ext/misc/qpvtab.c

   1 /*
   2 ** 2022-01-19
   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 **
  13 ** This file implements a virtual-table that returns information about
  14 ** how the query planner called the xBestIndex method.  This virtual table
  15 ** is intended for testing and debugging only.
  16 **
  17 ** The schema of the virtual table is this:
  18 **
  19 **    CREATE TABLE qpvtab(
  20 **      vn     TEXT,           -- Name of an sqlite3_index_info field
  21 **      ix     INTEGER,        -- Array index or value
  22 **      cn     TEXT,           -- Column name
  23 **      op     INTEGER,        -- operator
  24 **      ux     BOOLEAN,        -- "usable" field
  25 **      rhs    TEXT,           -- sqlite3_vtab_rhs_value()
  26 **
  27 **      a, b, c, d, e,         -- Extra columns to attach constraints to
  28 **
  29 **      flags    INTEGER HIDDEN  -- control flags
  30 **    );
  31 **
  32 ** The virtual table returns a description of the sqlite3_index_info object
  33 ** that was provided to the (successful) xBestIndex method.  There is one
  34 ** row in the result table for each field in the sqlite3_index_info object.
  35 **
  36 ** The values of the "a" through "e" columns are one of:
  37 **
  38 **    1.   TEXT - the same as the column name
  39 **    2.   INTEGER - 1 for "a", 2 for "b", and so forth
  40 **
  41 ** Option 1 is the default behavior.  2 is use if there is a usable
  42 ** constraint on "flags" with an integer right-hand side that where the
  43 ** value of the right-hand side has its 0x001 bit set.
  44 **
  45 ** All constraints on columns "a" through "e" are marked as "omit".
  46 **
  47 ** If there is a usable constraint on "flags" that has a RHS value that
  48 ** is an integer and that integer has its 0x02 bit set, then the
  49 ** orderByConsumed flag is set.
  50 **
  51 ** FLAGS SUMMARY:
  52 **
  53 **   0x001               Columns 'a' through 'e' have INT values
  54 **   0x002               orderByConsumed is set
  55 **   0x004               OFFSET and LIMIT have omit set
  56 **
  57 ** COMPILE:
  58 **
  59 **   gcc -Wall -g -shared -fPIC -I. qpvtab.c -o qqvtab.so
  60 **
  61 ** EXAMPLE USAGE:
  62 **
  63 **   .load ./qpvtab
  64 **   SELECT rowid, *, flags FROM qpvtab(102)
  65 **    WHERE a=19
  66 **      AND b BETWEEN 4.5 and 'hello'
  67 **      AND c<>x'aabbcc'
  68 **    ORDER BY d, e DESC;
  69 */
  70 #if !defined(SQLITEINT_H)
  71 #include "sqlite3ext.h"
  72 #endif
  73 SQLITE_EXTENSION_INIT1
  74 #include <string.h>
  75 #include <assert.h>
  76 #include <stdlib.h>
  77
  78 #if !defined(SQLITE_OMIT_VIRTUALTABLE)
  79
  80 /* qpvtab_vtab is a subclass of sqlite3_vtab which is
  81 ** underlying representation of the virtual table
  82 */
  83 typedef struct qpvtab_vtab qpvtab_vtab;
  84 struct qpvtab_vtab {
  85   sqlite3_vtab base;  /* Base class - must be first */
  86 };
  87
  88 /* qpvtab_cursor is a subclass of sqlite3_vtab_cursor which will
  89 ** serve as the underlying representation of a cursor that scans
  90 ** over rows of the result
  91 */
  92 typedef struct qpvtab_cursor qpvtab_cursor;
  93 struct qpvtab_cursor {
  94   sqlite3_vtab_cursor base;  /* Base class - must be first */
  95   sqlite3_int64 iRowid;      /* The rowid */
  96   const char *zData;         /* Data to return */
  97   int nData;                 /* Number of bytes of data */
  98   int flags;                 /* Flags value */
  99 };
 100
 101 /*
 102 ** Names of columns
 103 */
 104 static const char *azColname[] = {
 105   "vn",
 106   "ix",
 107   "cn",
 108   "op",
 109   "ux",
 110   "rhs",
 111   "a", "b", "c", "d", "e",
 112   "flags",
 113   ""
 114 };
 115
 116 /*
 117 ** The qpvtabConnect() method is invoked to create a new
 118 ** qpvtab virtual table.
