432 lines
12 KiB
C
432 lines
12 KiB
C
/*
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** 2022-01-19
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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**
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** This file implements a virtual-table that returns information about
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** how the query planner called the xBestIndex method. This virtual table
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** is intended for testing and debugging only.
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**
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** The schema of the virtual table is this:
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**
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** CREATE TABLE qpvtab(
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** vn TEXT, -- Name of an sqlite3_index_info field
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** ix INTEGER, -- Array index or value
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** cn TEXT, -- Column name
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** op INTEGER, -- operator
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** ux BOOLEAN, -- "usable" field
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** rhs TEXT, -- sqlite3_vtab_rhs_value()
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**
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** a, b, c, d, e, -- Extra columns to attach constraints to
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**
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** flags INTEGER HIDDEN -- control flags
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** );
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**
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** The virtual table returns a description of the sqlite3_index_info object
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** that was provided to the (successful) xBestIndex method. There is one
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** row in the result table for each field in the sqlite3_index_info object.
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**
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** The values of the "a" through "e" columns are one of:
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**
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** 1. TEXT - the same as the column name
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** 2. INTEGER - 1 for "a", 2 for "b", and so forth
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**
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** Option 1 is the default behavior. 2 is use if there is a usable
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** constraint on "flags" with an integer right-hand side that where the
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** value of the right-hand side has its 0x01 bit set.
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**
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** All constraints on columns "a" through "e" are marked as "omit".
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**
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** If there is a usable constraint on "flags" that has a RHS value that
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** is an integer and that integer has its 0x02 bit set, then the
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** orderByConsumed flag is set.
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**
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** COMPILE:
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**
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** gcc -Wall -g -shared -fPIC -I. qpvtab.c -o qqvtab.so
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**
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** EXAMPLE USAGE:
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**
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** .load ./qpvtab
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** SELECT rowid, *, flags FROM qpvtab(102)
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** WHERE a=19
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** AND b BETWEEN 4.5 and 'hello'
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** AND c<>x'aabbcc'
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** ORDER BY d, e DESC;
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*/
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#if !defined(SQLITEINT_H)
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#include "sqlite3ext.h"
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#endif
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SQLITE_EXTENSION_INIT1
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#include <string.h>
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#include <assert.h>
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#include <stdlib.h>
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#if !defined(SQLITE_OMIT_VIRTUALTABLE)
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/* qpvtab_vtab is a subclass of sqlite3_vtab which is
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** underlying representation of the virtual table
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*/
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typedef struct qpvtab_vtab qpvtab_vtab;
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struct qpvtab_vtab {
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sqlite3_vtab base; /* Base class - must be first */
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};
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/* qpvtab_cursor is a subclass of sqlite3_vtab_cursor which will
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** serve as the underlying representation of a cursor that scans
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** over rows of the result
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*/
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typedef struct qpvtab_cursor qpvtab_cursor;
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struct qpvtab_cursor {
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sqlite3_vtab_cursor base; /* Base class - must be first */
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sqlite3_int64 iRowid; /* The rowid */
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const char *zData; /* Data to return */
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int nData; /* Number of bytes of data */
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int flags; /* Flags value */
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};
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/*
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** Names of columns
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*/
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static const char *azColname[] = {
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"vn",
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"ix",
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"cn",
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"op",
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"ux",
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"rhs",
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"a", "b", "c", "d", "e",
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"flags"
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};
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/*
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** The qpvtabConnect() method is invoked to create a new
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** qpvtab virtual table.
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*/
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static int qpvtabConnect(
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sqlite3 *db,
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void *pAux,
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int argc, const char *const*argv,
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sqlite3_vtab **ppVtab,
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char **pzErr
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){
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qpvtab_vtab *pNew;
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int rc;
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rc = sqlite3_declare_vtab(db,
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"CREATE TABLE x("
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" vn TEXT,"
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" ix INT,"
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" cn TEXT,"
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" op INT,"
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" ux BOOLEAN,"
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" rhs TEXT,"
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" a, b, c, d, e,"
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" flags INT HIDDEN)"
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);
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#define QPVTAB_VN 0
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#define QPVTAB_IX 1
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#define QPVTAB_CN 2
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#define QPVTAB_OP 3
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#define QPVTAB_UX 4
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#define QPVTAB_RHS 5
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#define QPVTAB_A 6
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#define QPVTAB_B 7
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#define QPVTAB_C 8
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#define QPVTAB_D 9
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#define QPVTAB_E 10
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#define QPVTAB_FLAGS 11
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if( rc==SQLITE_OK ){
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pNew = sqlite3_malloc( sizeof(*pNew) );
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*ppVtab = (sqlite3_vtab*)pNew;
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if( pNew==0 ) return SQLITE_NOMEM;
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memset(pNew, 0, sizeof(*pNew));
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}
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return rc;
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}
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/*
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** This method is the destructor for qpvtab_vtab objects.
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*/
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static int qpvtabDisconnect(sqlite3_vtab *pVtab){
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qpvtab_vtab *p = (qpvtab_vtab*)pVtab;
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sqlite3_free(p);
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return SQLITE_OK;
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}
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/*
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** Constructor for a new qpvtab_cursor object.
