@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $ Header : / cvsroot / pgsql / src / backend / commands / portalcmds . c , v 1.8 2003 / 01 / 08 00 : 22 : 27 tgl Exp $
* $ Header : / cvsroot / pgsql / src / backend / commands / portalcmds . c , v 1.9 2003 / 03 / 10 03 : 53 : 49 tgl Exp $
*
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
*/
@ -19,39 +19,88 @@
# include "commands/portalcmds.h"
# include "executor/executor.h"
# include "optimizer/planner.h"
# include "rewrite/rewriteHandler.h"
static Portal PreparePortal ( char * portalName ) ;
/*
* PortalCleanup
*
* Clean up a portal when it ' s dropped . Since this mainly exists to run
* ExecutorEnd ( ) , it should not be set as the cleanup hook until we have
* called ExecutorStart ( ) on the portal ' s query .
* PerformCursorOpen
* Execute SQL DECLARE CURSOR command .
*/
void
PortalCleanup ( Portal portal )
PerformCursorOpen ( DeclareCursorStmt * stmt , CommandDest dest )
{
List * rewritten ;
Query * query ;
Plan * plan ;
Portal portal ;
MemoryContext oldContext ;
char * cursorName ;
QueryDesc * queryDesc ;
/* Check for invalid context (must be in transaction block) */
RequireTransactionChain ( ( void * ) stmt , " DECLARE CURSOR " ) ;
/*
* sanity checks
* The query has been through parse analysis , but not rewriting or
* planning as yet . Note that the grammar ensured we have a SELECT
* query , so we are not expecting rule rewriting to do anything strange .
*/
AssertArg ( PortalIsValid ( portal ) ) ;
AssertArg ( portal - > cleanup = = PortalCleanup ) ;
rewritten = QueryRewrite ( ( Query * ) stmt - > query ) ;
if ( length ( rewritten ) ! = 1 | | ! IsA ( lfirst ( rewritten ) , Query ) )
elog ( ERROR , " PerformCursorOpen: unexpected rewrite result " ) ;
query = ( Query * ) lfirst ( rewritten ) ;
if ( query - > commandType ! = CMD_SELECT )
elog ( ERROR , " PerformCursorOpen: unexpected rewrite result " ) ;
if ( query - > into )
elog ( ERROR , " DECLARE CURSOR may not specify INTO " ) ;
if ( query - > rowMarks ! = NIL )
elog ( ERROR , " DECLARE/UPDATE is not supported "
" \n \t Cursors must be READ ONLY " ) ;
plan = planner ( query , true , stmt - > options ) ;
/* If binary cursor, switch to alternate output format */
if ( ( stmt - > options & CURSOR_OPT_BINARY ) & & dest = = Remote )
dest = RemoteInternal ;
/*
* tell the executor to shutdown the query
* Crea te a portal and copy the query and plan into its memory context .
*/
ExecutorEnd ( PortalGetQueryDesc ( portal ) ) ;
portal = PreparePortal ( stmt - > portalname ) ;
oldContext = MemoryContextSwitchTo ( PortalGetHeapMemory ( portal ) ) ;
query = copyObject ( query ) ;
plan = copyObject ( plan ) ;
/*
* This should be unnecessary since the querydesc should be in the
* portal ' s memory context , but do it anyway for symmetry .
* Create the QueryDesc object in the portal context , too .
*/
FreeQueryDesc ( PortalGetQueryDesc ( portal ) ) ;
}
cursorName = pstrdup ( stmt - > portalname ) ;
queryDesc = CreateQueryDesc ( query , plan , dest , cursorName , NULL , false ) ;
/*
* call ExecStart to prepare the plan for execution
*/
ExecutorStart ( queryDesc ) ;
/* Arrange to shut down the executor if portal is dropped */
PortalSetQuery ( portal , queryDesc , PortalCleanup ) ;
/*
* We ' re done ; the query won ' t actually be run until PerformPortalFetch
* is called .
*/
MemoryContextSwitchTo ( oldContext ) ;
}
/*
* PerformPortalFetch
* Execute SQL FETCH or MOVE command .
*
* name : name of portal
* forward : forward or backward fetch ?
