   if( db->aVTrans ){
1077     int i;
1078     for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
1079       VTable *pVTab = db->aVTrans[i];
1080       const sqlite3_module *pMod = pVTab->pMod->pModule;
1081       if( pVTab->pVtab && pMod->iVersion>=2 ){
1082         int (*xMethod)(sqlite3_vtab *, int);
1083         sqlite3VtabLock(pVTab);
1084         switch( op ){
1085           case SAVEPOINT_BEGIN:
1086             xMethod = pMod->xSavepoint;
1087             pVTab->iSavepoint = iSavepoint+1;
1088             break;
1089           case SAVEPOINT_ROLLBACK:
1090             xMethod = pMod->xRollbackTo;
1091             break;
1092           default:
1093             xMethod = pMod->xRelease;
1094             break;
1095         }
1096         if( xMethod && pVTab->iSavepoint>iSavepoint ){
1097           rc = xMethod(pVTab->pVtab, iSavepoint);
1098         }
1099         sqlite3VtabUnlock(pVTab);
1100       }
1101     }
1102   }
1103   return rc;
1104 }
1105 
1106 /*
1107 ** The first parameter (pDef) is a function implementation.  The
1108 ** second parameter (pExpr) is the first argument to this function.
1109 ** If pExpr is a column in a virtual table, then let the virtual
1110 ** table implementation have an opportunity to overload the function.
1111 **
1112 ** This routine is used to allow virtual table implementations to
1113 ** overload MATCH, LIKE, GLOB, and REGEXP operators.
1114 **
1115 ** Return either the pDef argument (indicating no change) or a
1116 ** new FuncDef structure that is marked as ephemeral using the
1117 ** SQLITE_FUNC_EPHEM flag.
1118 */
1119 FuncDef *sqlite3VtabOverloadFunction(
1120   sqlite3 *db,    /* Database connection for reporting malloc problems */
1121   FuncDef *pDef,  /* Function to possibly overload */
1122   int nArg,       /* Number of arguments to the function */
1123   Expr *pExpr     /* First argument to the function */
1124 ){
1125   Table *pTab;
1126   sqlite3_vtab *pVtab;
1127   sqlite3_module *pMod;
1128   void (*xSFunc)(sqlite3_context*,int,sqlite3_value**) = 0;
1129   void *pArg = 0;
1130   FuncDef *pNew;
1131   int rc = 0;
1132 
1133   /* Check to see the left operand is a column in a virtual table */
1134   if( NEVER(pExpr==0) ) return pDef;
1135   if( pExpr->op!=TK_COLUMN ) return pDef;
1136   assert( ExprUseYTab(pExpr) );
1137   pTab = pExpr->y.pTab;
1138   if( pTab==0 ) return pDef;
1139   if( !IsVirtual(pTab) ) return pDef;
1140   pVtab = sqlite3GetVTable(db, pTab)->pVtab;
1141   assert( pVtab!=0 );
1142   assert( pVtab->pModule!=0 );
1143   pMod = (sqlite3_module *)pVtab->pModule;
1144   if( pMod->xFindFunction==0 ) return pDef;
1145 
1146   /* Call the xFindFunction method on the virtual table implementation
1147   ** to see if the implementation wants to overload this function.
1148   **
1149   ** Though undocumented, we have historically always invoked xFindFunction
1150   ** with an all lower-case function name.  Continue in this tradition to
1151   ** avoid any chance of an incompatibility.