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*/
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static int qpvtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
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qpvtab_cursor *pCur;
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pCur = sqlite3_malloc( sizeof(*pCur) );
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if( pCur==0 ) return SQLITE_NOMEM;
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memset(pCur, 0, sizeof(*pCur));
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*ppCursor = &pCur->base;
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return SQLITE_OK;
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}
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/*
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** Destructor for a qpvtab_cursor.
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*/
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static int qpvtabClose(sqlite3_vtab_cursor *cur){
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qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
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sqlite3_free(pCur);
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return SQLITE_OK;
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}
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/*
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** Advance a qpvtab_cursor to its next row of output.
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*/
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static int qpvtabNext(sqlite3_vtab_cursor *cur){
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qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
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if( pCur->iRowid<pCur->nData ){
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const char *z = &pCur->zData[pCur->iRowid];
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const char *zEnd = strchr(z, '\n');
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if( zEnd ) zEnd++;
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pCur->iRowid = (int)(zEnd - pCur->zData);
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}
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return SQLITE_OK;
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}
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/*
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** Return values of columns for the row at which the qpvtab_cursor
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** is currently pointing.
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*/
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static int qpvtabColumn(
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sqlite3_vtab_cursor *cur, /* The cursor */
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sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
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int i /* Which column to return */
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){
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qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
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if( i>=QPVTAB_VN && i<=QPVTAB_RHS && pCur->iRowid<pCur->nData ){
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const char *z = &pCur->zData[pCur->iRowid];
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const char *zEnd;
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int j;
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j = QPVTAB_VN;
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while(1){
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zEnd = strchr(z, j==QPVTAB_RHS ? '\n' : ',');
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if( j==i || zEnd==0 ) break;
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z = zEnd+1;
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j++;
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}
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if( zEnd==z ){
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sqlite3_result_null(ctx);
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}else if( i==QPVTAB_IX || i==QPVTAB_OP || i==QPVTAB_UX ){
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sqlite3_result_int(ctx, atoi(z));
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}else{
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sqlite3_result_text64(ctx, z, zEnd-z, SQLITE_TRANSIENT, SQLITE_UTF8);
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}
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}else if( i>=QPVTAB_A && i<=QPVTAB_E ){
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if( pCur->flags & 1 ){
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sqlite3_result_int(ctx, i-QPVTAB_A+1);
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}else{
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char x = 'a'+i-QPVTAB_A;
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sqlite3_result_text64(ctx, &x, 1, SQLITE_TRANSIENT, SQLITE_UTF8);
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}
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}else if( i==QPVTAB_FLAGS ){
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sqlite3_result_int(ctx, pCur->flags);
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}
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return SQLITE_OK;
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}
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/*
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** Return the rowid for the current row. In this implementation, the
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** rowid is the same as the output value.
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*/
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static int qpvtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
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qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
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*pRowid = pCur->iRowid;
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return SQLITE_OK;
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}
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/*
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** Return TRUE if the cursor has been moved off of the last
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** row of output.
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*/
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static int qpvtabEof(sqlite3_vtab_cursor *cur){
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qpvtab_cursor *pCur = (qpvtab_cursor*)cur;
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return pCur->iRowid>=pCur->nData;
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}
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/*
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** This method is called to "rewind" the qpvtab_cursor object back
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** to the first row of output. This method is always called at least
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** once prior to any call to qpvtabColumn() or qpvtabRowid() or
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** qpvtabEof().
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*/
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static int qpvtabFilter(
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sqlite3_vtab_cursor *pVtabCursor,
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int idxNum, const char *idxStr,
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int argc, sqlite3_value **argv
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){
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qpvtab_cursor *pCur = (qpvtab_cursor *)pVtabCursor;
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pCur->iRowid = 0;
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pCur->zData = idxStr;
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pCur->nData = (int)strlen(idxStr);
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pCur->flags = idxNum;
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return SQLITE_OK;
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}
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/*
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** Append the text of a value to pStr
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*/
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static void qpvtabStrAppendValue(
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sqlite3_str *pStr,
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sqlite3_value *pVal
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){
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switch( sqlite3_value_type(pVal) ){
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case SQLITE_NULL:
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sqlite3_str_appendf(pStr, "NULL");
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break;
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case SQLITE_INTEGER:
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sqlite3_str_appendf(pStr, "%lld", sqlite3_value_int64(pVal));
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break;
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case SQLITE_FLOAT:
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sqlite3_str_appendf(pStr, "%!f", sqlite3_value_double(pVal));
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break;
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case SQLITE_TEXT: {
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int i;
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const char *a = (const char*)sqlite3_value_text(pVal);
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int n = sqlite3_value_bytes(pVal);
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sqlite3_str_append(pStr, "'", 1);
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for(i=0; i<n; i++){
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char c = a[i];
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if( c=='\n' ) c = ' ';
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sqlite3_str_append(pStr, &c, 1);
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if( c=='\'' ) sqlite3_str_append(pStr, &c, 1);
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}
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sqlite3_str_append(pStr, "'", 1);
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break;
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}
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case SQLITE_BLOB: {
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int i;
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const unsigned char *a = sqlite3_value_blob(pVal);
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int n = sqlite3_value_bytes(pVal);
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sqlite3_str_append(pStr, "x'", 2);
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for(i=0; i<n; i++){
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sqlite3_str_appendf(pStr, "%02x", a[i]);
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}
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sqlite3_str_append(pStr, "'", 1);
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break;
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}
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}
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}
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/*
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** SQLite will invoke this method one or more times while planning a query
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** that uses the virtual table. This routine needs to create
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** a query plan for each invocation and compute an estimated cost for that
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** plan.
