/*
** 2017 July 15
**
** 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 contains the implementation of the "unionvtab" virtual
** table. This module provides read-only access to multiple tables,
** possibly in multiple database files, via a single database object.
** The source tables must have the following characteristics:
**
** * They must all be rowid tables (not VIRTUAL or WITHOUT ROWID
** tables or views).
**
** * Each table must have the same set of columns, declared in
** the same order and with the same declared types.
**
** * The tables must not feature a user-defined column named "_rowid_".
**
** * Each table must contain a distinct range of rowid values.
**
** A "unionvtab" virtual table is created as follows:
**
** CREATE VIRTUAL TABLE <name> USING unionvtab(<sql statement>);
**
** The implementation evalutes <sql statement> whenever a unionvtab virtual
** table is created or opened. It should return one row for each source
** database table. The four columns required of each row are:
**
** 1. The name of the database containing the table ("main" or "temp" or
** the name of an attached database). Or NULL to indicate that all
** databases should be searched for the table in the usual fashion.
**
** 2. The name of the database table.
**
** 3. The smallest rowid in the range of rowids that may be stored in the
** database table (an integer).
**
** 4. The largest rowid in the range of rowids that may be stored in the
** database table (an integer).
**
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Largest and smallest possible 64-bit signed integers. These macros
** copied from sqliteInt.h.
*/
#ifndef LARGEST_INT64
# define LARGEST_INT64 (0xffffffff|(((sqlite3_int64)0x7fffffff)<<32))
#endif
#ifndef SMALLEST_INT64
# define SMALLEST_INT64 (((sqlite3_int64)-1) - LARGEST_INT64)
#endif
typedef struct UnionCsr UnionCsr;
typedef struct UnionTab UnionTab;
typedef struct UnionSrc UnionSrc;
/*
** Each source table (row returned by the initialization query) is
** represented by an instance of the following structure stored in the
** UnionTab.aSrc[] array.
*/
struct UnionSrc {
char *zDb; /* Database containing source table */
char *zTab; /* Source table name */
sqlite3_int64 iMin; /* Minimum rowid */
sqlite3_int64 iMax; /* Maximum rowid */
};
/*
** Virtual table type for union vtab.
*/
struct UnionTab {
sqlite3_vtab base; /* Base class - must be first */
sqlite3 *db; /* Database handle */
int iPK; /* INTEGER PRIMARY KEY column, or -1 */
int nSrc; /* Number of elements in the aSrc[] array */
UnionSrc *aSrc; /* Array of source tables, sorted by rowid */
};
/*
** Virtual table cursor type for union vtab.
*/
struct UnionCsr {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3_stmt *pStmt; /* SQL statement to run */
};
/*
** If *pRc is other than SQLITE_OK when this function is called, it
** always returns NULL. Otherwise, it attempts to allocate and return
** a pointer to nByte bytes of zeroed memory. If the memory allocation
** is attempted but fails, NULL is returned and *pRc is set to
** SQLITE_NOMEM.
*/
static void *unionMalloc(int *pRc, int nByte){
void *pRet;
assert( nByte>0 );
if( *pRc==SQLITE_OK ){
pRet = sqlite3_malloc(nByte);
if( pRet ){
memset(pRet, 0, nByte);
}else{
*pRc = SQLITE_NOMEM;
}
}else{
pRet = 0;
}
return pRet;
}
/*
** If *pRc is other than SQLITE_OK when this function is called, it
** always returns NULL. Otherwise, it attempts to allocate and return
** a copy of the nul-terminated string passed as the second argument.
** If the allocation is attempted but fails, NULL is returned and *pRc is
** set to SQLITE_NOMEM.
*/
static char *unionStrdup(int *pRc, const char *zIn){
char *zRet = 0;
if( zIn ){
int nByte = (int)strlen(zIn) + 1;
zRet = unionMalloc(pRc, nByte);
if( zRet ){
memcpy(zRet, zIn, nByte);
}
}
return zRet;