@ -70,28 +119,20 @@ PerformPortalFetch(char *name,
char * completionTag )
{
Portal portal ;
QueryDesc * queryDesc ;
EState * estate ;
MemoryContext oldcontext ;
ScanDirection direction ;
bool temp_desc = false ;
long nprocessed ;
/* initialize completion status in case of early exit */
if ( completionTag )
strcpy ( completionTag , ( dest = = None ) ? " MOVE 0 " : " FETCH 0 " ) ;
/*
* sanity checks
*/
/* sanity checks */
if ( name = = NULL )
{
elog ( WARNING , " PerformPortalFetch: missing portal name " ) ;
return ;
}
/*
* get the portal from the portal name
*/
/* get the portal from the portal name */
portal = GetPortalByName ( name ) ;
if ( ! PortalIsValid ( portal ) )
{
@ -100,6 +141,31 @@ PerformPortalFetch(char *name,
return ;
}
/* Do it */
nprocessed = DoPortalFetch ( portal , forward , count , dest ) ;
/* Return command status if wanted */
if ( completionTag )
snprintf ( completionTag , COMPLETION_TAG_BUFSIZE , " %s %ld " ,
( dest = = None ) ? " MOVE " : " FETCH " ,
nprocessed ) ;
}
/*
* DoPortalFetch
* Guts of PerformPortalFetch - - - shared with SPI cursor operations
*
* Returns number of rows processed .
*/
long
DoPortalFetch ( Portal portal , bool forward , long count , CommandDest dest )
{
QueryDesc * queryDesc ;
EState * estate ;
MemoryContext oldcontext ;
ScanDirection direction ;
bool temp_desc = false ;
/*
* Zero count means to re - fetch the current row , if any ( per SQL92 )
*/
@ -113,9 +179,7 @@ PerformPortalFetch(char *name,
if ( dest = = None )
{
/* MOVE 0 returns 0/1 based on if FETCH 0 would return a row */
if ( completionTag & & on_row )
strcpy ( completionTag , " MOVE 1 " ) ;
return ;
return on_row ? 1L : 0L ;
}
else
{
@ -128,9 +192,9 @@ PerformPortalFetch(char *name,
*/
if ( on_row )
{
PerformPortalFetch ( name , false /* backward */ , 1L ,
None , /* throw away output */
NULL /* do not modify the command tag */ ) ;
DoPortalFetch ( portal ,
false /* backward */ , 1L ,
None /* throw away output */ ) ;
/* Set up to fetch one row forward */
count = 1 ;
forward = true ;
@ -202,6 +266,10 @@ PerformPortalFetch(char *name,
}
else
{
if ( ! portal - > backwardOK )
elog ( ERROR , " Cursor cannot scan backwards "
" \n \t Declare it with SCROLL option to enable backward scan " ) ;
if ( portal - > atStart | | count = = 0 )
direction = NoMovementScanDirection ;
else
@ -222,12 +290,6 @@ PerformPortalFetch(char *name,
}
}
/* Return command status if wanted */
if ( completionTag )
snprintf ( completionTag , COMPLETION_TAG_BUFSIZE , " %s %u " ,
( dest = = None ) ? " MOVE " : " FETCH " ,
estate - > es_processed ) ;
/*
* Clean up and switch back to old context .
*/
@ -235,18 +297,21 @@ PerformPortalFetch(char *name,
pfree ( queryDesc ) ;
MemoryContextSwitchTo ( oldcontext ) ;
return estate - > es_processed ;
}
/*
* PerformPortalClose
* Close a cursor .
*/
void
PerformPortalClose ( char * name , CommandDest dest )
PerformPortalClose ( char * name )
{
Portal portal ;
/*
* sanity checks
* sanity checks . . . why is this case allowed by the grammar , anyway ?
*/
if ( name = = NULL )
{
@ -270,3 +335,64 @@ PerformPortalClose(char *name, CommandDest dest)
*/
PortalDrop ( portal ) ;
}
/*
* PreparePortal
*/
static Portal
PreparePortal ( char * portalName )
{
Portal portal ;
/*
* Check for already - in - use portal name .
*/
portal = GetPortalByName ( portalName ) ;
if ( PortalIsValid ( portal ) )
{
/*
* XXX Should we raise an error rather than closing the old
* portal ?
*/
elog ( WARNING , " Closing pre-existing portal \" %s \" " ,
portalName ) ;
PortalDrop ( portal ) ;
}
/*
* Create the new portal .
*/
portal = CreatePortal ( portalName ) ;
return portal ;
}
/*
* PortalCleanup
*
* Clean up a portal when it ' s dropped . Since this mainly exists to run
* ExecutorEnd ( ) , it should not be set as the cleanup hook until we have
* called ExecutorStart ( ) on the portal ' s query .
*/
void
PortalCleanup ( Portal portal )
{
/*
* sanity checks
*/
AssertArg ( PortalIsValid ( portal ) ) ;
AssertArg ( portal - > cleanup = = PortalCleanup ) ;
/*
* tell the executor to shutdown the query
*/
ExecutorEnd ( PortalGetQueryDesc ( portal ) ) ;
/*
* This should be unnecessary since the querydesc should be in the
* portal ' s memory context , but do it anyway for symmetry .
*/
FreeQueryDesc ( PortalGetQueryDesc ( portal ) ) ;
}
Tom Lane
23 years ago