src/test8.c

   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 ** Code for testing the virtual table interfaces.  This code
  13 ** is not included in the SQLite library.  It is used for automated
  14 ** testing of the SQLite library.
  15 */
  16 #include "sqliteInt.h"
  17 #if defined(INCLUDE_SQLITE_TCL_H)
  18 #  include "sqlite_tcl.h"
  19 #else
  20 #  include "tcl.h"
  21 #endif
  22 #include <stdlib.h>
  23 #include <string.h>
  24
  25 #ifndef SQLITE_OMIT_VIRTUALTABLE
  26
  27 typedef struct echo_vtab echo_vtab;
  28 typedef struct echo_cursor echo_cursor;
  29
  30 /*
  31 ** The test module defined in this file uses four global Tcl variables to
  32 ** commicate with test-scripts:
  33 **
  34 **     $::echo_module
  35 **     $::echo_module_sync_fail
  36 **     $::echo_module_begin_fail
  37 **     $::echo_module_cost
  38 **
  39 ** The variable ::echo_module is a list. Each time one of the following
  40 ** methods is called, one or more elements are appended to the list.
  41 ** This is used for automated testing of virtual table modules.
  42 **
  43 ** The ::echo_module_sync_fail variable is set by test scripts and read
  44 ** by code in this file. If it is set to the name of a real table in the
  45 ** the database, then all xSync operations on echo virtual tables that
  46 ** use the named table as a backing store will fail.
  47 */
  48
  49 /*
  50 ** Errors can be provoked within the following echo virtual table methods:
  51 **
  52 **   xBestIndex   xOpen     xFilter   xNext
  53 **   xColumn      xRowid    xUpdate   xSync
  54 **   xBegin       xRename
  55 **
  56 ** This is done by setting the global tcl variable:
  57 **
  58 **   echo_module_fail($method,$tbl)
  59 **
  60 ** where $method is set to the name of the virtual table method to fail
  61 ** (i.e. "xBestIndex") and $tbl is the name of the table being echoed (not
  62 ** the name of the virtual table, the name of the underlying real table).
  63 */
  64
  65 /*
  66 ** An echo virtual-table object.
  67 **
  68 ** echo.vtab.aIndex is an array of booleans. The nth entry is true if
  69 ** the nth column of the real table is the left-most column of an index
  70 ** (implicit or otherwise). In other words, if SQLite can optimize
  71 ** a query like "SELECT * FROM real_table WHERE col = ?".
  72 **
  73 ** Member variable aCol[] contains copies of the column names of the real
  74 ** table.
  75 */
  76 struct echo_vtab {
  77   sqlite3_vtab base;
  78   Tcl_Interp *interp;     /* Tcl interpreter containing debug variables */
  79   sqlite3 *db;            /* Database connection */
  80
  81   int isPattern;
  82   int inTransaction;      /* True if within a transaction */
  83   char *zThis;            /* Name of the echo table */
  84   char *zTableName;       /* Name of the real table */
  85   char *zLogName;         /* Name of the log table */
  86   int nCol;               /* Number of columns in the real table */
  87   int *aIndex;            /* Array of size nCol. True if column has an index */
  88   char **aCol;            /* Array of size nCol. Column names */
  89 };
  90
  91 /* An echo cursor object */
  92 struct echo_cursor {
  93   sqlite3_vtab_cursor base;
  94   sqlite3_stmt *pStmt;
  95 };
  96
  97 static int simulateVtabError(echo_vtab *p, const char *zMethod){
  98   const char *zErr;
  99   char zVarname[128];
 100   zVarname[127] = '\0';
 101   sqlite3_snprintf(127, zVarname, "echo_module_fail(%s,%s)", zMethod, p->zTableName);
 102   zErr = Tcl_GetVar(p->interp, zVarname, TCL_GLOBAL_ONLY);
 103   if( zErr ){
 104     p->base.zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", zErr);
 105   }
 106   return (zErr!=0);
 107 }
 108
 109 /*
 110 ** Convert an SQL-style quoted string into a normal string by removing
 111 ** the quote characters.  The conversion is done in-place.  If the
 112 ** input does not begin with a quote character, then this routine
 113 ** is a no-op.
 114 **
 115 ** Examples:
 116 **
 117 **     "abc"   becomes   abc
 118 **     'xyz'   becomes   xyz
 119 **     [pqr]   becomes   pqr
 120 **     `mno`   becomes   mno
 121 */
 122 static void dequoteString(char *z){
 123   int quote;
 124   int i, j;
 125   if( z==0 ) return;
 126   quote = z[0];
 127   switch( quote ){
 128     case '\'':  break;
 129     case '"':   break;
 130     case '`':   break;                /* For MySQL compatibility */
 131     case '[':   quote = ']';  break;  /* For MS SqlServer compatibility */
 132     default:    return;
 133   }
 134   for(i=1, j=0; z[i]; i++){
 135     if( z[i]==quote ){
 136       if( z[i+1]==quote ){
 137         z[j++] = quote;
 138         i++;
 139       }else{
 140         z[j++] = 0;
 141         break;
 142       }
 143     }else{
 144       z[j++] = z[i];
 145     }
 146   }
 147 }
 148
 149 /*
 150 ** Retrieve the column names for the table named zTab via database
 151 ** connection db. SQLITE_OK is returned on success, or an sqlite error
 152 ** code otherwise.
 153 **
 154 ** If successful, the number of columns is written to *pnCol. *paCol is
 155 ** set to point at sqlite3_malloc()'d space containing the array of
 156 ** nCol column names. The caller is responsible for calling sqlite3_free
 157 ** on *paCol.
 158 */
 159 static int getColumnNames(
 160   sqlite3 *db,
 161   const char *zTab,
 162   char ***paCol,
 163   int *pnCol
 164 ){
 165   char **aCol = 0;
 166   char *zSql;
 167   sqlite3_stmt *pStmt = 0;
 168   int rc = SQLITE_OK;
 169   int nCol = 0;
 170
 171   /* Prepare the statement "SELECT * FROM <tbl>". The column names
 172   ** of the result set of the compiled SELECT will be the same as
 173   ** the column names of table <tbl>.
 174   */
 175   zSql = sqlite3_mprintf("SELECT * FROM %Q", zTab);
 176   if( !zSql ){
 177     rc = SQLITE_NOMEM;
 178     goto out;
 179   }
 180   rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
 181   sqlite3_free(zSql);
 182
 183   if( rc==SQLITE_OK ){
 184     int ii;
 185     int nBytes;
 186     char *zSpace;
 187     nCol = sqlite3_column_count(pStmt);
 188
 189     /* Figure out how much space to allocate for the array of column names
 190     ** (including space for the strings themselves). Then allocate it.
 191     */
 192     nBytes = sizeof(char *) * nCol;
 193     for(ii=0; ii<nCol; ii++){
 194       const char *zName = sqlite3_column_name(pStmt, ii);
 195       if( !zName ){
 196         rc = SQLITE_NOMEM;
 197         goto out;
 198       }
 199       nBytes += (int)strlen(zName)+1;
 200     }
 201     aCol = (char **)sqlite3MallocZero(nBytes);
 202     if( !aCol ){
 203       rc = SQLITE_NOMEM;
 204       goto out;
 205     }
 206
 207     /* Copy the column names into the allocated space and set up the
 208     ** pointers in the aCol[] array.
