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Initial implementation of the sqlite3_vtab_rhs_value() interface and the

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qpvtab extension used for testing the virtual table interface.

FossilOrigin-Name: 0873c76b9b96b66fa9d13ddc8bca126d575ea3352349c7fd648f0c2f75d770f5
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drh
2022-01-20 17:10:59 +00:00
parent f208abdd99
commit 82801a5b72
11 changed files with 446 additions and 21 deletions
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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(a,b,c,d,e, f,g,h,i,j, k,l,m,n,o, p,q,r,s,t);
**
** There is also a HIDDEN column "flags".
**
** All columns except column "a" have a value that is either TEXT that
** is there name, or INTEGER which is their index (b==1). TEXT is the
** default, but INTEGER is used of there is a constraint on flags where the
** right-hand side is an integer that includes the 1 bit.
**
** The "a" column returns text that describes one of the parameters that
** xBestIndex was called with. A completely query of the table should
** show all details of how xBestIndex was called.
*/
#if !defined(SQLITEINT_H)
#include "sqlite3ext.h"
#endif
SQLITE_EXTENSION_INIT1
#include <string.h>
#include <assert.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 */
};
/*
** 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(a,b,c,d,e, f,g,h,i,j, k,l,m,n,o, p,q,r,s,t,"
" flags HIDDEN)"
);
#define QPVTAB_A 0
#define QPVTAB_B 1
#define QPVTAB_T 19
#define QPVTAB_FLAGS 20
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;
while( pCur->iRowid<pCur->nData && pCur->zData[pCur->iRowid]!='\n' ){
pCur->iRowid++;
}
if( pCur->zData[pCur->iRowid]=='\n' ) pCur->iRowid++;
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==0 && pCur->iRowid<pCur->nData ){
int j;
for(j=pCur->iRowid; j<pCur->nData && pCur->zData[j]!='\n'; j++){}
sqlite3_result_text64(ctx, &pCur->zData[pCur->iRowid], j-pCur->iRowid,
SQLITE_TRANSIENT, SQLITE_UTF8);
}else if( i>=QPVTAB_B && i<=QPVTAB_T ){
if( pCur->flags & 1 ){
sqlite3_result_int(ctx, i);
}else{
char x = 'a'+i;
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:
sqlite3_str_appendf(pStr, "%Q", sqlite3_value_text(pVal));
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;
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;
char zCol[8];
if( iCol==QPVTAB_FLAGS ){
strcpy(zCol, "flags");
if( pIdxInfo->aConstraint[i].usable ){
pVal = 0;
sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
if( pVal ){
pIdxInfo->idxNum = sqlite3_value_int(pVal);
}
}
}else{
zCol[0] = iCol+'a';
zCol[1] = 0;
}
sqlite3_str_appendf(pStr,"aConstraint[%d]: iColumn=%s op=%d usable=%d",
i,
zCol,
pIdxInfo->aConstraint[i].op,
pIdxInfo->aConstraint[i].usable);
pVal = 0;
sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
if( pVal ){
sqlite3_str_appendf(pStr, " value=");
qpvtabStrAppendValue(pStr, pVal);
}
sqlite3_str_append(pStr, "\n", 1);
if( pIdxInfo->aConstraint[i].usable ){
pIdxInfo->aConstraintUsage[i].argvIndex = ++k;
pIdxInfo->aConstraintUsage[i].omit = 1;
}
}
pIdxInfo->estimatedCost = (double)10;
pIdxInfo->estimatedRows = 10;
sqlite3_str_appendf(pStr, "idxNum=%d\n", pIdxInfo->idxNum);
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;
}