mirror of
https://github.com/tursodatabase/libsql.git
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281 lines
7.5 KiB
C
281 lines
7.5 KiB
C
/*
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** 2011 April 02
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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 the whole numbers
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** between 1 and 4294967295, inclusive.
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**
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** Example:
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**
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** CREATE VIRTUAL TABLE nums USING wholenumber;
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** SELECT value FROM nums WHERE value<10;
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**
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** Results in:
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**
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** 1 2 3 4 5 6 7 8 9
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*/
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#include "sqlite3ext.h"
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SQLITE_EXTENSION_INIT1
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#include <assert.h>
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#include <string.h>
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#ifndef SQLITE_OMIT_VIRTUALTABLE
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/* A wholenumber cursor object */
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typedef struct wholenumber_cursor wholenumber_cursor;
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struct wholenumber_cursor {
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sqlite3_vtab_cursor base; /* Base class - must be first */
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sqlite3_int64 iValue; /* Current value */
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sqlite3_int64 mxValue; /* Maximum value */
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};
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/* Methods for the wholenumber module */
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static int wholenumberConnect(
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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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sqlite3_vtab *pNew;
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pNew = *ppVtab = sqlite3_malloc( sizeof(*pNew) );
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if( pNew==0 ) return SQLITE_NOMEM;
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sqlite3_declare_vtab(db, "CREATE TABLE x(value)");
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sqlite3_vtab_config(db, SQLITE_VTAB_INNOCUOUS);
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memset(pNew, 0, sizeof(*pNew));
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return SQLITE_OK;
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}
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/* Note that for this virtual table, the xCreate and xConnect
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** methods are identical. */
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static int wholenumberDisconnect(sqlite3_vtab *pVtab){
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sqlite3_free(pVtab);
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return SQLITE_OK;
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}
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/* The xDisconnect and xDestroy methods are also the same */
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/*
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** Open a new wholenumber cursor.
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*/
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static int wholenumberOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
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wholenumber_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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** Close a wholenumber cursor.
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*/
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static int wholenumberClose(sqlite3_vtab_cursor *cur){
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sqlite3_free(cur);
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return SQLITE_OK;
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}
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/*
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** Advance a cursor to its next row of output
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*/
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static int wholenumberNext(sqlite3_vtab_cursor *cur){
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wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
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pCur->iValue++;
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return SQLITE_OK;
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}
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/*
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** Return the value associated with a wholenumber.
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*/
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static int wholenumberColumn(
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sqlite3_vtab_cursor *cur,
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sqlite3_context *ctx,
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int i
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){
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wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
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sqlite3_result_int64(ctx, pCur->iValue);
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return SQLITE_OK;
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}
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/*
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** The rowid.
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*/
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static int wholenumberRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
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wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
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*pRowid = pCur->iValue;
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return SQLITE_OK;
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}
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/*
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** When the wholenumber_cursor.rLimit value is 0 or less, that is a signal
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** that the cursor has nothing more to output.
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*/
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static int wholenumberEof(sqlite3_vtab_cursor *cur){
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wholenumber_cursor *pCur = (wholenumber_cursor*)cur;
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return pCur->iValue>pCur->mxValue || pCur->iValue==0;
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}
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/*
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** Called to "rewind" a cursor back to the beginning so that
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** it starts its output over again. Always called at least once
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** prior to any wholenumberColumn, wholenumberRowid, or wholenumberEof call.