 209     */
 210     zSpace = (char *)(&aCol[nCol]);
 211     for(ii=0; ii<nCol; ii++){
 212       aCol[ii] = zSpace;
 213       sqlite3_snprintf(nBytes, zSpace, "%s", sqlite3_column_name(pStmt,ii));
 214       zSpace += (int)strlen(zSpace) + 1;
 215     }
 216     assert( (zSpace-nBytes)==(char *)aCol );
 217   }
 218
 219   *paCol = aCol;
 220   *pnCol = nCol;
 221
 222 out:
 223   sqlite3_finalize(pStmt);
 224   return rc;
 225 }
 226
 227 /*
 228 ** Parameter zTab is the name of a table in database db with nCol
 229 ** columns. This function allocates an array of integers nCol in
 230 ** size and populates it according to any implicit or explicit
 231 ** indices on table zTab.
 232 **
 233 ** If successful, SQLITE_OK is returned and *paIndex set to point
 234 ** at the allocated array. Otherwise, an error code is returned.
 235 **
 236 ** See comments associated with the member variable aIndex above
 237 ** "struct echo_vtab" for details of the contents of the array.
 238 */
 239 static int getIndexArray(
 240   sqlite3 *db,             /* Database connection */
 241   const char *zTab,        /* Name of table in database db */
 242   int nCol,
 243   int **paIndex
 244 ){
 245   sqlite3_stmt *pStmt = 0;
 246   int *aIndex = 0;
 247   int rc;
 248   char *zSql;
 249
 250   /* Allocate space for the index array */
 251   aIndex = (int *)sqlite3MallocZero(sizeof(int) * nCol);
 252   if( !aIndex ){
 253     rc = SQLITE_NOMEM;
 254     goto get_index_array_out;
 255   }
 256
 257   /* Compile an sqlite pragma to loop through all indices on table zTab */
 258   zSql = sqlite3_mprintf("PRAGMA index_list(%s)", zTab);
 259   if( !zSql ){
 260     rc = SQLITE_NOMEM;
 261     goto get_index_array_out;
 262   }
 263   rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
 264   sqlite3_free(zSql);
 265
 266   /* For each index, figure out the left-most column and set the
 267   ** corresponding entry in aIndex[] to 1.
 268   */
 269   while( pStmt && sqlite3_step(pStmt)==SQLITE_ROW ){
 270     const char *zIdx = (const char *)sqlite3_column_text(pStmt, 1);
 271     sqlite3_stmt *pStmt2 = 0;
 272     if( zIdx==0 ) continue;
 273     zSql = sqlite3_mprintf("PRAGMA index_info(%s)", zIdx);
 274     if( !zSql ){
 275       rc = SQLITE_NOMEM;
 276       goto get_index_array_out;
 277     }
 278     rc = sqlite3_prepare(db, zSql, -1, &pStmt2, 0);
 279     sqlite3_free(zSql);
 280     if( pStmt2 && sqlite3_step(pStmt2)==SQLITE_ROW ){
 281       int cid = sqlite3_column_int(pStmt2, 1);
 282       assert( cid>=0 && cid<nCol );
 283       aIndex[cid] = 1;
 284     }
 285     if( pStmt2 ){
 286       rc = sqlite3_finalize(pStmt2);
 287     }
 288     if( rc!=SQLITE_OK ){
 289       goto get_index_array_out;
 290     }
 291   }
 292
 293
 294 get_index_array_out:
 295   if( pStmt ){
 296     int rc2 = sqlite3_finalize(pStmt);
 297     if( rc==SQLITE_OK ){
 298       rc = rc2;
 299     }
 300   }
 301   if( rc!=SQLITE_OK ){
 302     sqlite3_free(aIndex);
 303     aIndex = 0;
 304   }
 305   *paIndex = aIndex;
 306   return rc;
 307 }
 308
 309 /*
 310 ** Global Tcl variable $echo_module is a list. This routine appends
 311 ** the string element zArg to that list in interpreter interp.
 312 */
 313 static void appendToEchoModule(Tcl_Interp *interp, const char *zArg){
 314   int flags = (TCL_APPEND_VALUE | TCL_LIST_ELEMENT | TCL_GLOBAL_ONLY);
 315   Tcl_SetVar(interp, "echo_module", (zArg?zArg:""), flags);
 316 }
 317
 318 /*
 319 ** This function is called from within the echo-modules xCreate and
 320 ** xConnect methods. The argc and argv arguments are copies of those
 321 ** passed to the calling method. This function is responsible for
 322 ** calling sqlite3_declare_vtab() to declare the schema of the virtual
 323 ** table being created or connected.
 324 **
 325 ** If the constructor was passed just one argument, i.e.:
 326 **
 327 **   CREATE TABLE t1 AS echo(t2);
 328 **
 329 ** Then t2 is assumed to be the name of a *real* database table. The
 330 ** schema of the virtual table is declared by passing a copy of the
 331 ** CREATE TABLE statement for the real table to sqlite3_declare_vtab().
 332 ** Hence, the virtual table should have exactly the same column names and
 333 ** types as the real table.
 334 */
 335 static int echoDeclareVtab(
 336   echo_vtab *pVtab,
 337   sqlite3 *db
 338 ){
 339   int rc = SQLITE_OK;
 340
 341   if( pVtab->zTableName ){
 342     sqlite3_stmt *pStmt = 0;
 343     rc = sqlite3_prepare(db,
 344         "SELECT sql FROM sqlite_master WHERE type = 'table' AND name = ?",
 345         -1, &pStmt, 0);
 346     if( rc==SQLITE_OK ){
 347       sqlite3_bind_text(pStmt, 1, pVtab->zTableName, -1, 0);
 348       if( sqlite3_step(pStmt)==SQLITE_ROW ){
 349         int rc2;
 350         const char *zCreateTable = (const char *)sqlite3_column_text(pStmt, 0);
 351         rc = sqlite3_declare_vtab(db, zCreateTable);
 352         rc2 = sqlite3_finalize(pStmt);
 353         if( rc==SQLITE_OK ){
 354           rc = rc2;
 355         }
 356       } else {
 357         rc = sqlite3_finalize(pStmt);
 358         if( rc==SQLITE_OK ){
 359           rc = SQLITE_ERROR;
 360         }
 361       }
 362       if( rc==SQLITE_OK ){
 363         rc = getColumnNames(db, pVtab->zTableName, &pVtab->aCol, &pVtab->nCol);
 364       }
 365       if( rc==SQLITE_OK ){
 366         rc = getIndexArray(db, pVtab->zTableName, pVtab->nCol, &pVtab->aIndex);
 367       }
 368     }
 369   }
 370
 371   return rc;
 372 }
 373
 374 /*
 375 ** This function frees all runtime structures associated with the virtual
 376 ** table pVtab.
