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sqlite/ext/misc/qpvtab.c
drh 8f2c0b59da Query planner always honors the aConstraintUsage[].omit flag for the 
SQLITE_INDEX_CONSTRAINT_OFFSET constraint.

FossilOrigin-Name: 38c5151eb8cc789ad082a1b40d16b2ddb55454219bd685b6e420995af6a15f55
2022-01-27 21:18:14 +00:00

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/*
** 2022-01-19
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file implements a virtual-table that returns information about
** how the query planner called the xBestIndex method. This virtual table
** is intended for testing and debugging only.
**
** The schema of the virtual table is this:
**
** CREATE TABLE qpvtab(
** vn TEXT, -- Name of an sqlite3_index_info field
** ix INTEGER, -- Array index or value
** cn TEXT, -- Column name
** op INTEGER, -- operator
** ux BOOLEAN, -- "usable" field
** rhs TEXT, -- sqlite3_vtab_rhs_value()
**
** a, b, c, d, e, -- Extra columns to attach constraints to
**
** flags INTEGER HIDDEN -- control flags
** );
**
** The virtual table returns a description of the sqlite3_index_info object
** that was provided to the (successful) xBestIndex method. There is one
** row in the result table for each field in the sqlite3_index_info object.
**
** The values of the "a" through "e" columns are one of:
**
** 1. TEXT - the same as the column name
** 2. INTEGER - 1 for "a", 2 for "b", and so forth
**
** Option 1 is the default behavior. 2 is use if there is a usable
** constraint on "flags" with an integer right-hand side that where the
** value of the right-hand side has its 0x001 bit set.
**
** All constraints on columns "a" through "e" are marked as "omit".
**
** If there is a usable constraint on "flags" that has a RHS value that
** is an integer and that integer has its 0x02 bit set, then the
** orderByConsumed flag is set.
**
** FLAGS SUMMARY:
**
** 0x001 Columns 'a' through 'e' have INT values
** 0x002 orderByConsumed is set
** 0x004 OFFSET and LIMIT have omit set
**
** COMPILE:
**
** gcc -Wall -g -shared -fPIC -I. qpvtab.c -o qqvtab.so
**
** EXAMPLE USAGE:
**
** .load ./qpvtab
** SELECT rowid, *, flags FROM qpvtab(102)
** WHERE a=19
** AND b BETWEEN 4.5 and 'hello'
** AND c<>x'aabbcc'
** ORDER BY d, e DESC;
*/
#if !defined(SQLITEINT_H)
#include "sqlite3ext.h"
#endif
SQLITE_EXTENSION_INIT1
#include <string.h>
#include <assert.h>
#include <stdlib.h>
#if !defined(SQLITE_OMIT_VIRTUALTABLE)
/* qpvtab_vtab is a subclass of sqlite3_vtab which is
** underlying representation of the virtual table
*/
typedef struct qpvtab_vtab qpvtab_vtab;
struct qpvtab_vtab {
sqlite3_vtab base; /* Base class - must be first */
};
/* qpvtab_cursor is a subclass of sqlite3_vtab_cursor which will
** serve as the underlying representation of a cursor that scans
** over rows of the result
*/
typedef struct qpvtab_cursor qpvtab_cursor;
struct qpvtab_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3_int64 iRowid; /* The rowid */
const char *zData; /* Data to return */
int nData; /* Number of bytes of data */
int flags; /* Flags value */
};
/*
** Names of columns
*/
static const char *azColname[] = {
"vn",
"ix",
"cn",
"op",
"ux",
"rhs",
"a", "b", "c", "d", "e",
"flags",
""
};
/*
** The qpvtabConnect() method is invoked to create a new
** qpvtab virtual table.
*/
static int qpvtabConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
qpvtab_vtab *pNew;
int rc;
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x("
" vn TEXT,"
" ix INT,"
" cn TEXT,"
" op INT,"
" ux BOOLEAN,"
" rhs TEXT,"
" a, b, c, d, e,"
" flags INT HIDDEN)"
);
#define QPVTAB_VN 0
#define QPVTAB_IX 1
#define QPVTAB_CN 2
#define QPVTAB_OP 3
#define QPVTAB_UX 4
#define QPVTAB_RHS 5
#define QPVTAB_A 6
#define QPVTAB_B 7
#define QPVTAB_C 8
#define QPVTAB_D 9
#define QPVTAB_E 10
#define QPVTAB_FLAGS 11
#define QPVTAB_NONE 12
if( rc==SQLITE_OK ){
pNew = sqlite3_malloc( sizeof(*pNew) );
*ppVtab = (sqlite3_vtab*)pNew;
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(*pNew));
}
return rc;