1152   */
1153 #ifdef SQLITE_DEBUG
1154   {
1155     int i;
1156     for(i=0; pDef->zName[i]; i++){
1157       unsigned char x = (unsigned char)pDef->zName[i];
1158       assert( x==sqlite3UpperToLower[x] );
1159     }
1160   }
1161 #endif
1162   rc = pMod->xFindFunction(pVtab, nArg, pDef->zName, &xSFunc, &pArg);
1163   if( rc==0 ){
1164     return pDef;
1165   }
1166 
1167   /* Create a new ephemeral function definition for the overloaded
1168   ** function */
1169   pNew = sqlite3DbMallocZero(db, sizeof(*pNew)
1170                              + sqlite3Strlen30(pDef->zName) + 1);
1171   if( pNew==0 ){
1172     return pDef;
1173   }
1174   *pNew = *pDef;
1175   pNew->zName = (const char*)&pNew[1];
1176   memcpy((char*)&pNew[1], pDef->zName, sqlite3Strlen30(pDef->zName)+1);
1177   pNew->xSFunc = xSFunc;
1178   pNew->pUserData = pArg;
1179   pNew->funcFlags |= SQLITE_FUNC_EPHEM;
1180   return pNew;
1181 }
1182 
1183 /*
1184 ** Make sure virtual table pTab is contained in the pParse->apVirtualLock[]
1185 ** array so that an OP_VBegin will get generated for it.  Add pTab to the
1186 ** array if it is missing.  If pTab is already in the array, this routine
1187 ** is a no-op.
1188 */
1189 void sqlite3VtabMakeWritable(Parse *pParse, Table *pTab){
1190   Parse *pToplevel = sqlite3ParseToplevel(pParse);
1191   int i, n;
1192   Table **apVtabLock;
1193 
1194   assert( IsVirtual(pTab) );
1195   for(i=0; i<pToplevel->nVtabLock; i++){
1196     if( pTab==pToplevel->apVtabLock[i] ) return;
1197   }
1198   n = (pToplevel->nVtabLock+1)*sizeof(pToplevel->apVtabLock[0]);
1199   apVtabLock = sqlite3Realloc(pToplevel->apVtabLock, n);
1200   if( apVtabLock ){
1201     pToplevel->apVtabLock = apVtabLock;
1202     pToplevel->apVtabLock[pToplevel->nVtabLock++] = pTab;
1203   }else{
1204     sqlite3OomFault(pToplevel->db);
1205   }
1206 }
1207 
1208 /*
1209 ** Check to see if virtual table module pMod can be have an eponymous
1210 ** virtual table instance.  If it can, create one if one does not already
1211 ** exist. Return non-zero if either the eponymous virtual table instance
1212 ** exists when this routine returns or if an attempt to create it failed
1213 ** and an error message was left in pParse.
1214 **
1215 ** An eponymous virtual table instance is one that is named after its
1216 ** module, and more importantly, does not require a CREATE VIRTUAL TABLE
1217 ** statement in order to come into existance.  Eponymous virtual table
1218 ** instances always exist.  They cannot be DROP-ed.
1219 **
1220 ** Any virtual table module for which xConnect and xCreate are the same
1221 ** method can have an eponymous virtual table instance.
1222 */
1223 int sqlite3VtabEponymousTableInit(Parse *pParse, Module *pMod){
1224   const sqlite3_module *pModule = pMod->pModule;
1225   Table *pTab;
1226   char *zErr = 0;
1227   int rc;
1228   sqlite3 *db = pParse->db;
1229   if( pMod->pEpoTab ) return 1;
1230   if( pModule->xCreate!=0 && pModule->xCreate!=pModule->xConnect ) return 0;
1231   pTab = sqlite3DbMallocZero(db, sizeof(Table));
1232   if( pTab==0 ) return 0;
1233   pTab->zName = sqlite3DbStrDup(db, pMod->zName);
1234   if( pTab->zName==0 ){
1235     sqlite3DbFree(db, pTab);
1236     return 0;
1237   }
1238   pMod->pEpoTab = pTab;
1239   pTab->nTabRef = 1;
1240   pTab->eTabType = TABTYP_VTAB;
1241   pTab->pSchema = db->aDb[0].pSchema;
1242   assert( pTab->u.vtab.nArg==0 );
1243   pTab->iPKey = -1;
1244   pTab->tabFlags |= TF_Eponymous;
1245   addModuleArgument(pParse, pTab, sqlite3DbStrDup(db, pTab->zName));
1246   addModuleArgument(pParse, pTab, 0);
1247   addModuleArgument(pParse, pTab, sqlite3DbStrDup(db, pTab->zName));
1248   rc = vtabCallConstructor(db, pTab, pMod, pModule->xConnect, &zErr);
1249   if( rc ){
1250     sqlite3ErrorMsg(pParse, "%s", zErr);
1251     sqlite3DbFree(db, zErr);
1252     sqlite3VtabEponymousTableClear(db, pMod);
1253   }
1254   return 1;
1255 }
1256 
1257 /*
1258 ** Erase the eponymous virtual table instance associated with
1259 ** virtual table module pMod, if it exists.
