/*
** 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.
**
*************************************************************************
**
*/
#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_UNIONVTAB)
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
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 cursor type for union vtab.
*/
struct UnionCsr {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3_stmt *pStmt; /* SQL statement to run */
};
/*
** Virtual table type for union vtab.
*/
struct UnionTab {
sqlite3_vtab base; /* Base class - must be first */
sqlite3 *db; /* Database handle */
int nSrc; /* Number of elements in the aSrc[] array */
UnionSrc *aSrc; /* Array of source tables, sorted by rowid */
};
/*
** 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 = 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){
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';
}
}
static sqlite3_stmt *unionPrepare(
int *pRc,
sqlite3 *db,
const char *zSql,
char **pzErr
){
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;
}
static void unionReset(int *pRc, sqlite3_stmt *pStmt, char **pzErr){
int rc = sqlite3_reset(pStmt);
if( *pRc==SQLITE_OK ){
*pRc = rc;
if( rc && pzErr ){
*pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(sqlite3_db_handle(pStmt)));
}
}
}
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;
}
static char *unionSourceToStr(
int *pRc,
UnionSrc *pSrc,
sqlite3_stmt *pStmt,
char **pzErr
){
char *zRet = 0;
if( *pRc==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(pRc, (const char*)sqlite3_column_text(pStmt, 0));
}
unionReset(pRc, pStmt, pzErr);
if( *pRc==SQLITE_OK && zRet==0 ){
*pRc = SQLITE_ERROR;
*pzErr = sqlite3_mprintf("no such table: %s%s%s",
(pSrc->zDb ? pSrc->zDb : ""),
(pSrc->zDb ? "." : ""),
pSrc->zTab
);
}
}
return zRet;
}
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->aSrc[0], pStmt, pzErr);
}
for(i=1; i<pTab->nSrc; i++){
char *z = unionSourceToStr(&rc, &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;
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 *zSql1 = unionStrdup(&rc, argv[3]);
char *zSql2 = 0;
if( zSql1 ){
unionDequote(zSql1);
zSql2 = sqlite3_mprintf("SELECT * FROM (%s) ORDER BY 3", zSql1);
sqlite3_free(zSql1);
zSql1 = 0;
}
if( zSql2==0 ){
rc = SQLITE_NOMEM;
}
pTab = unionMalloc(&rc, sizeof(UnionTab));
pStmt = unionPrepare(&rc, db, zSql2, pzErr);
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;
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;
}
}
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;
sqlite3_free(zSql1);
sqlite3_free(zSql2);
zSql1 = 0;
zSql2 = 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 ){
zSql1 = sqlite3_mprintf("SELECT "
"'CREATE TABLE xyz('"
" || group_concat(quote(name) || ' ' || type, ', ')"
" || ')'"
"FROM pragma_table_info(%Q, ?)",
pTab->aSrc[0].zTab
);
if( zSql1==0 ) rc = SQLITE_NOMEM;
}
pStmt = unionPrepare(&rc, db, zSql1, pzErr);
if( rc==SQLITE_OK ){
sqlite3_bind_text(pStmt, 1, pTab->aSrc[0].zDb, -1, SQLITE_STATIC);
if( SQLITE_ROW==sqlite3_step(pStmt) ){
const char *zDecl = (const char*)sqlite3_column_text(pStmt, 0);
rc = sqlite3_declare_vtab(db, zDecl);
}
}
unionFinalize(&rc, pStmt);
sqlite3_free(zSql1);
}
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;
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 bMinValid = 0;
int bMaxValid = 0;
sqlite3_int64 iMin;
sqlite3_int64 iMax;
if( idxNum==SQLITE_INDEX_CONSTRAINT_EQ ){
assert( argc==1 );
iMin = iMax = sqlite3_value_int64(argv[0]);
bMinValid = bMaxValid = 1;
}else{
if( idxNum & SQLITE_INDEX_CONSTRAINT_LE ){
assert( argc>=1 );
iMax = sqlite3_value_int64(argv[0]);
bMaxValid = 1;
}
if( idxNum & SQLITE_INDEX_CONSTRAINT_GE ){
assert( argc>=1 );
iMin = sqlite3_value_int64(argv[argc-1]);
bMinValid = 1;
}
}
sqlite3_finalize(pCsr->pStmt);
pCsr->pStmt = 0;
for(i=0; i<pTab->nSrc; i++){
UnionSrc *pSrc = &pTab->aSrc[i];
if( (bMinValid && iMin>pSrc->iMax) || (bMaxValid && 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( zSql ){
if( bMinValid && bMaxValid && iMin==iMax ){
zSql = sqlite3_mprintf("%z WHERE rowid=%lld", zSql, iMin);
}else{
const char *zWhere = "WHERE";
if( bMinValid && iMin>pSrc->iMin ){
zSql = sqlite3_mprintf("%z WHERE rowid>=%lld", zSql, iMin);
zWhere = "AND";
}
if( bMaxValid && iMax<pSrc->iMax ){
zSql = sqlite3_mprintf("%z %s rowid<=%lld", zSql, zWhere, iMax);
}
}
}
}
if( rc==SQLITE_OK ){
pCsr->pStmt = unionPrepare(&rc, pTab->db, zSql, &pTab->base.zErrMsg);
}
sqlite3_free(zSql);
if( rc!=SQLITE_OK ) return rc;
return unionNext(pVtabCursor);
}
/*
** xBestIndex.
*/
static int unionBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
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 ){
switch( p->op ){
case SQLITE_INDEX_CONSTRAINT_EQ:
if( iEq<0 ) iEq = i;
break;
case SQLITE_INDEX_CONSTRAINT_LE:
case SQLITE_INDEX_CONSTRAINT_LT:
if( iLt<0 ) iLt = i;
break;
case SQLITE_INDEX_CONSTRAINT_GE:
case SQLITE_INDEX_CONSTRAINT_GT:
if( iGt<0 ) 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;
}else{
int iCons = 1;
int idxNum = 0;
sqlite3_int64 nRow = 1000000;
if( iLt>=0 ){
nRow = nRow / 2;
pIdxInfo->aConstraintUsage[iLt].argvIndex = iCons++;
idxNum |= SQLITE_INDEX_CONSTRAINT_LE;
}
if( iGt>=0 ){
nRow = nRow / 2;
pIdxInfo->aConstraintUsage[iGt].argvIndex = iCons++;
idxNum |= SQLITE_INDEX_CONSTRAINT_GE;
}
pIdxInfo->estimatedRows = nRow;
pIdxInfo->estimatedCost = 3.0 * (double)nRow;
pIdxInfo->idxNum = idxNum;
}
return SQLITE_OK;
}
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 */
};
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);
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = createUnionVtab(db);
#endif
return rc;
}
#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_UNIONVTAB) */