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*/
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static int qpvtabBestIndex(
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sqlite3_vtab *tab,
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sqlite3_index_info *pIdxInfo
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){
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sqlite3_str *pStr = sqlite3_str_new(0);
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int i, k = 0;
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sqlite3_str_appendf(pStr, "nConstraint,%d,,,,\n", pIdxInfo->nConstraint);
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for(i=0; i<pIdxInfo->nConstraint; i++){
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sqlite3_value *pVal;
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int iCol = pIdxInfo->aConstraint[i].iColumn;
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if( iCol==QPVTAB_FLAGS && pIdxInfo->aConstraint[i].usable ){
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pVal = 0;
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sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
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if( pVal ){
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pIdxInfo->idxNum = sqlite3_value_int(pVal);
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if( pIdxInfo->idxNum & 2 ) pIdxInfo->orderByConsumed = 1;
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}
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}
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sqlite3_str_appendf(pStr,"aConstraint,%d,%s,%d,%d,",
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i,
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azColname[iCol],
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pIdxInfo->aConstraint[i].op,
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pIdxInfo->aConstraint[i].usable);
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pVal = 0;
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sqlite3_vtab_rhs_value(pIdxInfo, i, &pVal);
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if( pVal ){
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qpvtabStrAppendValue(pStr, pVal);
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}
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sqlite3_str_append(pStr, "\n", 1);
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if( iCol>=QPVTAB_A && pIdxInfo->aConstraint[i].usable ){
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pIdxInfo->aConstraintUsage[i].argvIndex = ++k;
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pIdxInfo->aConstraintUsage[i].omit = 1;
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}
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}
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sqlite3_str_appendf(pStr, "nOrderBy,%d,,,,\n", pIdxInfo->nOrderBy);
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for(i=0; i<pIdxInfo->nOrderBy; i++){
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int iCol = pIdxInfo->aOrderBy[i].iColumn;
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sqlite3_str_appendf(pStr, "aOrderBy,%d,%s,%d,,\n",i,
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iCol>=0 ? azColname[iCol] : "rowid",
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pIdxInfo->aOrderBy[i].desc
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);
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}
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sqlite3_str_appendf(pStr, "idxFlags,%d,,,,\n", pIdxInfo->idxFlags);
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sqlite3_str_appendf(pStr, "colUsed,%d,,,,\n", (int)pIdxInfo->colUsed);
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pIdxInfo->estimatedCost = (double)10;
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pIdxInfo->estimatedRows = 10;
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sqlite3_str_appendf(pStr, "idxNum,%d,,,,\n", pIdxInfo->idxNum);
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sqlite3_str_appendf(pStr, "orderByConsumed,%d,,,,\n",
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pIdxInfo->orderByConsumed);
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pIdxInfo->idxStr = sqlite3_str_finish(pStr);
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pIdxInfo->needToFreeIdxStr = 1;
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return SQLITE_OK;
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}
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/*
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** This following structure defines all the methods for the
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** virtual table.
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*/
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static sqlite3_module qpvtabModule = {
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/* iVersion */ 0,
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/* xCreate */ 0,
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/* xConnect */ qpvtabConnect,
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/* xBestIndex */ qpvtabBestIndex,
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/* xDisconnect */ qpvtabDisconnect,
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/* xDestroy */ 0,
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/* xOpen */ qpvtabOpen,
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/* xClose */ qpvtabClose,
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/* xFilter */ qpvtabFilter,
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/* xNext */ qpvtabNext,
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/* xEof */ qpvtabEof,
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/* xColumn */ qpvtabColumn,
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/* xRowid */ qpvtabRowid,
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/* xUpdate */ 0,
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/* xBegin */ 0,
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/* xSync */ 0,
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/* xCommit */ 0,
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/* xRollback */ 0,
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/* xFindMethod */ 0,
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/* xRename */ 0,
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/* xSavepoint */ 0,
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/* xRelease */ 0,
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/* xRollbackTo */ 0,
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/* xShadowName */ 0
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};
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#endif /* SQLITE_OMIT_VIRTUALTABLE */
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#ifdef _WIN32
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__declspec(dllexport)
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#endif
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int sqlite3_qpvtab_init(
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sqlite3 *db,
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char **pzErrMsg,
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const sqlite3_api_routines *pApi
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){
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int rc = SQLITE_OK;
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SQLITE_EXTENSION_INIT2(pApi);
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#ifndef SQLITE_OMIT_VIRTUALTABLE
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rc = sqlite3_create_module(db, "qpvtab", &qpvtabModule, 0);
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#endif
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return rc;
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}
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