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Make ARRAY(SELECT ...) return an empty array, rather than a NULL, when the

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sub-select returns zero rows.  Per complaint from Jens Schicke.  Since this
is more in the nature of a definition change than a bug, not back-patched.
This commit is contained in:
Tom Lane 2007-08-26 21:44:25 +00:00
parent 75d5f6fe79
commit 67bf7b919e
3 changed files with 52 additions and 41 deletions
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77
src/backend/executor/nodeSubplan.c
View file

@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.89 2007/05/17 19:35:08 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.90 2007/08/26 21:44:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -259,10 +259,14 @@ ExecScanSubPlan(SubPlanState *node,
* ROWCOMPARE_SUBLINK.
*
* For EXPR_SUBLINK we require the subplan to produce no more than one
* tuple, else an error is raised. For ARRAY_SUBLINK we allow the subplan
* to produce more than one tuple. In either case, if zero tuples are
* produced, we return NULL. Assuming we get a tuple, we just use its
* first column (there can be only one non-junk column in this case).
* tuple, else an error is raised. If zero tuples are produced, we return
* NULL. Assuming we get a tuple, we just use its first column (there can
* be only one non-junk column in this case).
*
* For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
* and form an array of the first column's values. Note in particular
* that we produce a zero-element array if no tuples are produced (this
* is a change from pre-8.3 behavior of returning NULL).
*/
result = BoolGetDatum(subLinkType == ALL_SUBLINK);
*isNull = false;
@ -317,10 +321,10 @@ ExecScanSubPlan(SubPlanState *node,
found = true;
/* stash away current value */
Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
dvalue = slot_getattr(slot, 1, &disnull);
astate = accumArrayResult(astate, dvalue, disnull,
tdesc->attrs[0]->atttypid,
oldcontext);
subplan->firstColType, oldcontext);
/* keep scanning subplan to collect all values */
continue;
}
@ -385,29 +389,30 @@ ExecScanSubPlan(SubPlanState *node,
}
}
if (!found)
MemoryContextSwitchTo(oldcontext);
if (subLinkType == ARRAY_SUBLINK)
{
/* We return the result in the caller's context */
if (astate != NULL)
result = makeArrayResult(astate, oldcontext);
else
result = PointerGetDatum(construct_empty_array(subplan->firstColType));
}
else if (!found)
{
/*
* deal with empty subplan result. result/isNull were previously
* initialized correctly for all sublink types except EXPR, ARRAY, and
* initialized correctly for all sublink types except EXPR and
* ROWCOMPARE; for those, return NULL.
*/
if (subLinkType == EXPR_SUBLINK ||
subLinkType == ARRAY_SUBLINK ||
subLinkType == ROWCOMPARE_SUBLINK)
{
result = (Datum) 0;
*isNull = true;
}
}
else if (subLinkType == ARRAY_SUBLINK)
{
Assert(astate != NULL);
/* We return the result in the caller's context */
result = makeArrayResult(astate, oldcontext);
}
MemoryContextSwitchTo(oldcontext);
return result;
}
@ -938,10 +943,10 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
found = true;
/* stash away current value */
Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
dvalue = slot_getattr(slot, 1, &disnull);
astate = accumArrayResult(astate, dvalue, disnull,
tdesc->attrs[0]->atttypid,
oldcontext);
subplan->firstColType, oldcontext);
/* keep scanning subplan to collect all values */
continue;
}
@ -980,7 +985,25 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
}
}
if (!found)
if (subLinkType == ARRAY_SUBLINK)
{
/* There can be only one param... */
int paramid = linitial_int(subplan->setParam);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
prm->execPlan = NULL;
/* We build the result in query context so it won't disappear */
if (astate != NULL)
prm->value = makeArrayResult(astate,
econtext->ecxt_per_query_memory);
else
{
MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
prm->value = PointerGetDatum(construct_empty_array(subplan->firstColType));
}
prm->isnull = false;
}
else if (!found)
{
if (subLinkType == EXISTS_SUBLINK)
{
@ -1005,18 +1028,6 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
}
}
}
else if (subLinkType == ARRAY_SUBLINK)
{
/* There can be only one param... */
int paramid = linitial_int(subplan->setParam);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
Assert(astate != NULL);
prm->execPlan = NULL;
/* We build the result in query context so it won't disappear */
prm->value = makeArrayResult(astate, econtext->ecxt_per_query_memory);
prm->isnull = false;
}
MemoryContextSwitchTo(oldcontext);
}

10
src/backend/optimizer/plan/subselect.c
View file

@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.123 2007/07/18 21:40:57 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.124 2007/08/26 21:44:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -208,10 +208,10 @@ generate_new_param(PlannerInfo *root, Oid paramtype, int32 paramtypmod)
/*
* Get the datatype of the first column of the plan's output.
*
* This is a hack to support exprType(), which doesn't have any way to get
* at the plan associated with a SubPlan node. We really only need the value
* for EXPR_SUBLINK and ARRAY_SUBLINK subplans, but for consistency we set
* it always.
* This is stored for ARRAY_SUBLINK and for exprType(), which doesn't have any
* way to get at the plan associated with a SubPlan node. We really only need
* the value for EXPR_SUBLINK and ARRAY_SUBLINK subplans, but for consistency
* we set it always.
*/
static Oid
get_first_col_type(Plan *plan)

6
src/include/nodes/primnodes.h
View file

@ -10,7 +10,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.132 2007/06/11 22:22:42 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.133 2007/08/26 21:44:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -388,7 +388,7 @@ typedef struct BoolExpr
* results. ALL and ANY combine the per-row results using AND and OR
* semantics respectively.
* ARRAY requires just one target column, and creates an array of the target
* column's type using one or more rows resulting from the subselect.
* column's type using any number of rows resulting from the subselect.
*
* SubLink is classed as an Expr node, but it is not actually executable;
* it must be replaced in the expression tree by a SubPlan node during
@ -468,7 +468,7 @@ typedef struct SubPlan
List *paramIds; /* IDs of Params embedded in the above */
/* Identification of the Plan tree to use: */
int plan_id; /* Index (from 1) in PlannedStmt.subplans */
/* Extra data saved for the convenience of exprType(): */
/* Extra data useful for determining subplan's output type: */
Oid firstColType; /* Type of first column of subplan result */
/* Information about execution strategy: */
bool useHashTable; /* TRUE to store subselect output in a hash