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**
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** idxNum Constraints
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** ------ ---------------------
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** 0 (none)
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** 1 value > $argv0
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** 2 value >= $argv0
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** 4 value < $argv0
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** 8 value <= $argv0
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**
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** 5 value > $argv0 AND value < $argv1
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** 6 value >= $argv0 AND value < $argv1
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** 9 value > $argv0 AND value <= $argv1
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** 10 value >= $argv0 AND value <= $argv1
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*/
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static int wholenumberFilter(
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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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wholenumber_cursor *pCur = (wholenumber_cursor *)pVtabCursor;
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sqlite3_int64 v;
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int i = 0;
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pCur->iValue = 1;
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pCur->mxValue = 0xffffffff; /* 4294967295 */
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if( idxNum & 3 ){
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v = sqlite3_value_int64(argv[0]) + (idxNum&1);
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if( v>pCur->iValue && v<=pCur->mxValue ) pCur->iValue = v;
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i++;
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}
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if( idxNum & 12 ){
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v = sqlite3_value_int64(argv[i]) - ((idxNum>>2)&1);
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if( v>=pCur->iValue && v<pCur->mxValue ) pCur->mxValue = v;
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}
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return SQLITE_OK;
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}
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/*
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** Search for terms of these forms:
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**
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** (1) value > $value
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** (2) value >= $value
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** (4) value < $value
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** (8) value <= $value
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**
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** idxNum is an ORed combination of 1 or 2 with 4 or 8.
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*/
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static int wholenumberBestIndex(
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sqlite3_vtab *tab,
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sqlite3_index_info *pIdxInfo
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){
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int i;
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int idxNum = 0;
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int argvIdx = 1;
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int ltIdx = -1;
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int gtIdx = -1;
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const struct sqlite3_index_constraint *pConstraint;
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pConstraint = pIdxInfo->aConstraint;
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for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
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if( pConstraint->usable==0 ) continue;
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if( (idxNum & 3)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_GT ){
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idxNum |= 1;
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ltIdx = i;
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}
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if( (idxNum & 3)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_GE ){
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idxNum |= 2;
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ltIdx = i;
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}
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if( (idxNum & 12)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_LT ){
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idxNum |= 4;
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gtIdx = i;
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}
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if( (idxNum & 12)==0 && pConstraint->op==SQLITE_INDEX_CONSTRAINT_LE ){
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idxNum |= 8;
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gtIdx = i;
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}
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}
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pIdxInfo->idxNum = idxNum;
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if( ltIdx>=0 ){
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pIdxInfo->aConstraintUsage[ltIdx].argvIndex = argvIdx++;
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pIdxInfo->aConstraintUsage[ltIdx].omit = 1;
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}
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if( gtIdx>=0 ){
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pIdxInfo->aConstraintUsage[gtIdx].argvIndex = argvIdx;
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pIdxInfo->aConstraintUsage[gtIdx].omit = 1;
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}
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if( pIdxInfo->nOrderBy==1
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&& pIdxInfo->aOrderBy[0].desc==0
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){
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pIdxInfo->orderByConsumed = 1;
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}
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if( (idxNum & 12)==0 ){
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pIdxInfo->estimatedCost = 1e99;
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}else if( (idxNum & 3)==0 ){
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pIdxInfo->estimatedCost = (double)5;
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}else{
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pIdxInfo->estimatedCost = (double)1;
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}
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return SQLITE_OK;
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}
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/*
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** A virtual table module that provides read-only access to a
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** Tcl global variable namespace.
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*/
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static sqlite3_module wholenumberModule = {
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0, /* iVersion */
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wholenumberConnect,
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wholenumberConnect,
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wholenumberBestIndex,
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wholenumberDisconnect,
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wholenumberDisconnect,
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wholenumberOpen, /* xOpen - open a cursor */
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wholenumberClose, /* xClose - close a cursor */
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wholenumberFilter, /* xFilter - configure scan constraints */
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wholenumberNext, /* xNext - advance a cursor */
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wholenumberEof, /* xEof - check for end of scan */
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wholenumberColumn, /* xColumn - read data */
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wholenumberRowid, /* xRowid - read data */
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0, /* xUpdate */
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0, /* xBegin */
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0, /* xSync */
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0, /* xCommit */
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0, /* xRollback */
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0, /* xFindMethod */
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0, /* xRename */
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0, /* xSavepoint */
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0, /* xRelease */
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0, /* xRollbackTo */
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0, /* xShadowName */
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0 /* xIntegrity */
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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_wholenumber_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, "wholenumber", &wholenumberModule, 0);
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#endif
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return rc;
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}
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