 377 */
 378 static int echoDestructor(sqlite3_vtab *pVtab){
 379   echo_vtab *p = (echo_vtab*)pVtab;
 380   sqlite3_free(p->aIndex);
 381   sqlite3_free(p->aCol);
 382   sqlite3_free(p->zThis);
 383   sqlite3_free(p->zTableName);
 384   sqlite3_free(p->zLogName);
 385   sqlite3_free(p);
 386   return 0;
 387 }
 388
 389 typedef struct EchoModule EchoModule;
 390 struct EchoModule {
 391   Tcl_Interp *interp;
 392 };
 393
 394 /*
 395 ** This function is called to do the work of the xConnect() method -
 396 ** to allocate the required in-memory structures for a newly connected
 397 ** virtual table.
 398 */
 399 static int echoConstructor(
 400   sqlite3 *db,
 401   void *pAux,
 402   int argc, const char *const*argv,
 403   sqlite3_vtab **ppVtab,
 404   char **pzErr
 405 ){
 406   int rc;
 407   int i;
 408   echo_vtab *pVtab;
 409
 410   /* Allocate the sqlite3_vtab/echo_vtab structure itself */
 411   pVtab = sqlite3MallocZero( sizeof(*pVtab) );
 412   if( !pVtab ){
 413     return SQLITE_NOMEM;
 414   }
 415   pVtab->interp = ((EchoModule *)pAux)->interp;
 416   pVtab->db = db;
 417
 418   /* Allocate echo_vtab.zThis */
 419   pVtab->zThis = sqlite3_mprintf("%s", argv[2]);
 420   if( !pVtab->zThis ){
 421     echoDestructor((sqlite3_vtab *)pVtab);
 422     return SQLITE_NOMEM;
 423   }
 424
 425   /* Allocate echo_vtab.zTableName */
 426   if( argc>3 ){
 427     pVtab->zTableName = sqlite3_mprintf("%s", argv[3]);
 428     dequoteString(pVtab->zTableName);
 429     if( pVtab->zTableName && pVtab->zTableName[0]=='*' ){
 430       char *z = sqlite3_mprintf("%s%s", argv[2], &(pVtab->zTableName[1]));
 431       sqlite3_free(pVtab->zTableName);
 432       pVtab->zTableName = z;
 433       pVtab->isPattern = 1;
 434     }
 435     if( !pVtab->zTableName ){
 436       echoDestructor((sqlite3_vtab *)pVtab);
 437       return SQLITE_NOMEM;
 438     }
 439   }
 440
 441   /* Log the arguments to this function to Tcl var ::echo_module */
 442   for(i=0; i<argc; i++){
 443     appendToEchoModule(pVtab->interp, argv[i]);
 444   }
 445
 446   /* Invoke sqlite3_declare_vtab and set up other members of the echo_vtab
 447   ** structure. If an error occurs, delete the sqlite3_vtab structure and
 448   ** return an error code.
 449   */
 450   rc = echoDeclareVtab(pVtab, db);
 451   if( rc!=SQLITE_OK ){
 452     echoDestructor((sqlite3_vtab *)pVtab);
 453     return rc;
 454   }
 455
 456   /* Success. Set *ppVtab and return */
 457   *ppVtab = &pVtab->base;
 458   return SQLITE_OK;
 459 }
 460
 461 /*
 462 ** Echo virtual table module xCreate method.
 463 */
 464 static int echoCreate(
 465   sqlite3 *db,
 466   void *pAux,
 467   int argc, const char *const*argv,
 468   sqlite3_vtab **ppVtab,
 469   char **pzErr
 470 ){
 471   int rc = SQLITE_OK;
 472   appendToEchoModule(((EchoModule *)pAux)->interp, "xCreate");
 473   rc = echoConstructor(db, pAux, argc, argv, ppVtab, pzErr);
 474
 475   /* If there were two arguments passed to the module at the SQL level
 476   ** (i.e. "CREATE VIRTUAL TABLE tbl USING echo(arg1, arg2)"), then
 477   ** the second argument is used as a table name. Attempt to create
 478   ** such a table with a single column, "logmsg". This table will
 479   ** be used to log calls to the xUpdate method. It will be deleted
 480   ** when the virtual table is DROPed.
 481   **
 482   ** Note: The main point of this is to test that we can drop tables
 483   ** from within an xDestroy method call.
 484   */
 485   if( rc==SQLITE_OK && argc==5 ){
 486     char *zSql;
 487     echo_vtab *pVtab = *(echo_vtab **)ppVtab;
 488     pVtab->zLogName = sqlite3_mprintf("%s", argv[4]);
 489     zSql = sqlite3_mprintf("CREATE TABLE %Q(logmsg)", pVtab->zLogName);
 490     rc = sqlite3_exec(db, zSql, 0, 0, 0);
 491     sqlite3_free(zSql);
 492     if( rc!=SQLITE_OK ){
 493       *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
 494     }
 495   }
 496
 497   if( *ppVtab && rc!=SQLITE_OK ){
 498     echoDestructor(*ppVtab);
 499     *ppVtab = 0;
 500   }
 501
 502   if( rc==SQLITE_OK ){
 503     (*(echo_vtab**)ppVtab)->inTransaction = 1;
 504   }
 505
 506   return rc;
 507 }
 508
 509 /*
 510 ** Echo virtual table module xConnect method.
 511 */
 512 static int echoConnect(
 513   sqlite3 *db,
 514   void *pAux,
 515   int argc, const char *const*argv,
 516   sqlite3_vtab **ppVtab,
 517   char **pzErr
 518 ){
 519   appendToEchoModule(((EchoModule *)pAux)->interp, "xConnect");
 520   return echoConstructor(db, pAux, argc, argv, ppVtab, pzErr);
 521 }
 522
 523 /*
 524 ** Echo virtual table module xDisconnect method.
 525 */
 526 static int echoDisconnect(sqlite3_vtab *pVtab){
 527   appendToEchoModule(((echo_vtab *)pVtab)->interp, "xDisconnect");
 528   return echoDestructor(pVtab);
 529 }
 530
 531 /*
 532 ** Echo virtual table module xDestroy method.
 533 */
 534 static int echoDestroy(sqlite3_vtab *pVtab){
 535   int rc = SQLITE_OK;
 536   echo_vtab *p = (echo_vtab *)pVtab;
 537   appendToEchoModule(((echo_vtab *)pVtab)->interp, "xDestroy");
 538
 539   /* Drop the "log" table, if one exists (see echoCreate() for details) */
 540   if( p && p->zLogName ){
 541     char *zSql;
 542     zSql = sqlite3_mprintf("DROP TABLE %Q", p->zLogName);
 543     rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
 544     sqlite3_free(zSql);
 545   }
 546
 547   if( rc==SQLITE_OK ){
 548     rc = echoDestructor(pVtab);
 549   }
 550   return rc;
 551 }
 552
 553 /*
 554 ** Echo virtual table module xOpen method.
 555 */
 556 static int echoOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
 557   echo_cursor *pCur;
 558   if( simulateVtabError((echo_vtab *)pVTab, "xOpen") ){
 559     return SQLITE_ERROR;
 560   }
 561   pCur = sqlite3MallocZero(sizeof(echo_cursor));
 562   *ppCursor = (sqlite3_vtab_cursor *)pCur;
 563   return (pCur ? SQLITE_OK : SQLITE_NOMEM);
 564 }
 565
 566 /*
 567 ** Echo virtual table module xClose method.
