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Improve UPDATE/DELETE WHERE CURRENT OF so that they can be used from plpgsql

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with a plpgsql-defined cursor.  The underlying mechanism for this is that the
main SQL engine will now take "WHERE CURRENT OF $n" where $n is a refcursor
parameter.  Not sure if we should document that fact or consider it an
implementation detail.  Per discussion with Pavel Stehule.
This commit is contained in:
Tom Lane
2007-06-11 22:22:42 +00:00
parent bdc71c2cb1
commit a9545b3aef
13 changed files with 225 additions and 72 deletions
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74
src/backend/executor/execCurrent.c
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@ -6,26 +6,29 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/executor/execCurrent.c,v 1.1 2007/06/11 01:16:22 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/execCurrent.c,v 1.2 2007/06/11 22:22:40 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "catalog/pg_type.h"
#include "executor/executor.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/portal.h"
static char *fetch_param_value(ExprContext *econtext, int paramId);
static ScanState *search_plan_tree(PlanState *node, Oid table_oid);
/*
* execCurrentOf
*
* Given the name of a cursor and the OID of a table, determine which row
* of the table is currently being scanned by the cursor, and return its
* TID into *current_tid.
* Given a CURRENT OF expression and the OID of a table, determine which row
* of the table is currently being scanned by the cursor named by CURRENT OF,
* and return the row's TID into *current_tid.
*
* Returns TRUE if a row was identified. Returns FALSE if the cursor is valid
* for the table but is not currently scanning a row of the table (this is a
@ -33,14 +36,25 @@ static ScanState *search_plan_tree(PlanState *node, Oid table_oid);
* valid updatable scan of the specified table.
*/
bool
execCurrentOf(char *cursor_name, Oid table_oid,
execCurrentOf(CurrentOfExpr *cexpr,
ExprContext *econtext,
Oid table_oid,
ItemPointer current_tid)
{
char *cursor_name;
char *table_name;
Portal portal;
QueryDesc *queryDesc;
ScanState *scanstate;
HeapTuple tup;
bool lisnull;
Oid tuple_tableoid;
ItemPointer tuple_tid;
/* Get the cursor name --- may have to look up a parameter reference */
if (cexpr->cursor_name)
cursor_name = cexpr->cursor_name;
else
cursor_name = fetch_param_value(econtext, cexpr->cursor_param);
/* Fetch table name for possible use in error messages */
table_name = get_rel_name(table_oid);
@ -100,16 +114,54 @@ execCurrentOf(char *cursor_name, Oid table_oid,
if (TupIsNull(scanstate->ss_ScanTupleSlot))
return false;
tup = scanstate->ss_ScanTupleSlot->tts_tuple;
if (tup == NULL)
elog(ERROR, "CURRENT OF applied to non-materialized tuple");
Assert(tup->t_tableOid == table_oid);
/* Use slot_getattr to catch any possible mistakes */
tuple_tableoid = DatumGetObjectId(slot_getattr(scanstate->ss_ScanTupleSlot,
TableOidAttributeNumber,
&lisnull));
Assert(!lisnull);
tuple_tid = (ItemPointer)
DatumGetPointer(slot_getattr(scanstate->ss_ScanTupleSlot,
SelfItemPointerAttributeNumber,
&lisnull));
Assert(!lisnull);
*current_tid = tup->t_self;
Assert(tuple_tableoid == table_oid);
*current_tid = *tuple_tid;
return true;
}
/*
* fetch_param_value
*
* Fetch the string value of a param, verifying it is of type REFCURSOR.
*/
static char *
fetch_param_value(ExprContext *econtext, int paramId)
{
ParamListInfo paramInfo = econtext->ecxt_param_list_info;
if (paramInfo &&
paramId > 0 && paramId <= paramInfo->numParams)
{
ParamExternData *prm = &paramInfo->params[paramId - 1];
if (OidIsValid(prm->ptype) && !prm->isnull)
{
Assert(prm->ptype == REFCURSOROID);
/* We know that refcursor uses text's I/O routines */
return DatumGetCString(DirectFunctionCall1(textout,
prm->value));
}
}
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("no value found for parameter %d", paramId)));
return NULL;
}
/*
* search_plan_tree
*