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Add a new system view, pg_cursors, that displays the currently available

Browse Source 
cursors. Patch from Joachim Wieland, review and ediorialization by Neil
Conway. The view lists cursors defined by DECLARE CURSOR, using SPI, or
via the Bind message of the frontend/backend protocol. This means the
view does not list the unnamed portal or the portal created to implement
EXECUTE. Because we do list SPI portals, there might be more rows in
this view than you might expect if you are using SPI implicitly (e.g.
via a procedural language).

Per recent discussion on -hackers, the query string included in the
view for cursors defined by DECLARE CURSOR is based on
debug_query_string. That means it is not accurate if multiple queries
separated by semicolons are submitted as one query string. However,
there doesn't seem a trivial fix for that: debug_query_string
is better than nothing. I also changed SPI_cursor_open() to include
the source text for the portal it creates: AFAICS there is no reason
not to do this.

Update the documentation and regression tests, bump the catversion.
This commit is contained in:
Neil Conway
2006-01-18 06:49:30 +00:00
parent 558bc2584d
commit 33e06ebccb
17 changed files with 388 additions and 32 deletions
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123
src/backend/utils/mmgr/portalmem.c
View File

@ -12,15 +12,19 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.83 2005/11/22 18:17:27 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.84 2006/01/18 06:49:27 neilc Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "miscadmin.h"
#include "access/heapam.h"
#include "catalog/pg_type.h"
#include "commands/portalcmds.h"
#include "executor/executor.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
#include "utils/portal.h"
@ -56,8 +60,8 @@ do { \
\
MemSet(key, 0, MAX_PORTALNAME_LEN); \
StrNCpy(key, NAME, MAX_PORTALNAME_LEN); \
hentry = (PortalHashEnt*)hash_search(PortalHashTable, \
key, HASH_FIND, NULL); \
hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
key, HASH_FIND, NULL); \
if (hentry) \
PORTAL = hentry->portal; \
else \
@ -70,8 +74,8 @@ do { \
\
MemSet(key, 0, MAX_PORTALNAME_LEN); \
StrNCpy(key, NAME, MAX_PORTALNAME_LEN); \
hentry = (PortalHashEnt*)hash_search(PortalHashTable, \
key, HASH_ENTER, &found); \
hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
key, HASH_ENTER, &found); \
if (found) \
elog(ERROR, "duplicate portal name"); \
hentry->portal = PORTAL; \
@ -85,8 +89,8 @@ do { \
\
MemSet(key, 0, MAX_PORTALNAME_LEN); \
StrNCpy(key, PORTAL->name, MAX_PORTALNAME_LEN); \
hentry = (PortalHashEnt*)hash_search(PortalHashTable, \
key, HASH_REMOVE, NULL); \
hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
key, HASH_REMOVE, NULL); \
if (hentry == NULL) \
elog(WARNING, "trying to delete portal name that does not exist"); \
} while(0)
@ -190,12 +194,15 @@ CreatePortal(const char *name, bool allowDup, bool dupSilent)
"Portal");
/* initialize portal fields that don't start off zero */
portal->status = PORTAL_NEW;
portal->cleanup = PortalCleanup;
portal->createSubid = GetCurrentSubTransactionId();
portal->strategy = PORTAL_MULTI_QUERY;
portal->cursorOptions = CURSOR_OPT_NO_SCROLL;
portal->atStart = true;
portal->atEnd = true; /* disallow fetches until query is set */
portal->visible = true;
portal->creation_time = GetCurrentTimestamp();
/* put portal in table (sets portal->name) */
PortalHashTableInsert(portal, name);
@ -756,3 +763,103 @@ AtSubCleanup_Portals(SubTransactionId mySubid)
PortalDrop(portal, false);
}
}
/* Find all available cursors */
Datum
pg_cursor(PG_FUNCTION_ARGS)
{
FuncCallContext *funcctx;
HASH_SEQ_STATUS *hash_seq;
PortalHashEnt *hentry;
/* stuff done only on the first call of the function */
if (SRF_IS_FIRSTCALL())
{
MemoryContext oldcontext;
TupleDesc tupdesc;
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
/*
* switch to memory context appropriate for multiple function
* calls
*/
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
if (PortalHashTable)
{
hash_seq = (HASH_SEQ_STATUS *) palloc(sizeof(HASH_SEQ_STATUS));
hash_seq_init(hash_seq, PortalHashTable);
funcctx->user_fctx = (void *) hash_seq;
}
else
funcctx->user_fctx = NULL;
/*
* build tupdesc for result tuples. This must match the
* definition of the pg_cursors view in system_views.sql
*/
tupdesc = CreateTemplateTupleDesc(6, false);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "statement",
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_holdable",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_binary",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 5, "is_scrollable",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 6, "creation_time",
TIMESTAMPTZOID, -1, 0);
funcctx->tuple_desc = BlessTupleDesc(tupdesc);
MemoryContextSwitchTo(oldcontext);
}
/* stuff done on every call of the function */
funcctx = SRF_PERCALL_SETUP();
hash_seq = (HASH_SEQ_STATUS *) funcctx->user_fctx;
/* if the hash table is uninitialized, we're done */
if (hash_seq == NULL)
SRF_RETURN_DONE(funcctx);
/* loop until we find a visible portal or hit the end of the list */
while ((hentry = hash_seq_search(hash_seq)) != NULL)
{
if (hentry->portal->visible)
break;
}
if (hentry)
{
Portal portal;
Datum result;
HeapTuple tuple;
Datum values[6];
bool nulls[6];
portal = hentry->portal;
MemSet(nulls, 0, sizeof(nulls));
values[0] = DirectFunctionCall1(textin, CStringGetDatum(portal->name));
if (!portal->sourceText)
nulls[1] = true;
else
values[1] = DirectFunctionCall1(textin,
CStringGetDatum(portal->sourceText));
values[2] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_HOLD);
values[3] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_BINARY);
values[4] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_SCROLL);
values[5] = TimestampTzGetDatum(portal->creation_time);
tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
result = HeapTupleGetDatum(tuple);
SRF_RETURN_NEXT(funcctx, result);
}
SRF_RETURN_DONE(funcctx);
}