}
/*
** This method is the destructor for qpvtab_vtab objects.
*/
static int qpvtabDisconnect(sqlite3_vtab *pVtab){
qpvtab_vtab *p = (qpvtab_vtab*)pVtab;
sqlite3_free(p);
return SQLITE_OK;
}
/*
** Constructor for a new qpvtab_cursor object.
*/
static int qpvtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
qpvtab_cursor *pCur;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
*ppCursor = &pCur->base;
return SQLITE_OK;
}
/*
** Destructor for a qpvtab_cursor.
*/
static int qpvtabClose(sqlite3_vtab_cursor *cur){
qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
sqlite3_free(pCur);
return SQLITE_OK;
}
/*
** Advance a qpvtab_cursor to its next row of output.
*/
static int qpvtabNext(sqlite3_vtab_cursor *cur){
qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
if( pCur->iRowid<pCur->nData ){
const char *z = &pCur->zData[pCur->iRowid];
const char *zEnd = strchr(z, '\n');
if( zEnd ) zEnd++;
pCur->iRowid = (int)(zEnd - pCur->zData);
}
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the qpvtab_cursor
** is currently pointing.
*/
static int qpvtabColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int i /* Which column to return */
){
qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
if( i>=QPVTAB_VN && i<=QPVTAB_RHS && pCur->iRowid<pCur->nData ){
const char *z = &pCur->zData[pCur->iRowid];
const char *zEnd;
int j;
j = QPVTAB_VN;
while(1){
zEnd = strchr(z, j==QPVTAB_RHS ? '\n' : ',');
if( j==i || zEnd==0 ) break;
z = zEnd+1;
j++;
}
if( zEnd==z ){
sqlite3_result_null(ctx);
}else if( i==QPVTAB_IX || i==QPVTAB_OP || i==QPVTAB_UX ){
sqlite3_result_int(ctx, atoi(z));
}else{
sqlite3_result_text64(ctx, z, zEnd-z, SQLITE_TRANSIENT, SQLITE_UTF8);
}
}else if( i>=QPVTAB_A && i<=QPVTAB_E ){
if( pCur->flags & 0x001 ){
sqlite3_result_int(ctx, i-QPVTAB_A+1);
}else{
char x = 'a'+i-QPVTAB_A;
sqlite3_result_text64(ctx, &x, 1, SQLITE_TRANSIENT, SQLITE_UTF8);
}
}else if( i==QPVTAB_FLAGS ){
sqlite3_result_int(ctx, pCur->flags);
}
return SQLITE_OK;
}
/*
** Return the rowid for the current row. In this implementation, the
** rowid is the same as the output value.
*/
static int qpvtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
*pRowid = pCur->iRowid;
return SQLITE_OK;
}
/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int qpvtabEof(sqlite3_vtab_cursor *cur){
qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
return pCur->iRowid>=pCur->nData;
}
/*
** This method is called to "rewind" the qpvtab_cursor object back
** to the first row of output. This method is always called at least
** once prior to any call to qpvtabColumn() or qpvtabRowid() or
** qpvtabEof().
*/
static int qpvtabFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
qpvtab_cursor *pCur = (qpvtab_cursor *)pVtabCursor;
pCur->iRowid = 0;
pCur->zData = idxStr;
pCur->nData = (int)strlen(idxStr);
pCur->flags = idxNum;
return SQLITE_OK;
}
/*
** Append the text of a value to pStr
*/
static void qpvtabStrAppendValue(
sqlite3_str *pStr,
sqlite3_value *pVal
){
switch( sqlite3_value_type(pVal) ){
case SQLITE_NULL:
sqlite3_str_appendf(pStr, "NULL");
break;
case SQLITE_INTEGER:
sqlite3_str_appendf(pStr, "%lld", sqlite3_value_int64(pVal));
break;
case SQLITE_FLOAT:
sqlite3_str_appendf(pStr, "%!f", sqlite3_value_double(pVal));
break;
case SQLITE_TEXT: {
int i;
const char *a = (const char*)sqlite3_value_text(pVal);
int n = sqlite3_value_bytes(pVal);
sqlite3_str_append(pStr, "'", 1);
for(i=0; i<n; i++){
char c = a[i];
if( c=='\n' ) c = ' ';
sqlite3_str_append(pStr, &c, 1);
if( c=='\'' ) sqlite3_str_append(pStr, &c, 1);
}