}
/*
** If the first character of the string passed as the only argument to this
** function is one of the 4 that may be used as an open quote character
** in SQL, this function assumes that the input is a well-formed quoted SQL
** string. In this case the string is dequoted in place.
**
** If the first character of the input is not an open quote, then this
** function is a no-op.
*/
static void unionDequote(char *z){
if( z ){
char q = z[0];
/* Set stack variable q to the close-quote character */
if( q=='[' || q=='\'' || q=='"' || q=='`' ){
int iIn = 1;
int iOut = 0;
if( q=='[' ) q = ']';
while( z[iIn] ){
if( z[iIn]==q ){
if( z[iIn+1]!=q ){
/* Character iIn was the close quote. */
iIn++;
break;
}else{
/* Character iIn and iIn+1 form an escaped quote character. Skip
** the input cursor past both and copy a single quote character
** to the output buffer. */
iIn += 2;
z[iOut++] = q;
}
}else{
z[iOut++] = z[iIn++];
}
}
z[iOut] = '\0';
}
}
}
/*
** This function is a no-op if *pRc is set to other than SQLITE_OK when it
** is called. NULL is returned in this case.
**
** Otherwise, the SQL statement passed as the third argument is prepared
** against the database handle passed as the second. If the statement is
** successfully prepared, a pointer to the new statement handle is
** returned. It is the responsibility of the caller to eventually free the
** statement by calling sqlite3_finalize(). Alternatively, if statement
** compilation fails, NULL is returned, *pRc is set to an SQLite error
** code and *pzErr may be set to an error message buffer allocated by
** sqlite3_malloc().
*/
static sqlite3_stmt *unionPrepare(
int *pRc, /* IN/OUT: Error code */
sqlite3 *db, /* Database handle */
const char *zSql, /* SQL statement to prepare */
char **pzErr /* OUT: Error message */
){
sqlite3_stmt *pRet = 0;
if( *pRc==SQLITE_OK ){
int rc = sqlite3_prepare_v2(db, zSql, -1, &pRet, 0);
if( rc!=SQLITE_OK ){
*pzErr = sqlite3_mprintf("sql error: %s", sqlite3_errmsg(db));
*pRc = rc;
}
}
return pRet;
}
/*
** Like unionPrepare(), except prepare the results of vprintf(zFmt, ...)
** instead of a constant SQL string.
*/
static sqlite3_stmt *unionPreparePrintf(
int *pRc, /* IN/OUT: Error code */
char **pzErr, /* OUT: Error message */
sqlite3 *db, /* Database handle */
const char *zFmt, /* printf() format string */
... /* Trailing printf args */
){
sqlite3_stmt *pRet = 0;
char *zSql;
va_list ap;
va_start(ap, zFmt);
zSql = sqlite3_vmprintf(zFmt, ap);
if( *pRc==SQLITE_OK ){
if( zSql==0 ){
*pRc = SQLITE_NOMEM;
}else{
pRet = unionPrepare(pRc, db, zSql, pzErr);
}
}
sqlite3_free(zSql);
va_end(ap);
return pRet;
}
/*
** Call sqlite3_reset() on SQL statement pStmt. If *pRc is set to
** SQLITE_OK when this function is called, then it is set to the
** value returned by sqlite3_reset() before this function exits.
** In this case, *pzErr may be set to point to an error message
** buffer allocated by sqlite3_malloc().
*/
static void unionReset(int *pRc, sqlite3_stmt *pStmt, char **pzErr){
int rc = sqlite3_reset(pStmt);
if( *pRc==SQLITE_OK ){
*pRc = rc;
if( rc ){
*pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(sqlite3_db_handle(pStmt)));
}
}
}
/*
** Call sqlite3_finalize() on SQL statement pStmt. If *pRc is set to
** SQLITE_OK when this function is called, then it is set to the
** value returned by sqlite3_finalize() before this function exits.
*/
static void unionFinalize(int *pRc, sqlite3_stmt *pStmt){
int rc = sqlite3_finalize(pStmt);
if( *pRc==SQLITE_OK ) *pRc = rc;
}
/*
** xDisconnect method.
*/
static int unionDisconnect(sqlite3_vtab *pVtab){
if( pVtab ){
UnionTab *pTab = (UnionTab*)pVtab;
int i;
for(i=0; i<pTab->nSrc; i++){
sqlite3_free(pTab->aSrc[i].zDb);
sqlite3_free(pTab->aSrc[i].zTab);
}
sqlite3_free(pTab->aSrc);
sqlite3_free(pTab);
}
return SQLITE_OK;