 119 */
 120 static int qpvtabConnect(
 121   sqlite3 *db,
 122   void *pAux,
 123   int argc, const char *const*argv,
 124   sqlite3_vtab **ppVtab,
 125   char **pzErr
 126 ){
 127   qpvtab_vtab *pNew;
 128   int rc;
 129
 130   rc = sqlite3_declare_vtab(db,
 131          "CREATE TABLE x("
 132          " vn TEXT,"
 133          " ix INT,"
 134          " cn TEXT,"
 135          " op INT,"
 136          " ux BOOLEAN,"
 137          " rhs TEXT,"
 138          " a, b, c, d, e,"
 139          " flags INT HIDDEN)"
 140        );
 141 #define QPVTAB_VN      0
 142 #define QPVTAB_IX      1
 143 #define QPVTAB_CN      2
 144 #define QPVTAB_OP      3
 145 #define QPVTAB_UX      4
 146 #define QPVTAB_RHS     5
 147 #define QPVTAB_A       6
 148 #define QPVTAB_B       7
 149 #define QPVTAB_C       8
 150 #define QPVTAB_D       9
 151 #define QPVTAB_E      10
 152 #define QPVTAB_FLAGS  11
 153 #define QPVTAB_NONE   12
 154   if( rc==SQLITE_OK ){
 155     pNew = sqlite3_malloc( sizeof(*pNew) );
 156     *ppVtab = (sqlite3_vtab*)pNew;
 157     if( pNew==0 ) return SQLITE_NOMEM;
 158     memset(pNew, 0, sizeof(*pNew));
 159   }
 160   return rc;
 161 }
 162
 163 /*
 164 ** This method is the destructor for qpvtab_vtab objects.
 165 */
 166 static int qpvtabDisconnect(sqlite3_vtab *pVtab){
 167   qpvtab_vtab *p = (qpvtab_vtab*)pVtab;
 168   sqlite3_free(p);
 169   return SQLITE_OK;
 170 }
 171
 172 /*
 173 ** Constructor for a new qpvtab_cursor object.
 174 */
 175 static int qpvtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
 176   qpvtab_cursor *pCur;
 177   pCur = sqlite3_malloc( sizeof(*pCur) );
 178   if( pCur==0 ) return SQLITE_NOMEM;
 179   memset(pCur, 0, sizeof(*pCur));
 180   *ppCursor = &pCur->base;
 181   return SQLITE_OK;
 182 }
 183
 184 /*
 185 ** Destructor for a qpvtab_cursor.
 186 */
 187 static int qpvtabClose(sqlite3_vtab_cursor *cur){
 188   qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
 189   sqlite3_free(pCur);
 190   return SQLITE_OK;
 191 }
 192
 193
 194 /*
 195 ** Advance a qpvtab_cursor to its next row of output.
 196 */
 197 static int qpvtabNext(sqlite3_vtab_cursor *cur){
 198   qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
 199   if( pCur->iRowid<pCur->nData ){
 200     const char *z = &pCur->zData[pCur->iRowid];
 201     const char *zEnd = strchr(z, '\n');
 202     if( zEnd ) zEnd++;
 203     pCur->iRowid = (int)(zEnd - pCur->zData);
 204   }
 205   return SQLITE_OK;
 206 }
 207
 208 /*
 209 ** Return values of columns for the row at which the qpvtab_cursor
 210 ** is currently pointing.
 211 */
 212 static int qpvtabColumn(
 213   sqlite3_vtab_cursor *cur,   /* The cursor */
 214   sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
 215   int i                       /* Which column to return */
 216 ){
 217   qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
 218   if( i>=QPVTAB_VN && i<=QPVTAB_RHS && pCur->iRowid<pCur->nData ){
 219     const char *z = &pCur->zData[pCur->iRowid];
 220     const char *zEnd;
 221     int j;
 222     j = QPVTAB_VN;
 223     while(1){
 224       zEnd = strchr(z, j==QPVTAB_RHS ? '\n' : ',');
 225       if( j==i || zEnd==0 ) break;
 226       z = zEnd+1;
 227       j++;
 228     }
 229     if( zEnd==z ){
 230       sqlite3_result_null(ctx);
 231     }else if( i==QPVTAB_IX || i==QPVTAB_OP || i==QPVTAB_UX ){
 232       sqlite3_result_int(ctx, atoi(z));
 233     }else{
 234       sqlite3_result_text64(ctx, z, zEnd-z, SQLITE_TRANSIENT, SQLITE_UTF8);
 235     }
 236   }else if( i>=QPVTAB_A && i<=QPVTAB_E ){
 237     if( pCur->flags & 0x001 ){
 238       sqlite3_result_int(ctx, i-QPVTAB_A+1);
 239     }else{
 240       char x = 'a'+i-QPVTAB_A;
 241       sqlite3_result_text64(ctx, &x, 1, SQLITE_TRANSIENT, SQLITE_UTF8);
 242     }
 243   }else if( i==QPVTAB_FLAGS ){
 244     sqlite3_result_int(ctx, pCur->flags);
 245   }
 246   return SQLITE_OK;
 247 }
 248
 249 /*
 250 ** Return the rowid for the current row.  In this implementation, the
 251 ** rowid is the same as the output value.