 568 */
 569 static int echoClose(sqlite3_vtab_cursor *cur){
 570   int rc;
 571   echo_cursor *pCur = (echo_cursor *)cur;
 572   sqlite3_stmt *pStmt = pCur->pStmt;
 573   pCur->pStmt = 0;
 574   sqlite3_free(pCur);
 575   rc = sqlite3_finalize(pStmt);
 576   return rc;
 577 }
 578
 579 /*
 580 ** Return non-zero if the cursor does not currently point to a valid record
 581 ** (i.e if the scan has finished), or zero otherwise.
 582 */
 583 static int echoEof(sqlite3_vtab_cursor *cur){
 584   return (((echo_cursor *)cur)->pStmt ? 0 : 1);
 585 }
 586
 587 /*
 588 ** Echo virtual table module xNext method.
 589 */
 590 static int echoNext(sqlite3_vtab_cursor *cur){
 591   int rc = SQLITE_OK;
 592   echo_cursor *pCur = (echo_cursor *)cur;
 593
 594   if( simulateVtabError((echo_vtab *)(cur->pVtab), "xNext") ){
 595     return SQLITE_ERROR;
 596   }
 597
 598   if( pCur->pStmt ){
 599     rc = sqlite3_step(pCur->pStmt);
 600     if( rc==SQLITE_ROW ){
 601       rc = SQLITE_OK;
 602     }else{
 603       rc = sqlite3_finalize(pCur->pStmt);
 604       pCur->pStmt = 0;
 605     }
 606   }
 607
 608   return rc;
 609 }
 610
 611 /*
 612 ** Echo virtual table module xColumn method.
 613 */
 614 static int echoColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
 615   int iCol = i + 1;
 616   sqlite3_stmt *pStmt = ((echo_cursor *)cur)->pStmt;
 617
 618   if( simulateVtabError((echo_vtab *)(cur->pVtab), "xColumn") ){
 619     return SQLITE_ERROR;
 620   }
 621
 622   if( !pStmt ){
 623     sqlite3_result_null(ctx);
 624   }else{
 625     assert( sqlite3_data_count(pStmt)>iCol );
 626     sqlite3_result_value(ctx, sqlite3_column_value(pStmt, iCol));
 627   }
 628   return SQLITE_OK;
 629 }
 630
 631 /*
 632 ** Echo virtual table module xRowid method.
 633 */
 634 static int echoRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
 635   sqlite3_stmt *pStmt = ((echo_cursor *)cur)->pStmt;
 636
 637   if( simulateVtabError((echo_vtab *)(cur->pVtab), "xRowid") ){
 638     return SQLITE_ERROR;
 639   }
 640
 641   *pRowid = sqlite3_column_int64(pStmt, 0);
 642   return SQLITE_OK;
 643 }
 644
 645 /*
 646 ** Compute a simple hash of the null terminated string zString.
 647 **
 648 ** This module uses only sqlite3_index_info.idxStr, not
 649 ** sqlite3_index_info.idxNum. So to test idxNum, when idxStr is set
 650 ** in echoBestIndex(), idxNum is set to the corresponding hash value.
 651 ** In echoFilter(), code assert()s that the supplied idxNum value is
 652 ** indeed the hash of the supplied idxStr.
 653 */
 654 static int hashString(const char *zString){
 655   u32 val = 0;
 656   int ii;
 657   for(ii=0; zString[ii]; ii++){
 658     val = (val << 3) + (int)zString[ii];
 659   }
 660   return (int)(val&0x7fffffff);
 661 }
 662
 663 /*
 664 ** Echo virtual table module xFilter method.
 665 */
 666 static int echoFilter(
 667   sqlite3_vtab_cursor *pVtabCursor,
 668   int idxNum, const char *idxStr,
 669   int argc, sqlite3_value **argv
 670 ){
 671   int rc;
 672   int i;
 673
 674   echo_cursor *pCur = (echo_cursor *)pVtabCursor;
 675   echo_vtab *pVtab = (echo_vtab *)pVtabCursor->pVtab;
 676   sqlite3 *db = pVtab->db;
 677
 678   if( simulateVtabError(pVtab, "xFilter") ){
 679     return SQLITE_ERROR;
 680   }
 681
 682   /* Check that idxNum matches idxStr */
 683   assert( idxNum==hashString(idxStr) );
 684
 685   /* Log arguments to the ::echo_module Tcl variable */
 686   appendToEchoModule(pVtab->interp, "xFilter");
 687   appendToEchoModule(pVtab->interp, idxStr);
 688   for(i=0; i<argc; i++){
 689     appendToEchoModule(pVtab->interp, (const char*)sqlite3_value_text(argv[i]));
 690   }
 691
 692   sqlite3_finalize(pCur->pStmt);
 693   pCur->pStmt = 0;
 694
 695   /* Prepare the SQL statement created by echoBestIndex and bind the
 696   ** runtime parameters passed to this function to it.
 697   */
 698   rc = sqlite3_prepare(db, idxStr, -1, &pCur->pStmt, 0);
 699   assert( pCur->pStmt || rc!=SQLITE_OK );
 700   for(i=0; rc==SQLITE_OK && i<argc; i++){
 701     rc = sqlite3_bind_value(pCur->pStmt, i+1, argv[i]);
 702   }
 703
 704   /* If everything was successful, advance to the first row of the scan */
 705   if( rc==SQLITE_OK ){
 706     rc = echoNext(pVtabCursor);
 707   }
 708
 709   return rc;
 710 }
 711
 712
 713 /*
 714 ** A helper function used by echoUpdate() and echoBestIndex() for
 715 ** manipulating strings in concert with the sqlite3_mprintf() function.
 716 **
 717 ** Parameter pzStr points to a pointer to a string allocated with
 718 ** sqlite3_mprintf. The second parameter, zAppend, points to another
 719 ** string. The two strings are concatenated together and *pzStr
 720 ** set to point at the result. The initial buffer pointed to by *pzStr
 721 ** is deallocated via sqlite3_free().
 722 **
 723 ** If the third argument, doFree, is true, then sqlite3_free() is
 724 ** also called to free the buffer pointed to by zAppend.
 725 */
 726 static void string_concat(char **pzStr, char *zAppend, int doFree, int *pRc){
 727   char *zIn = *pzStr;
 728   if( !zAppend && doFree && *pRc==SQLITE_OK ){
 729     *pRc = SQLITE_NOMEM;
 730   }
 731   if( *pRc!=SQLITE_OK ){
 732     sqlite3_free(zIn);
 733     zIn = 0;
 734   }else{
 735     if( zIn ){
 736       char *zTemp = zIn;
 737       zIn = sqlite3_mprintf("%s%s", zIn, zAppend);
 738       sqlite3_free(zTemp);
 739     }else{
 740       zIn = sqlite3_mprintf("%s", zAppend);
 741     }
 742     if( !zIn ){
 743       *pRc = SQLITE_NOMEM;
 744     }
 745   }
 746   *pzStr = zIn;
 747   if( doFree ){
 748     sqlite3_free(zAppend);
 749   }
 750 }
 751
 752 /*
 753 ** This function returns a pointer to an sqlite3_malloc()ed buffer
 754 ** containing the select-list (the thing between keywords SELECT and FROM)
 755 ** to query the underlying real table with for the scan described by
 756 ** argument pIdxInfo.
