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Add the optional non-found-callback to the swarm-vtab.

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FossilOrigin-Name: a94e2f600bc766fb459418e674b842628ba21e27cf9942c00cd533507d7b35fe
This commit is contained in:
drh
2017-08-04 20:15:08 +00:00
parent d83e082524
commit a5aed4b10b
4 changed files with 132 additions and 18 deletions
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59
ext/misc/unionvtab.c
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@ -36,7 +36,7 @@
**
** A "unionvtab" virtual table is created as follows:
**
** CREATE VIRTUAL TABLE <name> USING unionvtab(<sql statement>);
** 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
@ -58,12 +58,15 @@
**
** A "swarmvtab" virtual table is created similarly to a unionvtab table:
**
** CREATE VIRTUAL TABLE <name> USING swarmvtab(<sql statement>);
** CREATE VIRTUAL TABLE <name>
** USING swarmvtab(<sql-statement>, <callback>);
**
** The difference is that for a swarmvtab table, the first column returned
** by the <sql statement> must return a path or URI that can be used to open
** the database file containing the source table.
**
** the database file containing the source table. The <callback> option
** is optional. If included, it is the name of an application-defined
** SQL function that is invoked with the URI of the file, if the file
** does not already exist on disk.
*/
#include "sqlite3ext.h"
@ -143,6 +146,7 @@ struct UnionTab {
/* Used by swarmvtab only */
char *zSourceStr; /* Expected unionSourceToStr() value */
char *zNotFoundCallback; /* UDF to invoke if file not found on open */
UnionSrc *pClosable; /* First in list of closable sources */
int nOpen; /* Current number of open sources */
int nMaxOpen; /* Maximum number of open sources */
@ -379,6 +383,7 @@ static int unionDisconnect(sqlite3_vtab *pVtab){
sqlite3_close(pSrc->db);
}
sqlite3_free(pTab->zSourceStr);
sqlite3_free(pTab->zNotFoundCallback);
sqlite3_free(pTab->aSrc);
sqlite3_free(pTab);
}
@ -491,6 +496,35 @@ static int unionSourceCheck(UnionTab *pTab, char **pzErr){
return rc;
}
/*
** Try to open the swarmvtab database. If initially unable, invoke the
** not-found callback UDF and then try again.
*/
static int unionOpenDatabaseInner(UnionTab *pTab, UnionSrc *pSrc, char **pzErr){
int rc = SQLITE_OK;
static const int openFlags =
SQLITE_OPEN_READONLY | SQLITE_OPEN_URI;
rc = sqlite3_open_v2(pSrc->zFile, &pSrc->db, openFlags, 0);
if( rc==SQLITE_OK ) return rc;
if( pTab->zNotFoundCallback ){
char *zSql = sqlite3_mprintf("SELECT \"%w\"(%Q);",
pTab->zNotFoundCallback, pSrc->zFile);
if( zSql==0 ){
*pzErr = sqlite3_mprintf("out of memory");
return SQLITE_NOMEM;
}
rc = sqlite3_exec(pTab->db, zSql, 0, 0, pzErr);
sqlite3_free(zSql);
if( rc ) return rc;
rc = sqlite3_open_v2(pSrc->zFile, &pSrc->db, openFlags, 0);
}
if( rc!=SQLITE_OK ){
*pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(pSrc->db));
}
return rc;
}
/*
** This function may only be called for swarmvtab tables. The results of
** calling it on a unionvtab table are undefined.
@ -513,10 +547,8 @@ static int unionOpenDatabase(UnionTab *pTab, int iSrc, char **pzErr){
assert( pTab->bSwarm && iSrc<pTab->nSrc );
if( pSrc->db==0 ){
unionCloseSources(pTab, pTab->nMaxOpen-1);
rc = sqlite3_open_v2(pSrc->zFile, &pSrc->db, SQLITE_OPEN_READONLY, 0);
if( rc!=SQLITE_OK ){
*pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(pSrc->db));
}else{
rc = unionOpenDatabaseInner(pTab, pSrc, pzErr);
if( rc==SQLITE_OK ){
char *z = unionSourceToStr(&rc, pTab, pSrc, pzErr);
if( rc==SQLITE_OK ){
if( pTab->zSourceStr==0 ){
@ -598,10 +630,11 @@ static int unionFinalizeCsrStmt(UnionCsr *pCsr){
**
** The argv[] array contains the following:
**
** argv[0] -> module name ("unionvtab")
** argv[0] -> module name ("unionvtab" or "swarmvtab")
** argv[1] -> database name
** argv[2] -> table name
** argv[3] -> SQL statement
** argv[4] -> not-found callback UDF name
*/
static int unionConnect(
sqlite3 *db,
@ -619,7 +652,7 @@ static int unionConnect(
/* unionvtab tables may only be created in the temp schema */
*pzErr = sqlite3_mprintf("%s tables must be created in TEMP schema", zVtab);
rc = SQLITE_ERROR;
}else if( argc!=4 ){
}else if( argc!=4 && argc!=5 ){
*pzErr = sqlite3_mprintf("wrong number of arguments for %s", zVtab);
rc = SQLITE_ERROR;
}else{
@ -685,6 +718,12 @@ static int unionConnect(
unionFinalize(&rc, pStmt, pzErr);
pStmt = 0;
/* Capture the not-found callback UDF name */
if( argc>=5 ){
pTab->zNotFoundCallback = unionStrdup(&rc, argv[4]);
unionDequote(pTab->zNotFoundCallback);
}
/* It is an error if the SELECT statement returned zero rows. If only
** because there is no way to determine the schema of the virtual
** table in this case. */