}
/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is
** called. In this case it returns NULL.
**
** Otherwise, this function checks that the source table passed as the
** second argument (a) exists, (b) is not a view and (c) has a column
** named "_rowid_" of type "integer" that is the primary key.
** If this is not the case, *pRc is set to SQLITE_ERROR and NULL is
** returned.
**
** Finally, if the source table passes the checks above, a nul-terminated
** string describing the column names and types belonging to the source
** table is returned. Tables with the same set of column names and types
** cause this function to return identical strings. Is is the responsibility
** of the caller to free the returned string using sqlite3_free() when
** it is no longer required.
*/
static char *unionSourceToStr(
int *pRc, /* IN/OUT: Error code */
sqlite3 *db, /* Database handle */
UnionSrc *pSrc, /* Source table to test */
sqlite3_stmt *pStmt,
char **pzErr /* OUT: Error message */
){
char *zRet = 0;
if( *pRc==SQLITE_OK ){
int bPk = 0;
const char *zType = 0;
int rc;
sqlite3_table_column_metadata(
db, pSrc->zDb, pSrc->zTab, "_rowid_", &zType, 0, 0, &bPk, 0
);
rc = sqlite3_errcode(db);
if( rc==SQLITE_ERROR
|| (rc==SQLITE_OK && (!bPk || sqlite3_stricmp("integer", zType)))
){
rc = SQLITE_ERROR;
*pzErr = sqlite3_mprintf("no such rowid table: %s%s%s",
(pSrc->zDb ? pSrc->zDb : ""),
(pSrc->zDb ? "." : ""),
pSrc->zTab
);
}
if( rc==SQLITE_OK ){
sqlite3_bind_text(pStmt, 1, pSrc->zTab, -1, SQLITE_STATIC);
sqlite3_bind_text(pStmt, 2, pSrc->zDb, -1, SQLITE_STATIC);
if( SQLITE_ROW==sqlite3_step(pStmt) ){
zRet = unionStrdup(&rc, (const char*)sqlite3_column_text(pStmt, 0));
}
unionReset(&rc, pStmt, pzErr);
}
*pRc = rc;
}
return zRet;
}
/*
** Check that all configured source tables exist and have the same column
** names and datatypes. If this is not the case, or if some other error
** occurs, return an SQLite error code. In this case *pzErr may be set
** to point to an error message buffer allocated by sqlite3_mprintf().
** Or, if no problems regarding the source tables are detected and no
** other error occurs, SQLITE_OK is returned.
*/
static int unionSourceCheck(UnionTab *pTab, char **pzErr){
const char *zSql =
"SELECT group_concat(quote(name) || '.' || quote(type)) "
"FROM pragma_table_info(?, ?)";
int rc = SQLITE_OK;
if( pTab->nSrc==0 ){
*pzErr = sqlite3_mprintf("no source tables configured");
rc = SQLITE_ERROR;
}else{
sqlite3_stmt *pStmt = 0;
char *z0 = 0;
int i;
pStmt = unionPrepare(&rc, pTab->db, zSql, pzErr);
if( rc==SQLITE_OK ){
z0 = unionSourceToStr(&rc, pTab->db, &pTab->aSrc[0], pStmt, pzErr);
}
for(i=1; i<pTab->nSrc; i++){
char *z = unionSourceToStr(&rc, pTab->db, &pTab->aSrc[i], pStmt, pzErr);
if( rc==SQLITE_OK && sqlite3_stricmp(z, z0) ){
*pzErr = sqlite3_mprintf("source table schema mismatch");
rc = SQLITE_ERROR;
}
sqlite3_free(z);
}
unionFinalize(&rc, pStmt);
sqlite3_free(z0);
}
return rc;