sqlite3_str_append(pStr, "'", 1);
break;
}
case SQLITE_BLOB: {
int i;
const unsigned char *a = sqlite3_value_blob(pVal);
int n = sqlite3_value_bytes(pVal);
sqlite3_str_append(pStr, "x'", 2);
for(i=0; i<n; i++){
sqlite3_str_appendf(pStr, "%02x", a[i]);
}
sqlite3_str_append(pStr, "'", 1);
break;
}
}
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
*/
static int qpvtabBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
sqlite3_str *pStr = sqlite3_str_new(0);
int i, k = 0;
int rc;
sqlite3_str_appendf(pStr, "nConstraint,%d,,,,\n", pIdxInfo->nConstraint);
for(i=0; i<pIdxInfo->nConstraint; i++){
sqlite3_value *pVal;
int iCol = pIdxInfo->aConstraint[i].iColumn;
int op = pIdxInfo->aConstraint[i].op;
if( iCol==QPVTAB_FLAGS && pIdxInfo->aConstraint[i].usable ){
pVal = 0;
rc = sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
assert( rc==SQLITE_OK || pVal==0 );
if( pVal ){
pIdxInfo->idxNum = sqlite3_value_int(pVal);
if( pIdxInfo->idxNum & 0x002 ) pIdxInfo->orderByConsumed = 1;
}
}
if( op==SQLITE_INDEX_CONSTRAINT_LIMIT
|| op==SQLITE_INDEX_CONSTRAINT_OFFSET
){
iCol = QPVTAB_NONE;
}
sqlite3_str_appendf(pStr,"aConstraint,%d,%s,%d,%d,",
i,
azColname[iCol],
op,
pIdxInfo->aConstraint[i].usable);
pVal = 0;
rc = sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
assert( rc==SQLITE_OK || pVal==0 );
if( pVal ){
qpvtabStrAppendValue(pStr, pVal);
}
sqlite3_str_append(pStr, "\n", 1);
}
for(i=0; i<pIdxInfo->nConstraint; i++){
int iCol = pIdxInfo->aConstraint[i].iColumn;
int op = pIdxInfo->aConstraint[i].op;
if( op==SQLITE_INDEX_CONSTRAINT_LIMIT
|| op==SQLITE_INDEX_CONSTRAINT_OFFSET
){
iCol = QPVTAB_NONE;
}
if( iCol>=QPVTAB_A && pIdxInfo->aConstraint[i].usable ){
pIdxInfo->aConstraintUsage[i].argvIndex = ++k;
if( iCol<=QPVTAB_FLAGS || (pIdxInfo->idxNum & 0x004)!=0 ){
pIdxInfo->aConstraintUsage[i].omit = 1;
}
}
}
sqlite3_str_appendf(pStr, "nOrderBy,%d,,,,\n", pIdxInfo->nOrderBy);
for(i=0; i<pIdxInfo->nOrderBy; i++){
int iCol = pIdxInfo->aOrderBy[i].iColumn;
sqlite3_str_appendf(pStr, "aOrderBy,%d,%s,%d,,\n",i,
iCol>=0 ? azColname[iCol] : "rowid",
pIdxInfo->aOrderBy[i].desc
);
}
sqlite3_str_appendf(pStr, "sqlite3_vtab_distinct,%d,,,,\n",
sqlite3_vtab_distinct(pIdxInfo));
sqlite3_str_appendf(pStr, "idxFlags,%d,,,,\n", pIdxInfo->idxFlags);
sqlite3_str_appendf(pStr, "colUsed,%d,,,,\n", (int)pIdxInfo->colUsed);
pIdxInfo->estimatedCost = (double)10;
pIdxInfo->estimatedRows = 10;
sqlite3_str_appendf(pStr, "idxNum,%d,,,,\n", pIdxInfo->idxNum);
sqlite3_str_appendf(pStr, "orderByConsumed,%d,,,,\n",
pIdxInfo->orderByConsumed);
pIdxInfo->idxStr = sqlite3_str_finish(pStr);
pIdxInfo->needToFreeIdxStr = 1;
return SQLITE_OK;
}
/*
** This following structure defines all the methods for the
** virtual table.
*/
static sqlite3_module qpvtabModule = {
/* iVersion */ 0,
/* xCreate */ 0,
/* xConnect */ qpvtabConnect,
/* xBestIndex */ qpvtabBestIndex,
/* xDisconnect */ qpvtabDisconnect,
/* xDestroy */ 0,
/* xOpen */ qpvtabOpen,
/* xClose */ qpvtabClose,
/* xFilter */ qpvtabFilter,
/* xNext */ qpvtabNext,
/* xEof */ qpvtabEof,
/* xColumn */ qpvtabColumn,
/* xRowid */ qpvtabRowid,
/* xUpdate */ 0,
/* xBegin */ 0,
/* xSync */ 0,
/* xCommit */ 0,
/* xRollback */ 0,
/* xFindMethod */ 0,
/* xRename */ 0,
/* xSavepoint */ 0,
/* xRelease */ 0,
/* xRollbackTo */ 0,
/* xShadowName */ 0
};
#endif /* SQLITE_OMIT_VIRTUALTABLE */
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_qpvtab_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3_create_module(db, "qpvtab", &qpvtabModule, 0);
#endif
return rc;
}
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