 252 */
 253 static int qpvtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
 254   qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
 255   *pRowid = pCur->iRowid;
 256   return SQLITE_OK;
 257 }
 258
 259 /*
 260 ** Return TRUE if the cursor has been moved off of the last
 261 ** row of output.
 262 */
 263 static int qpvtabEof(sqlite3_vtab_cursor *cur){
 264   qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
 265   return pCur->iRowid>=pCur->nData;
 266 }
 267
 268 /*
 269 ** This method is called to "rewind" the qpvtab_cursor object back
 270 ** to the first row of output.  This method is always called at least
 271 ** once prior to any call to qpvtabColumn() or qpvtabRowid() or
 272 ** qpvtabEof().
 273 */
 274 static int qpvtabFilter(
 275   sqlite3_vtab_cursor *pVtabCursor,
 276   int idxNum, const char *idxStr,
 277   int argc, sqlite3_value **argv
 278 ){
 279   qpvtab_cursor *pCur = (qpvtab_cursor *)pVtabCursor;
 280   pCur->iRowid = 0;
 281   pCur->zData = idxStr;
 282   pCur->nData = (int)strlen(idxStr);
 283   pCur->flags = idxNum;
 284   return SQLITE_OK;
 285 }
 286
 287 /*
 288 ** Append the text of a value to pStr
 289 */
 290 static void qpvtabStrAppendValue(
 291   sqlite3_str *pStr,
 292   sqlite3_value *pVal
 293 ){
 294   switch( sqlite3_value_type(pVal) ){
 295     case SQLITE_NULL:
 296       sqlite3_str_appendf(pStr, "NULL");
 297       break;
 298     case SQLITE_INTEGER:
 299       sqlite3_str_appendf(pStr, "%lld", sqlite3_value_int64(pVal));
 300       break;
 301     case SQLITE_FLOAT:
 302       sqlite3_str_appendf(pStr, "%!f", sqlite3_value_double(pVal));
 303       break;
 304     case SQLITE_TEXT: {
 305       int i;
 306       const char *a = (const char*)sqlite3_value_text(pVal);
 307       int n = sqlite3_value_bytes(pVal);
 308       sqlite3_str_append(pStr, "'", 1);
 309       for(i=0; i<n; i++){
 310         char c = a[i];
 311         if( c=='\n' ) c = ' ';
 312         sqlite3_str_append(pStr, &c, 1);
 313         if( c=='\'' ) sqlite3_str_append(pStr, &c, 1);
 314       }
 315       sqlite3_str_append(pStr, "'", 1);
 316       break;
 317     }
 318     case SQLITE_BLOB: {
 319       int i;
 320       const unsigned char *a = sqlite3_value_blob(pVal);
 321       int n = sqlite3_value_bytes(pVal);
 322       sqlite3_str_append(pStr, "x'", 2);
 323       for(i=0; i<n; i++){
 324         sqlite3_str_appendf(pStr, "%02x", a[i]);
 325       }
 326       sqlite3_str_append(pStr, "'", 1);
 327       break;
 328     }
 329   }
 330 }
 331
 332 /*
 333 ** SQLite will invoke this method one or more times while planning a query
 334 ** that uses the virtual table.  This routine needs to create
 335 ** a query plan for each invocation and compute an estimated cost for that
 336 ** plan.
 337 */
 338 static int qpvtabBestIndex(
 339   sqlite3_vtab *tab,
 340   sqlite3_index_info *pIdxInfo
 341 ){
 342   sqlite3_str *pStr = sqlite3_str_new(0);
 343   int i, k = 0;
 344   int rc;
 345   sqlite3_str_appendf(pStr, "nConstraint,%d,,,,\n", pIdxInfo->nConstraint);
 346   for(i=0; i<pIdxInfo->nConstraint; i++){
 347     sqlite3_value *pVal;
 348     int iCol = pIdxInfo->aConstraint[i].iColumn;
 349     int op = pIdxInfo->aConstraint[i].op;
 350     if( iCol==QPVTAB_FLAGS &&  pIdxInfo->aConstraint[i].usable ){
 351       pVal = 0;
 352       rc = sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
 353       assert( rc==SQLITE_OK || pVal==0 );
 354       if( pVal ){
 355         pIdxInfo->idxNum = sqlite3_value_int(pVal);
 356         if( pIdxInfo->idxNum & 0x002 ) pIdxInfo->orderByConsumed = 1;
