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Fix no-longer-valid shortcuts in expression_returns_set().

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expression_returns_set() used to short-circuit its recursion upon
seeing certain node types, such as DistinctExpr, that it knew the
executor did not support set-valued arguments for.  That was never
inherent, though, just a reflection of laziness in execQual.c.
With the new implementation of SRFs there is no reason to think
that any scalar-valued expression node could not have a set-valued
subexpression, except for AggRefs and WindowFuncs where we know there
is a parser check rejecting it.  And indeed, the shortcut causes
unexpected failures for cases such as a SRF underneath DistinctExpr,
because the planner stops looking for SRFs too soon.

Discussion: https://postgr.es/m/5259.1497044025@sss.pgh.pa.us
This commit is contained in:
Tom Lane 2017-06-14 11:10:05 -04:00
parent a571c7f661
commit 8e72239e9d
3 changed files with 10 additions and 29 deletions
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30
src/backend/nodes/nodeFuncs.c
View File

@ -694,39 +694,11 @@ expression_returns_set_walker(Node *node, void *context)
/* else fall through to check args */
}
/* Avoid recursion for some cases that can't return a set */
/* Avoid recursion for some cases that parser checks not to return a set */
if (IsA(node, Aggref))
return false;
if (IsA(node, WindowFunc))
return false;
if (IsA(node, DistinctExpr))
return false;
if (IsA(node, NullIfExpr))
return false;
if (IsA(node, ScalarArrayOpExpr))
return false;
if (IsA(node, BoolExpr))
return false;
if (IsA(node, SubLink))
return false;
if (IsA(node, SubPlan))
return false;
if (IsA(node, AlternativeSubPlan))
return false;
if (IsA(node, ArrayExpr))
return false;
if (IsA(node, RowExpr))
return false;
if (IsA(node, RowCompareExpr))
return false;
if (IsA(node, CoalesceExpr))
return false;
if (IsA(node, MinMaxExpr))
return false;
if (IsA(node, SQLValueFunction))
return false;
if (IsA(node, XmlExpr))
return false;
return expression_tree_walker(node, expression_returns_set_walker,
context);

8
src/test/regress/expected/tsrf.out
View File

@ -443,6 +443,14 @@ SELECT int4mul(generate_series(1,2), 10);
20
(2 rows)
SELECT generate_series(1,3) IS DISTINCT FROM 2;
?column?
----------
t
f
t
(3 rows)
-- but SRFs in function RTEs must be at top level (annoying restriction)
SELECT * FROM int4mul(generate_series(1,2), 10);
ERROR: set-returning functions must appear at top level of FROM

1
src/test/regress/sql/tsrf.sql
View File

@ -98,6 +98,7 @@ VALUES(1, generate_series(1,2));
-- We allow tSRFs that are not at top level
SELECT int4mul(generate_series(1,2), 10);
SELECT generate_series(1,3) IS DISTINCT FROM 2;
-- but SRFs in function RTEs must be at top level (annoying restriction)
SELECT * FROM int4mul(generate_series(1,2), 10);