 757 **
 758 ** If the current SQLite version is earlier than 3.10.0, this is just "*"
 759 ** (select all columns). Or, for version 3.10.0 and greater, the list of
 760 ** columns identified by the pIdxInfo->colUsed mask.
 761 */
 762 static char *echoSelectList(echo_vtab *pTab, sqlite3_index_info *pIdxInfo){
 763   char *zRet = 0;
 764   if( sqlite3_libversion_number()<3010000 ){
 765     zRet = sqlite3_mprintf(", *");
 766   }else{
 767     int i;
 768     for(i=0; i<pTab->nCol; i++){
 769       if( pIdxInfo->colUsed & ((sqlite3_uint64)1 << (i>=63 ? 63 : i)) ){
 770         zRet = sqlite3_mprintf("%z, %s", zRet, pTab->aCol[i]);
 771       }else{
 772         zRet = sqlite3_mprintf("%z, NULL", zRet);
 773       }
 774       if( !zRet ) break;
 775     }
 776   }
 777   return zRet;
 778 }
 779
 780 /*
 781 ** The echo module implements the subset of query constraints and sort
 782 ** orders that may take advantage of SQLite indices on the underlying
 783 ** real table. For example, if the real table is declared as:
 784 **
 785 **     CREATE TABLE real(a, b, c);
 786 **     CREATE INDEX real_index ON real(b);
 787 **
 788 ** then the echo module handles WHERE or ORDER BY clauses that refer
 789 ** to the column "b", but not "a" or "c". If a multi-column index is
 790 ** present, only its left most column is considered.
 791 **
 792 ** This xBestIndex method encodes the proposed search strategy as
 793 ** an SQL query on the real table underlying the virtual echo module
 794 ** table and stores the query in sqlite3_index_info.idxStr. The SQL
 795 ** statement is of the form:
 796 **
 797 **   SELECT rowid, * FROM <real-table> ?<where-clause>? ?<order-by-clause>?
 798 **
 799 ** where the <where-clause> and <order-by-clause> are determined
 800 ** by the contents of the structure pointed to by the pIdxInfo argument.
 801 */
 802 static int echoBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
 803   int ii;
 804   char *zQuery = 0;
 805   char *zCol = 0;
 806   char *zNew;
 807   int nArg = 0;
 808   const char *zSep = "WHERE";
 809   echo_vtab *pVtab = (echo_vtab *)tab;
 810   sqlite3_stmt *pStmt = 0;
 811   Tcl_Interp *interp = pVtab->interp;
 812
 813   int nRow = 0;
 814   int useIdx = 0;
 815   int rc = SQLITE_OK;
 816   int useCost = 0;
 817   double cost = 0;
 818   int isIgnoreUsable = 0;
 819   if( Tcl_GetVar(interp, "echo_module_ignore_usable", TCL_GLOBAL_ONLY) ){
 820     isIgnoreUsable = 1;
 821   }
 822
 823   if( simulateVtabError(pVtab, "xBestIndex") ){
 824     return SQLITE_ERROR;
 825   }
 826
 827   /* Determine the number of rows in the table and store this value in local
 828   ** variable nRow. The 'estimated-cost' of the scan will be the number of
 829   ** rows in the table for a linear scan, or the log (base 2) of the
 830   ** number of rows if the proposed scan uses an index.
 831   */
 832   if( Tcl_GetVar(interp, "echo_module_cost", TCL_GLOBAL_ONLY) ){
 833     cost = atof(Tcl_GetVar(interp, "echo_module_cost", TCL_GLOBAL_ONLY));
 834     useCost = 1;
 835   } else {
 836     zQuery = sqlite3_mprintf("SELECT count(*) FROM %Q", pVtab->zTableName);
 837     if( !zQuery ){
 838       return SQLITE_NOMEM;
 839     }
 840     rc = sqlite3_prepare(pVtab->db, zQuery, -1, &pStmt, 0);
 841     sqlite3_free(zQuery);
 842     if( rc!=SQLITE_OK ){
 843       return rc;
 844     }
 845     sqlite3_step(pStmt);
 846     nRow = sqlite3_column_int(pStmt, 0);
 847     rc = sqlite3_finalize(pStmt);
 848     if( rc!=SQLITE_OK ){
 849       return rc;
 850     }
 851   }
 852
 853   zCol = echoSelectList(pVtab, pIdxInfo);
 854   if( !zCol ) return SQLITE_NOMEM;
 855   zQuery = sqlite3_mprintf("SELECT rowid%z FROM %Q", zCol, pVtab->zTableName);
 856   if( !zQuery ) return SQLITE_NOMEM;
 857
 858   for(ii=0; ii<pIdxInfo->nConstraint; ii++){
 859     const struct sqlite3_index_constraint *pConstraint;
 860     struct sqlite3_index_constraint_usage *pUsage;
 861     int iCol;
 862
 863     pConstraint = &pIdxInfo->aConstraint[ii];
 864     pUsage = &pIdxInfo->aConstraintUsage[ii];
 865
 866     if( !isIgnoreUsable && !pConstraint->usable ) continue;
 867
 868     iCol = pConstraint->iColumn;
 869     if( iCol<0 || pVtab->aIndex[iCol] ){
 870       char *zNewCol = iCol>=0 ? pVtab->aCol[iCol] : "rowid";
 871       char *zOp = 0;
 872       useIdx = 1;
 873       switch( pConstraint->op ){
 874         case SQLITE_INDEX_CONSTRAINT_EQ:
 875           zOp = "="; break;
 876         case SQLITE_INDEX_CONSTRAINT_LT:
 877           zOp = "<"; break;
 878         case SQLITE_INDEX_CONSTRAINT_GT:
 879           zOp = ">"; break;
 880         case SQLITE_INDEX_CONSTRAINT_LE:
 881           zOp = "<="; break;
 882         case SQLITE_INDEX_CONSTRAINT_GE:
 883           zOp = ">="; break;
 884         case SQLITE_INDEX_CONSTRAINT_MATCH:
 885           /* Purposely translate the MATCH operator into a LIKE, which
 886           ** will be used by the next block of code to construct a new
 887           ** query.  It should also be noted here that the next block
 888           ** of code requires the first letter of this operator to be
 889           ** in upper-case to trigger the special MATCH handling (i.e.
 890           ** wrapping the bound parameter with literal '%'s).
 891           */
 892           zOp = "LIKE"; break;
 893         case SQLITE_INDEX_CONSTRAINT_LIKE:
 894           zOp = "like"; break;
 895         case SQLITE_INDEX_CONSTRAINT_GLOB:
 896           zOp = "glob"; break;
 897         case SQLITE_INDEX_CONSTRAINT_REGEXP:
 898           zOp = "regexp"; break;
 899       }
 900       if( zOp ){
 901         if( zOp[0]=='L' ){
 902           zNew = sqlite3_mprintf(" %s %s LIKE (SELECT '%%'||?||'%%')",
 903               zSep, zNewCol);
 904         } else {
 905           zNew = sqlite3_mprintf(" %s %s %s ?", zSep, zNewCol, zOp);
 906         }
 907         string_concat(&zQuery, zNew, 1, &rc);
 908         zSep = "AND";
 909         pUsage->argvIndex = ++nArg;
 910         pUsage->omit = 1;
 911       }
 912     }
 913   }
 914
 915   /* If there is only one term in the ORDER BY clause, and it is
 916   ** on a column that this virtual table has an index for, then consume
 917   ** the ORDER BY clause.