1260 */
1261 void sqlite3VtabEponymousTableClear(sqlite3 *db, Module *pMod){
1262   Table *pTab = pMod->pEpoTab;
1263   if( pTab!=0 ){
1264     /* Mark the table as Ephemeral prior to deleting it, so that the
1265     ** sqlite3DeleteTable() routine will know that it is not stored in
1266     ** the schema. */
1267     pTab->tabFlags |= TF_Ephemeral;
1268     sqlite3DeleteTable(db, pTab);
1269     pMod->pEpoTab = 0;
1270   }
1271 }
1272 
1273 /*
1274 ** Return the ON CONFLICT resolution mode in effect for the virtual
1275 ** table update operation currently in progress.
1276 **
1277 ** The results of this routine are undefined unless it is called from
1278 ** within an xUpdate method.
1279 */
1280 int sqlite3_vtab_on_conflict(sqlite3 *db){
1281   static const unsigned char aMap[] = {
1282     SQLITE_ROLLBACK, SQLITE_ABORT, SQLITE_FAIL, SQLITE_IGNORE, SQLITE_REPLACE
1283   };
1284 #ifdef SQLITE_ENABLE_API_ARMOR
1285   if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
1286 #endif
1287   assert( OE_Rollback==1 && OE_Abort==2 && OE_Fail==3 );
1288   assert( OE_Ignore==4 && OE_Replace==5 );
1289   assert( db->vtabOnConflict>=1 && db->vtabOnConflict<=5 );
1290   return (int)aMap[db->vtabOnConflict-1];
1291 }
1292 
1293 /*
1294 ** Call from within the xCreate() or xConnect() methods to provide
1295 ** the SQLite core with additional information about the behavior
1296 ** of the virtual table being implemented.
1297 */
1298 int sqlite3_vtab_config(sqlite3 *db, int op, ...){
1299   va_list ap;
1300   int rc = SQLITE_OK;
1301   VtabCtx *p;
1302 
1303 #ifdef SQLITE_ENABLE_API_ARMOR
1304   if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
1305 #endif
1306   sqlite3_mutex_enter(db->mutex);
1307   p = db->pVtabCtx;
1308   if( !p ){
1309     rc = SQLITE_MISUSE_BKPT;
1310   }else{
1311     assert( p->pTab==0 || IsVirtual(p->pTab) );
1312     va_start(ap, op);
1313     switch( op ){
1314       case SQLITE_VTAB_CONSTRAINT_SUPPORT: {
1315         p->pVTable->bConstraint = (u8)va_arg(ap, int);
1316         break;
1317       }
1318       case SQLITE_VTAB_INNOCUOUS: {
1319         p->pVTable->eVtabRisk = SQLITE_VTABRISK_Low;
1320         break;
1321       }
1322       case SQLITE_VTAB_DIRECTONLY: {
1323         p->pVTable->eVtabRisk = SQLITE_VTABRISK_High;
1324         break;
1325       }
1326       default: {
1327         rc = SQLITE_MISUSE_BKPT;
1328         break;
1329       }
1330     }
1331     va_end(ap);
1332   }
1333 
1334   if( rc!=SQLITE_OK ) sqlite3Error(db, rc);
1335   sqlite3_mutex_leave(db->mutex);
1336   return rc;
1337 }
1338 
1339 #endif /* SQLITE_OMIT_VIRTUALTABLE */
1340