}
/*
** xConnect/xCreate method.
**
** The argv[] array contains the following:
**
** argv[0] -> module name ("unionvtab")
** argv[1] -> database name
** argv[2] -> table name
** argv[3] -> SQL statement
*/
static int unionConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
UnionTab *pTab = 0;
int rc = SQLITE_OK;
(void)pAux; /* Suppress harmless 'unused parameter' warning */
if( sqlite3_stricmp("temp", argv[1]) ){
/* unionvtab tables may only be created in the temp schema */
*pzErr = sqlite3_mprintf("unionvtab tables must be created in TEMP schema");
rc = SQLITE_ERROR;
}else if( argc!=4 ){
*pzErr = sqlite3_mprintf("wrong number of arguments for unionvtab");
rc = SQLITE_ERROR;
}else{
int nAlloc = 0; /* Allocated size of pTab->aSrc[] */
sqlite3_stmt *pStmt = 0; /* Argument statement */
char *zArg = unionStrdup(&rc, argv[3]); /* Copy of argument to CVT */
/* Prepare the SQL statement. Instead of executing it directly, sort
** the results by the "minimum rowid" field. This makes it easier to
** check that there are no rowid range overlaps between source tables
** and that the UnionTab.aSrc[] array is always sorted by rowid. */
unionDequote(zArg);
pStmt = unionPreparePrintf(&rc, pzErr, db,
"SELECT * FROM (%z) ORDER BY 3", zArg
);
/* Allocate the UnionTab structure */
pTab = unionMalloc(&rc, sizeof(UnionTab));
/* Iterate through the rows returned by the SQL statement specified
** as an argument to the CREATE VIRTUAL TABLE statement. */
while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
const char *zDb = (const char*)sqlite3_column_text(pStmt, 0);
const char *zTab = (const char*)sqlite3_column_text(pStmt, 1);
sqlite3_int64 iMin = sqlite3_column_int64(pStmt, 2);
sqlite3_int64 iMax = sqlite3_column_int64(pStmt, 3);
UnionSrc *pSrc;
/* Grow the pTab->aSrc[] array if required. */
if( nAlloc<=pTab->nSrc ){
int nNew = nAlloc ? nAlloc*2 : 8;
UnionSrc *aNew = (UnionSrc*)sqlite3_realloc(
pTab->aSrc, nNew*sizeof(UnionSrc)
);
if( aNew==0 ){
rc = SQLITE_NOMEM;
break;
}else{
memset(&aNew[pTab->nSrc], 0, (nNew-pTab->nSrc)*sizeof(UnionSrc));
pTab->aSrc = aNew;
nAlloc = nNew;
}
}
/* Check for problems with the specified range of rowids */
if( iMax<iMin || (pTab->nSrc>0 && iMin<=pTab->aSrc[pTab->nSrc-1].iMax) ){
*pzErr = sqlite3_mprintf("rowid range mismatch error");
rc = SQLITE_ERROR;
}
pSrc = &pTab->aSrc[pTab->nSrc++];
pSrc->zDb = unionStrdup(&rc, zDb);
pSrc->zTab = unionStrdup(&rc, zTab);
pSrc->iMin = iMin;
pSrc->iMax = iMax;
}
unionFinalize(&rc, pStmt);
pStmt = 0;
/* Verify that all source tables exist and have compatible schemas. */
if( rc==SQLITE_OK ){
pTab->db = db;
rc = unionSourceCheck(pTab, pzErr);
}
/* Compose a CREATE TABLE statement and pass it to declare_vtab() */
if( rc==SQLITE_OK ){
pStmt = unionPreparePrintf(&rc, pzErr, db, "SELECT "
"'CREATE TABLE xyz('"
" || group_concat(quote(name) || ' ' || type, ', ')"
" || ')',"
"max((cid+1) * (type='INTEGER' COLLATE nocase AND pk=1))-1 "
"FROM pragma_table_info(%Q, ?)",
pTab->aSrc[0].zTab, pTab->aSrc[0].zDb
);
}
if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
const char *zDecl = (const char*)sqlite3_column_text(pStmt, 0);
rc = sqlite3_declare_vtab(db, zDecl);
pTab->iPK = sqlite3_column_int(pStmt, 1);
}
unionFinalize(&rc, pStmt);
}
if( rc!=SQLITE_OK ){
unionDisconnect((sqlite3_vtab*)pTab);
pTab = 0;
}
*ppVtab = (sqlite3_vtab*)pTab;
return rc;
}
/*
** xOpen
*/