 918   */
 919   if( pIdxInfo->nOrderBy==1 && (
 920         pIdxInfo->aOrderBy->iColumn<0 ||
 921         pVtab->aIndex[pIdxInfo->aOrderBy->iColumn]) ){
 922     int iCol = pIdxInfo->aOrderBy->iColumn;
 923     char *zNewCol = iCol>=0 ? pVtab->aCol[iCol] : "rowid";
 924     char *zDir = pIdxInfo->aOrderBy->desc?"DESC":"ASC";
 925     zNew = sqlite3_mprintf(" ORDER BY %s %s", zNewCol, zDir);
 926     string_concat(&zQuery, zNew, 1, &rc);
 927     pIdxInfo->orderByConsumed = 1;
 928   }
 929
 930   appendToEchoModule(pVtab->interp, "xBestIndex");;
 931   appendToEchoModule(pVtab->interp, zQuery);
 932
 933   if( !zQuery ){
 934     return rc;
 935   }
 936   pIdxInfo->idxNum = hashString(zQuery);
 937   pIdxInfo->idxStr = zQuery;
 938   pIdxInfo->needToFreeIdxStr = 1;
 939   if( useCost ){
 940     pIdxInfo->estimatedCost = cost;
 941   }else if( useIdx ){
 942     /* Approximation of log2(nRow). */
 943     for( ii=0; ii<(sizeof(int)*8)-1; ii++ ){
 944       if( nRow & (1<<ii) ){
 945         pIdxInfo->estimatedCost = (double)ii;
 946       }
 947     }
 948   }else{
 949     pIdxInfo->estimatedCost = (double)nRow;
 950   }
 951   return rc;
 952 }
 953
 954 /*
 955 ** The xUpdate method for echo module virtual tables.
 956 **
 957 **    apData[0]  apData[1]  apData[2..]
 958 **
 959 **    INTEGER                              DELETE
 960 **
 961 **    INTEGER    NULL       (nCol args)    UPDATE (do not set rowid)
 962 **    INTEGER    INTEGER    (nCol args)    UPDATE (with SET rowid = <arg1>)
 963 **
 964 **    NULL       NULL       (nCol args)    INSERT INTO (automatic rowid value)
 965 **    NULL       INTEGER    (nCol args)    INSERT (incl. rowid value)
 966 **
 967 */
 968 int echoUpdate(
 969   sqlite3_vtab *tab,
 970   int nData,
 971   sqlite3_value **apData,
 972   sqlite_int64 *pRowid
 973 ){
 974   echo_vtab *pVtab = (echo_vtab *)tab;
 975   sqlite3 *db = pVtab->db;
 976   int rc = SQLITE_OK;
 977
 978   sqlite3_stmt *pStmt = 0;
 979   char *z = 0;               /* SQL statement to execute */
 980   int bindArgZero = 0;       /* True to bind apData[0] to sql var no. nData */
 981   int bindArgOne = 0;        /* True to bind apData[1] to sql var no. 1 */
 982   int i;                     /* Counter variable used by for loops */
 983
 984   assert( nData==pVtab->nCol+2 || nData==1 );
 985
 986   /* Ticket #3083 - make sure we always start a transaction prior to
 987   ** making any changes to a virtual table */
 988   assert( pVtab->inTransaction );
 989
 990   if( simulateVtabError(pVtab, "xUpdate") ){
 991     return SQLITE_ERROR;
 992   }
 993
 994   /* If apData[0] is an integer and nData>1 then do an UPDATE */
 995   if( nData>1 && sqlite3_value_type(apData[0])==SQLITE_INTEGER ){
 996     char *zSep = " SET";
 997     z = sqlite3_mprintf("UPDATE %Q", pVtab->zTableName);
 998     if( !z ){
 999       rc = SQLITE_NOMEM;
1000     }
1001
1002     bindArgOne = (apData[1] && sqlite3_value_type(apData[1])==SQLITE_INTEGER);
1003     bindArgZero = 1;
1004
1005     if( bindArgOne ){
1006        string_concat(&z, " SET rowid=?1 ", 0, &rc);
1007        zSep = ",";
1008     }
1009     for(i=2; i<nData; i++){
1010       if( apData[i]==0 ) continue;
1011       string_concat(&z, sqlite3_mprintf(
1012           "%s %Q=?%d", zSep, pVtab->aCol[i-2], i), 1, &rc);
1013       zSep = ",";
1014     }
1015     string_concat(&z, sqlite3_mprintf(" WHERE rowid=?%d", nData), 1, &rc);
1016   }
1017
1018   /* If apData[0] is an integer and nData==1 then do a DELETE */
1019   else if( nData==1 && sqlite3_value_type(apData[0])==SQLITE_INTEGER ){
1020     z = sqlite3_mprintf("DELETE FROM %Q WHERE rowid = ?1", pVtab->zTableName);
1021     if( !z ){
1022       rc = SQLITE_NOMEM;
1023     }
1024     bindArgZero = 1;
1025   }
1026
1027   /* If the first argument is NULL and there are more than two args, INSERT */
1028   else if( nData>2 && sqlite3_value_type(apData[0])==SQLITE_NULL ){
1029     int ii;
1030     char *zInsert = 0;
1031     char *zValues = 0;
1032
1033     zInsert = sqlite3_mprintf("INSERT INTO %Q (", pVtab->zTableName);
1034     if( !zInsert ){
1035       rc = SQLITE_NOMEM;
1036     }
1037     if( sqlite3_value_type(apData[1])==SQLITE_INTEGER ){
1038       bindArgOne = 1;
1039       zValues = sqlite3_mprintf("?");
1040       string_concat(&zInsert, "rowid", 0, &rc);
1041     }
1042
1043     assert((pVtab->nCol+2)==nData);
1044     for(ii=2; ii<nData; ii++){
1045       string_concat(&zInsert,
1046           sqlite3_mprintf("%s%Q", zValues?", ":"", pVtab->aCol[ii-2]), 1, &rc);
1047       string_concat(&zValues,
1048           sqlite3_mprintf("%s?%d", zValues?", ":"", ii), 1, &rc);
1049     }
1050
1051     string_concat(&z, zInsert, 1, &rc);
1052     string_concat(&z, ") VALUES(", 0, &rc);
1053     string_concat(&z, zValues, 1, &rc);
1054     string_concat(&z, ")", 0, &rc);
1055   }
1056
1057   /* Anything else is an error */
1058   else{
1059     assert(0);
1060     return SQLITE_ERROR;
1061   }
1062
1063   if( rc==SQLITE_OK ){
1064     rc = sqlite3_prepare(db, z, -1, &pStmt, 0);
1065   }
1066   assert( rc!=SQLITE_OK || pStmt );
1067   sqlite3_free(z);
1068   if( rc==SQLITE_OK ) {
1069     if( bindArgZero ){
1070       sqlite3_bind_value(pStmt, nData, apData[0]);
1071     }
1072     if( bindArgOne ){
1073       sqlite3_bind_value(pStmt, 1, apData[1]);
1074     }
1075     for(i=2; i<nData && rc==SQLITE_OK; i++){
1076       if( apData[i] ) rc = sqlite3_bind_value(pStmt, i, apData[i]);
1077     }
1078     if( rc==SQLITE_OK ){
1079       sqlite3_step(pStmt);
1080       rc = sqlite3_finalize(pStmt);
1081     }else{
1082       sqlite3_finalize(pStmt);
1083     }
1084   }
1085
1086   if( pRowid && rc==SQLITE_OK ){
1087     *pRowid = sqlite3_last_insert_rowid(db);
1088   }
1089   if( rc!=SQLITE_OK ){
1090     tab->zErrMsg = sqlite3_mprintf("echo-vtab-error: %s", sqlite3_errmsg(db));
1091   }
1092
1093   return rc;
1094 }
1095
1096 /*
1097 ** xBegin, xSync, xCommit and xRollback callbacks for echo module
1098 ** virtual tables. Do nothing other than add the name of the callback
1099 ** to the $::echo_module Tcl variable.
