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 */
qpvtabConnect(sqlite3 * db,void * pAux,int argc,const char * const * argv,sqlite3_vtab ** ppVtab,char ** pzErr)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 */
qpvtabDisconnect(sqlite3_vtab * pVtab)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 */
qpvtabOpen(sqlite3_vtab * p,sqlite3_vtab_cursor ** ppCursor)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 */
qpvtabClose(sqlite3_vtab_cursor * cur)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 */
qpvtabNext(sqlite3_vtab_cursor * cur)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 */
qpvtabColumn(sqlite3_vtab_cursor * cur,sqlite3_context * ctx,int i)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 */
qpvtabRowid(sqlite3_vtab_cursor * cur,sqlite_int64 * pRowid)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 */
qpvtabEof(sqlite3_vtab_cursor * cur)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 */
qpvtabFilter(sqlite3_vtab_cursor * pVtabCursor,int idxNum,const char * idxStr,int argc,sqlite3_value ** argv)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 */
qpvtabStrAppendValue(sqlite3_str * pStr,sqlite3_value * pVal)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 */
qpvtabBestIndex(sqlite3_vtab * tab,sqlite3_index_info * pIdxInfo)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 };
444 #endif /* SQLITE_OMIT_VIRTUALTABLE */
445
446
447 #ifdef _WIN32
448 __declspec(dllexport)
449 #endif
sqlite3_qpvtab_init(sqlite3 * db,char ** pzErrMsg,const sqlite3_api_routines * pApi)450 int sqlite3_qpvtab_init(
451 sqlite3 *db,
452 char **pzErrMsg,
453 const sqlite3_api_routines *pApi
454 ){
455 int rc = SQLITE_OK;
456 SQLITE_EXTENSION_INIT2(pApi);
457 #ifndef SQLITE_OMIT_VIRTUALTABLE
458 rc = sqlite3_create_module(db, "qpvtab", &qpvtabModule, 0);
459 #endif
460 return rc;
461 }
462