static int unionOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
UnionCsr *pCsr;
int rc = SQLITE_OK;
(void)p; /* Suppress harmless warning */
pCsr = (UnionCsr*)unionMalloc(&rc, sizeof(UnionCsr));
*ppCursor = &pCsr->base;
return rc;
}
/*
** xClose
*/
static int unionClose(sqlite3_vtab_cursor *cur){
UnionCsr *pCsr = (UnionCsr*)cur;
sqlite3_finalize(pCsr->pStmt);
sqlite3_free(pCsr);
return SQLITE_OK;
}
/*
** xNext
*/
static int unionNext(sqlite3_vtab_cursor *cur){
UnionCsr *pCsr = (UnionCsr*)cur;
int rc;
assert( pCsr->pStmt );
if( sqlite3_step(pCsr->pStmt)!=SQLITE_ROW ){
rc = sqlite3_finalize(pCsr->pStmt);
pCsr->pStmt = 0;
}else{
rc = SQLITE_OK;
}
return rc;
}
/*
** xColumn
*/
static int unionColumn(
sqlite3_vtab_cursor *cur,
sqlite3_context *ctx,
int i
){
UnionCsr *pCsr = (UnionCsr*)cur;
sqlite3_result_value(ctx, sqlite3_column_value(pCsr->pStmt, i+1));
return SQLITE_OK;
}
/*
** xRowid
*/
static int unionRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
UnionCsr *pCsr = (UnionCsr*)cur;
*pRowid = sqlite3_column_int64(pCsr->pStmt, 0);
return SQLITE_OK;
}
/*
** xEof
*/
static int unionEof(sqlite3_vtab_cursor *cur){
UnionCsr *pCsr = (UnionCsr*)cur;
return pCsr->pStmt==0;
}
/*
** xFilter
*/
static int unionFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
UnionTab *pTab = (UnionTab*)(pVtabCursor->pVtab);
UnionCsr *pCsr = (UnionCsr*)pVtabCursor;
int rc = SQLITE_OK;
int i;
char *zSql = 0;
int bZero = 0;
sqlite3_int64 iMin = SMALLEST_INT64;
sqlite3_int64 iMax = LARGEST_INT64;
assert( idxNum==0
|| idxNum==SQLITE_INDEX_CONSTRAINT_EQ
|| idxNum==SQLITE_INDEX_CONSTRAINT_LE
|| idxNum==SQLITE_INDEX_CONSTRAINT_GE
|| idxNum==SQLITE_INDEX_CONSTRAINT_LT
|| idxNum==SQLITE_INDEX_CONSTRAINT_GT
|| idxNum==(SQLITE_INDEX_CONSTRAINT_GE|SQLITE_INDEX_CONSTRAINT_LE)
);
(void)idxStr; /* Suppress harmless warning */
if( idxNum==SQLITE_INDEX_CONSTRAINT_EQ ){
assert( argc==1 );
iMin = iMax = sqlite3_value_int64(argv[0]);
}else{
if( idxNum & (SQLITE_INDEX_CONSTRAINT_LE|SQLITE_INDEX_CONSTRAINT_LT) ){
assert( argc>=1 );
iMax = sqlite3_value_int64(argv[0]);
if( idxNum & SQLITE_INDEX_CONSTRAINT_LT ){
if( iMax==SMALLEST_INT64 ){
bZero = 1;
}else{
iMax--;
}
}
}
if( idxNum & (SQLITE_INDEX_CONSTRAINT_GE|SQLITE_INDEX_CONSTRAINT_GT) ){
assert( argc>=1 );
iMin = sqlite3_value_int64(argv[argc-1]);
if( idxNum & SQLITE_INDEX_CONSTRAINT_GT ){
if( iMin==LARGEST_INT64 ){
bZero = 1;
}else{
iMin++;
}
}
}
}
sqlite3_finalize(pCsr->pStmt);
pCsr->pStmt = 0;
if( bZero ){
return SQLITE_OK;
}
for(i=0; i<pTab->nSrc; i++){
UnionSrc *pSrc = &pTab->aSrc[i];
if( iMin>pSrc->iMax || iMax<pSrc->iMin ){
continue;
}
zSql = sqlite3_mprintf("%z%sSELECT rowid, * FROM %s%q%s%Q"
, zSql
, (zSql ? " UNION ALL " : "")
, (pSrc->zDb ? "'" : "")
, (pSrc->zDb ? pSrc->zDb : "")
, (pSrc->zDb ? "'." : "")
, pSrc->zTab
);
if( zSql==0 ){
rc = SQLITE_NOMEM;
break;
}
if( iMin==iMax ){
zSql = sqlite3_mprintf("%z WHERE rowid=%lld", zSql, iMin);
}else{
const char *zWhere = "WHERE";
if( iMin!=SMALLEST_INT64 && iMin>pSrc->iMin ){
zSql = sqlite3_mprintf("%z WHERE rowid>=%lld", zSql, iMin);
zWhere = "AND";
}
if( iMax!=LARGEST_INT64 && iMax<pSrc->iMax ){
zSql = sqlite3_mprintf("%z %s rowid<=%lld", zSql, zWhere, iMax);
}
}
}
if( zSql==0 ) return rc;
pCsr->pStmt = unionPrepare(&rc, pTab->db, zSql, &pTab->base.zErrMsg);
sqlite3_free(zSql);
if( rc!=SQLITE_OK ) return rc;
return unionNext(pVtabCursor);