1100 */
1101 static int echoTransactionCall(sqlite3_vtab *tab, const char *zCall){
1102   char *z;
1103   echo_vtab *pVtab = (echo_vtab *)tab;
1104   z = sqlite3_mprintf("echo(%s)", pVtab->zTableName);
1105   if( z==0 ) return SQLITE_NOMEM;
1106   appendToEchoModule(pVtab->interp, zCall);
1107   appendToEchoModule(pVtab->interp, z);
1108   sqlite3_free(z);
1109   return SQLITE_OK;
1110 }
1111 static int echoBegin(sqlite3_vtab *tab){
1112   int rc;
1113   echo_vtab *pVtab = (echo_vtab *)tab;
1114   Tcl_Interp *interp = pVtab->interp;
1115   const char *zVal;
1116
1117   /* Ticket #3083 - do not start a transaction if we are already in
1118   ** a transaction */
1119   assert( !pVtab->inTransaction );
1120
1121   if( simulateVtabError(pVtab, "xBegin") ){
1122     return SQLITE_ERROR;
1123   }
1124
1125   rc = echoTransactionCall(tab, "xBegin");
1126
1127   if( rc==SQLITE_OK ){
1128     /* Check if the $::echo_module_begin_fail variable is defined. If it is,
1129     ** and it is set to the name of the real table underlying this virtual
1130     ** echo module table, then cause this xSync operation to fail.
1131     */
1132     zVal = Tcl_GetVar(interp, "echo_module_begin_fail", TCL_GLOBAL_ONLY);
1133     if( zVal && 0==strcmp(zVal, pVtab->zTableName) ){
1134       rc = SQLITE_ERROR;
1135     }
1136   }
1137   if( rc==SQLITE_OK ){
1138     pVtab->inTransaction = 1;
1139   }
1140   return rc;
1141 }
1142 static int echoSync(sqlite3_vtab *tab){
1143   int rc;
1144   echo_vtab *pVtab = (echo_vtab *)tab;
1145   Tcl_Interp *interp = pVtab->interp;
1146   const char *zVal;
1147
1148   /* Ticket #3083 - Only call xSync if we have previously started a
1149   ** transaction */
1150   assert( pVtab->inTransaction );
1151
1152   if( simulateVtabError(pVtab, "xSync") ){
1153     return SQLITE_ERROR;
1154   }
1155
1156   rc = echoTransactionCall(tab, "xSync");
1157
1158   if( rc==SQLITE_OK ){
1159     /* Check if the $::echo_module_sync_fail variable is defined. If it is,
1160     ** and it is set to the name of the real table underlying this virtual
1161     ** echo module table, then cause this xSync operation to fail.
1162     */
1163     zVal = Tcl_GetVar(interp, "echo_module_sync_fail", TCL_GLOBAL_ONLY);
1164     if( zVal && 0==strcmp(zVal, pVtab->zTableName) ){
1165       rc = -1;
1166     }
1167   }
1168   return rc;
1169 }
1170 static int echoCommit(sqlite3_vtab *tab){
1171   echo_vtab *pVtab = (echo_vtab*)tab;
1172   int rc;
1173
1174   /* Ticket #3083 - Only call xCommit if we have previously started
1175   ** a transaction */
1176   assert( pVtab->inTransaction );
1177
1178   if( simulateVtabError(pVtab, "xCommit") ){
1179     return SQLITE_ERROR;
1180   }
1181
1182   sqlite3BeginBenignMalloc();
1183   rc = echoTransactionCall(tab, "xCommit");
1184   sqlite3EndBenignMalloc();
1185   pVtab->inTransaction = 0;
1186   return rc;
1187 }
1188 static int echoRollback(sqlite3_vtab *tab){
1189   int rc;
1190   echo_vtab *pVtab = (echo_vtab*)tab;
1191
1192   /* Ticket #3083 - Only call xRollback if we have previously started
1193   ** a transaction */
1194   assert( pVtab->inTransaction );
1195
1196   rc = echoTransactionCall(tab, "xRollback");
1197   pVtab->inTransaction = 0;
1198   return rc;
1199 }
1200
1201 /*
1202 ** Implementation of "GLOB" function on the echo module.  Pass
1203 ** all arguments to the ::echo_glob_overload procedure of TCL
1204 ** and return the result of that procedure as a string.
1205 */
1206 static void overloadedGlobFunction(
1207   sqlite3_context *pContext,
1208   int nArg,
1209   sqlite3_value **apArg
1210 ){
1211   Tcl_Interp *interp = sqlite3_user_data(pContext);
1212   Tcl_DString str;
1213   int i;
1214   int rc;
1215   Tcl_DStringInit(&str);
1216   Tcl_DStringAppendElement(&str, "::echo_glob_overload");
1217   for(i=0; i<nArg; i++){
1218     Tcl_DStringAppendElement(&str, (char*)sqlite3_value_text(apArg[i]));
1219   }
1220   rc = Tcl_Eval(interp, Tcl_DStringValue(&str));
1221   Tcl_DStringFree(&str);
1222   if( rc ){
1223     sqlite3_result_error(pContext, Tcl_GetStringResult(interp), -1);
1224   }else{
1225     sqlite3_result_text(pContext, Tcl_GetStringResult(interp),
1226                         -1, SQLITE_TRANSIENT);
1227   }
1228   Tcl_ResetResult(interp);
1229 }
1230
1231 /*
1232 ** This is the xFindFunction implementation for the echo module.
1233 ** SQLite calls this routine when the first argument of a function
1234 ** is a column of an echo virtual table.  This routine can optionally
1235 ** override the implementation of that function.  It will choose to
1236 ** do so if the function is named "glob", and a TCL command named
1237 ** ::echo_glob_overload exists.