 357       }
 358     }
 359     if( op==SQLITE_INDEX_CONSTRAINT_LIMIT
 360      || op==SQLITE_INDEX_CONSTRAINT_OFFSET
 361     ){
 362       iCol = QPVTAB_NONE;
 363     }
 364     sqlite3_str_appendf(pStr,"aConstraint,%d,%s,%d,%d,",
 365        i,
 366        azColname[iCol],
 367        op,
 368        pIdxInfo->aConstraint[i].usable);
 369     pVal = 0;
 370     rc = sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
 371     assert( rc==SQLITE_OK || pVal==0 );
 372     if( pVal ){
 373       qpvtabStrAppendValue(pStr, pVal);
 374     }
 375     sqlite3_str_append(pStr, "\n", 1);
 376   }
 377   for(i=0; i<pIdxInfo->nConstraint; i++){
 378     int iCol = pIdxInfo->aConstraint[i].iColumn;
 379     int op = pIdxInfo->aConstraint[i].op;
 380     if( op==SQLITE_INDEX_CONSTRAINT_LIMIT
 381      || op==SQLITE_INDEX_CONSTRAINT_OFFSET
 382     ){
 383       iCol = QPVTAB_NONE;
 384     }
 385     if( iCol>=QPVTAB_A && pIdxInfo->aConstraint[i].usable ){
 386       pIdxInfo->aConstraintUsage[i].argvIndex = ++k;
 387       if( iCol<=QPVTAB_FLAGS || (pIdxInfo->idxNum & 0x004)!=0 ){
 388         pIdxInfo->aConstraintUsage[i].omit = 1;
 389       }
 390     }
 391   }
 392   sqlite3_str_appendf(pStr, "nOrderBy,%d,,,,\n", pIdxInfo->nOrderBy);
 393   for(i=0; i<pIdxInfo->nOrderBy; i++){
 394     int iCol = pIdxInfo->aOrderBy[i].iColumn;
 395     sqlite3_str_appendf(pStr, "aOrderBy,%d,%s,%d,,\n",i,
 396       iCol>=0 ? azColname[iCol] : "rowid",
 397       pIdxInfo->aOrderBy[i].desc
 398     );
 399   }
 400   sqlite3_str_appendf(pStr, "sqlite3_vtab_distinct,%d,,,,\n",
 401                       sqlite3_vtab_distinct(pIdxInfo));
 402   sqlite3_str_appendf(pStr, "idxFlags,%d,,,,\n", pIdxInfo->idxFlags);
 403   sqlite3_str_appendf(pStr, "colUsed,%d,,,,\n", (int)pIdxInfo->colUsed);
 404   pIdxInfo->estimatedCost = (double)10;
 405   pIdxInfo->estimatedRows = 10;
 406   sqlite3_str_appendf(pStr, "idxNum,%d,,,,\n", pIdxInfo->idxNum);
 407   sqlite3_str_appendf(pStr, "orderByConsumed,%d,,,,\n",
 408                       pIdxInfo->orderByConsumed);
 409   pIdxInfo->idxStr = sqlite3_str_finish(pStr);
 410   pIdxInfo->needToFreeIdxStr = 1;
 411   return SQLITE_OK;
 412 }
 413
 414 /*
 415 ** This following structure defines all the methods for the
 416 ** virtual table.
 417 */
 418 static sqlite3_module qpvtabModule = {
 419   /* iVersion    */ 0,
 420   /* xCreate     */ 0,
 421   /* xConnect    */ qpvtabConnect,
 422   /* xBestIndex  */ qpvtabBestIndex,
 423   /* xDisconnect */ qpvtabDisconnect,
 424   /* xDestroy    */ 0,
 425   /* xOpen       */ qpvtabOpen,
 426   /* xClose      */ qpvtabClose,
 427   /* xFilter     */ qpvtabFilter,
 428   /* xNext       */ qpvtabNext,
 429   /* xEof        */ qpvtabEof,
 430   /* xColumn     */ qpvtabColumn,
 431   /* xRowid      */ qpvtabRowid,
 432   /* xUpdate     */ 0,
 433   /* xBegin      */ 0,
 434   /* xSync       */ 0,
 435   /* xCommit     */ 0,
 436   /* xRollback   */ 0,
 437   /* xFindMethod */ 0,
 438   /* xRename     */ 0,
 439   /* xSavepoint  */ 0,
 440   /* xRelease    */ 0,
 441   /* xRollbackTo */ 0,
 442   /* xShadowName */ 0,
 443   /* xIntegrity  */ 0
 444 };
 445 #endif /* SQLITE_OMIT_VIRTUALTABLE */
 446
 447
 448 #ifdef _WIN32
 449 __declspec(dllexport)
 450 #endif
 451 int sqlite3_qpvtab_init(
 452   sqlite3 *db,
 453   char **pzErrMsg,
 454   const sqlite3_api_routines *pApi
 455 ){
 456   int rc = SQLITE_OK;
 457   SQLITE_EXTENSION_INIT2(pApi);
 458 #ifndef SQLITE_OMIT_VIRTUALTABLE
 459   rc = sqlite3_create_module(db, "qpvtab", &qpvtabModule, 0);
 460 #endif
 461   return rc;
 462 }