}
/*
** xBestIndex.
**
** This implementation searches for constraints on the rowid field. EQ,
** LE, LT, GE and GT are handled.
**
** If there is an EQ comparison, then idxNum is set to INDEX_CONSTRAINT_EQ.
** In this case the only argument passed to xFilter is the rhs of the ==
** operator.
**
** Otherwise, if an LE or LT constraint is found, then the INDEX_CONSTRAINT_LE
** or INDEX_CONSTRAINT_LT (but not both) bit is set in idxNum. The first
** argument to xFilter is the rhs of the <= or < operator. Similarly, if
** an GE or GT constraint is found, then the INDEX_CONSTRAINT_GE or
** INDEX_CONSTRAINT_GT bit is set in idxNum. The rhs of the >= or > operator
** is passed as either the first or second argument to xFilter, depending
** on whether or not there is also a LT|LE constraint.
*/
static int unionBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
UnionTab *pTab = (UnionTab*)tab;
int iEq = -1;
int iLt = -1;
int iGt = -1;
int i;
for(i=0; i<pIdxInfo->nConstraint; i++){
struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i];
if( p->usable && (p->iColumn<0 || p->iColumn==pTab->iPK) ){
switch( p->op ){
case SQLITE_INDEX_CONSTRAINT_EQ:
iEq = i;
break;
case SQLITE_INDEX_CONSTRAINT_LE:
case SQLITE_INDEX_CONSTRAINT_LT:
iLt = i;
break;
case SQLITE_INDEX_CONSTRAINT_GE:
case SQLITE_INDEX_CONSTRAINT_GT:
iGt = i;
break;
}
}
}
if( iEq>=0 ){
pIdxInfo->estimatedRows = 1;
pIdxInfo->idxFlags = SQLITE_INDEX_SCAN_UNIQUE;
pIdxInfo->estimatedCost = 3.0;
pIdxInfo->idxNum = SQLITE_INDEX_CONSTRAINT_EQ;
pIdxInfo->aConstraintUsage[iEq].argvIndex = 1;
pIdxInfo->aConstraintUsage[iEq].omit = 1;
}else{
int iCons = 1;
int idxNum = 0;
sqlite3_int64 nRow = 1000000;
if( iLt>=0 ){
nRow = nRow / 2;
pIdxInfo->aConstraintUsage[iLt].argvIndex = iCons++;
pIdxInfo->aConstraintUsage[iLt].omit = 1;
idxNum |= pIdxInfo->aConstraint[iLt].op;
}
if( iGt>=0 ){
nRow = nRow / 2;
pIdxInfo->aConstraintUsage[iGt].argvIndex = iCons++;
pIdxInfo->aConstraintUsage[iGt].omit = 1;
idxNum |= pIdxInfo->aConstraint[iGt].op;
}
pIdxInfo->estimatedRows = nRow;
pIdxInfo->estimatedCost = 3.0 * (double)nRow;
pIdxInfo->idxNum = idxNum;
}
return SQLITE_OK;
}
/*
** Register the unionvtab virtual table module with database handle db.
*/
static int createUnionVtab(sqlite3 *db){
static sqlite3_module unionModule = {
0, /* iVersion */
unionConnect,
unionConnect,
unionBestIndex, /* xBestIndex - query planner */
unionDisconnect,
unionDisconnect,
unionOpen, /* xOpen - open a cursor */
unionClose, /* xClose - close a cursor */
unionFilter, /* xFilter - configure scan constraints */
unionNext, /* xNext - advance a cursor */
unionEof, /* xEof - check for end of scan */
unionColumn, /* xColumn - read data */
unionRowid, /* xRowid - read data */
0, /* xUpdate */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
0, /* xSavepoint */
0, /* xRelease */
0 /* xRollbackTo */
};
return sqlite3_create_module(db, "unionvtab", &unionModule, 0);
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_unionvtab_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
(void)pzErrMsg; /* Suppress harmless warning */
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = createUnionVtab(db);
#endif
return rc;
}