1238 */
1239 static int echoFindFunction(
1240   sqlite3_vtab *vtab,
1241   int nArg,
1242   const char *zFuncName,
1243   void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
1244   void **ppArg
1245 ){
1246   echo_vtab *pVtab = (echo_vtab *)vtab;
1247   Tcl_Interp *interp = pVtab->interp;
1248   Tcl_CmdInfo info;
1249   if( strcmp(zFuncName,"glob")!=0 ){
1250     return 0;
1251   }
1252   if( Tcl_GetCommandInfo(interp, "::echo_glob_overload", &info)==0 ){
1253     return 0;
1254   }
1255   *pxFunc = overloadedGlobFunction;
1256   *ppArg = interp;
1257   return 1;
1258 }
1259
1260 static int echoRename(sqlite3_vtab *vtab, const char *zNewName){
1261   int rc = SQLITE_OK;
1262   echo_vtab *p = (echo_vtab *)vtab;
1263
1264   if( simulateVtabError(p, "xRename") ){
1265     return SQLITE_ERROR;
1266   }
1267
1268   if( p->isPattern ){
1269     int nThis = (int)strlen(p->zThis);
1270     char *zSql = sqlite3_mprintf("ALTER TABLE %s RENAME TO %s%s",
1271         p->zTableName, zNewName, &p->zTableName[nThis]
1272     );
1273     rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
1274     sqlite3_free(zSql);
1275   }
1276
1277   return rc;
1278 }
1279
1280 static int echoSavepoint(sqlite3_vtab *pVTab, int iSavepoint){
1281   assert( pVTab );
1282   return SQLITE_OK;
1283 }
1284
1285 static int echoRelease(sqlite3_vtab *pVTab, int iSavepoint){
1286   assert( pVTab );
1287   return SQLITE_OK;
1288 }
1289
1290 static int echoRollbackTo(sqlite3_vtab *pVTab, int iSavepoint){
1291   assert( pVTab );
1292   return SQLITE_OK;
1293 }
1294
1295 /*
1296 ** A virtual table module that merely "echos" the contents of another
1297 ** table (like an SQL VIEW).
1298 */
1299 static sqlite3_module echoModule = {
1300   1,                         /* iVersion */
1301   echoCreate,
1302   echoConnect,
1303   echoBestIndex,
1304   echoDisconnect,
1305   echoDestroy,
1306   echoOpen,                  /* xOpen - open a cursor */
1307   echoClose,                 /* xClose - close a cursor */
1308   echoFilter,                /* xFilter - configure scan constraints */
1309   echoNext,                  /* xNext - advance a cursor */
1310   echoEof,                   /* xEof */
1311   echoColumn,                /* xColumn - read data */
1312   echoRowid,                 /* xRowid - read data */
1313   echoUpdate,                /* xUpdate - write data */
1314   echoBegin,                 /* xBegin - begin transaction */
1315   echoSync,                  /* xSync - sync transaction */
1316   echoCommit,                /* xCommit - commit transaction */
1317   echoRollback,              /* xRollback - rollback transaction */
1318   echoFindFunction,          /* xFindFunction - function overloading */
1319   echoRename                 /* xRename - rename the table */
1320 };
1321
1322 static sqlite3_module echoModuleV2 = {
1323   2,                         /* iVersion */
1324   echoCreate,
1325   echoConnect,
1326   echoBestIndex,
1327   echoDisconnect,
1328   echoDestroy,
1329   echoOpen,                  /* xOpen - open a cursor */
1330   echoClose,                 /* xClose - close a cursor */
1331   echoFilter,                /* xFilter - configure scan constraints */
1332   echoNext,                  /* xNext - advance a cursor */
1333   echoEof,                   /* xEof */
1334   echoColumn,                /* xColumn - read data */
1335   echoRowid,                 /* xRowid - read data */
1336   echoUpdate,                /* xUpdate - write data */
1337   echoBegin,                 /* xBegin - begin transaction */
1338   echoSync,                  /* xSync - sync transaction */
1339   echoCommit,                /* xCommit - commit transaction */
1340   echoRollback,              /* xRollback - rollback transaction */
1341   echoFindFunction,          /* xFindFunction - function overloading */
1342   echoRename,                /* xRename - rename the table */
1343   echoSavepoint,
1344   echoRelease,
1345   echoRollbackTo
1346 };
1347
1348 /*
1349 ** Decode a pointer to an sqlite3 object.
1350 */
1351 extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
1352 extern const char *sqlite3ErrName(int);
1353
1354 static void moduleDestroy(void *p){
1355   sqlite3_free(p);
1356 }
1357
1358 /*
1359 ** Register the echo virtual table module.
1360 */
1361 static int SQLITE_TCLAPI register_echo_module(
1362   ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
1363   Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
1364   int objc,              /* Number of arguments */
1365   Tcl_Obj *CONST objv[]  /* Command arguments */
1366 ){
1367   int rc;
1368   sqlite3 *db;
1369   EchoModule *pMod;
1370   if( objc!=2 ){
1371     Tcl_WrongNumArgs(interp, 1, objv, "DB");
1372     return TCL_ERROR;
1373   }
1374   if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
1375
1376   /* Virtual table module "echo" */
1377   pMod = sqlite3_malloc(sizeof(EchoModule));
1378   pMod->interp = interp;
1379   rc = sqlite3_create_module_v2(
1380       db, "echo", &echoModule, (void*)pMod, moduleDestroy
1381   );
1382
1383   /* Virtual table module "echo_v2" */
1384   if( rc==SQLITE_OK ){
1385     pMod = sqlite3_malloc(sizeof(EchoModule));
1386     pMod->interp = interp;
1387     rc = sqlite3_create_module_v2(db, "echo_v2",
1388         &echoModuleV2, (void*)pMod, moduleDestroy
1389     );
1390   }
1391
1392   Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
1393   return TCL_OK;
1394 }
1395
1396 /*
1397 ** Tcl interface to sqlite3_declare_vtab, invoked as follows from Tcl:
1398 **
1399 ** sqlite3_declare_vtab DB SQL
1400 */
1401 static int SQLITE_TCLAPI declare_vtab(
1402   ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
1403   Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
1404   int objc,              /* Number of arguments */
1405   Tcl_Obj *CONST objv[]  /* Command arguments */
1406 ){
1407   sqlite3 *db;
1408   int rc;
1409   if( objc!=3 ){
1410     Tcl_WrongNumArgs(interp, 1, objv, "DB SQL");
1411     return TCL_ERROR;
1412   }
1413   if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
1414   rc = sqlite3_declare_vtab(db, Tcl_GetString(objv[2]));
1415   if( rc!=SQLITE_OK ){
1416     Tcl_SetResult(interp, (char *)sqlite3_errmsg(db), TCL_VOLATILE);
1417     return TCL_ERROR;
1418   }
1419   return TCL_OK;
1420 }
1421
1422 #endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
1423
1424 /*
1425 ** Register commands with the TCL interpreter.
1426 */
1427 int Sqlitetest8_Init(Tcl_Interp *interp){
1428 #ifndef SQLITE_OMIT_VIRTUALTABLE
1429   static struct {
1430      char *zName;
1431      Tcl_ObjCmdProc *xProc;
1432      void *clientData;
1433   } aObjCmd[] = {
1434      { "register_echo_module",       register_echo_module, 0 },
1435      { "sqlite3_declare_vtab",       declare_vtab, 0 },
1436   };
1437   int i;
1438   for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
1439     Tcl_CreateObjCommand(interp, aObjCmd[i].zName,
1440         aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
1441   }
1442 #endif
1443   return TCL_OK;
1444 }