>>>>> "Andrew" == Andrew Gierth <and...@tao11.riddles.org.uk> writes:
Andrew> I'm going to pull all this together and commit it shortly.
Here's the patch with my edits (more comments and the while/if change).
I'll commit this in due course unless I hear otherwise.
--
Andrew (irc:RhodiumToad)
>From 9cc81cea6de41140fe361bff375190bfdd188ae9 Mon Sep 17 00:00:00 2001
From: Andrew Gierth <rhodiumt...@postgresql.org>
Date: Tue, 6 Nov 2018 14:19:40 +0000
Subject: [PATCH] Optimize nested ConvertRowtypeExpr nodes.
A ConvertRowtypeExpr is used to translate a whole-row reference of a
child to that of a parent. The planner produces nested
ConvertRowtypeExpr while translating whole-row reference of a leaf
partition in a multi-level partition hierarchy. Executor then
translates the whole-row reference from the leaf partition into all
the intermediate parent's whole-row references before arriving at the
final whole-row reference. It could instead translate the whole-row
reference from the leaf partition directly to the top-most parent's
whole-row reference skipping any intermediate translations.
Ashutosh Bapat, with tests by Kyotaro Horiguchi and some
editorialization by me. Reviewed by Andres Freund, Pavel Stehule,
Kyotaro Horiguchi, Dmitry Dolgov.
---
src/backend/optimizer/util/clauses.c | 46 +++++++++++++++++++++++++++++++++++
src/test/regress/expected/inherit.out | 18 ++++++++++++++
src/test/regress/sql/inherit.sql | 5 ++++
3 files changed, 69 insertions(+)
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 21bf5dea9c..d13c3ac895 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -3716,6 +3716,52 @@ eval_const_expressions_mutator(Node *node,
context);
}
break;
+ case T_ConvertRowtypeExpr:
+ {
+ ConvertRowtypeExpr *cre = castNode(ConvertRowtypeExpr, node);
+ Node *arg;
+ ConvertRowtypeExpr *newcre;
+
+ arg = eval_const_expressions_mutator((Node *) cre->arg,
+ context);
+
+ newcre = makeNode(ConvertRowtypeExpr);
+ newcre->resulttype = cre->resulttype;
+ newcre->convertformat = cre->convertformat;
+ newcre->location = cre->location;
+
+ /*
+ * In case of a nested ConvertRowtypeExpr, we can convert the
+ * leaf row directly to the topmost row format without any
+ * intermediate conversions. (This works because
+ * ConvertRowtypeExpr is used only for child->parent
+ * conversion in inheritance trees, which works by exact match
+ * of column name, and a column absent in an intermediate
+ * result can't be present in the final result.)
+ *
+ * No need to check more than one level deep, because the
+ * above recursion will have flattened anything else.
+ */
+ if (arg != NULL && IsA(arg, ConvertRowtypeExpr))
+ {
+ ConvertRowtypeExpr *argcre = castNode(ConvertRowtypeExpr, arg);
+
+ arg = (Node *) argcre->arg;
+
+ /*
+ * Make sure an outer implicit conversion can't hide an
+ * inner explicit one.
+ */
+ if (newcre->convertformat == COERCE_IMPLICIT_CAST)
+ newcre->convertformat = argcre->convertformat;
+ }
+
+ newcre->arg = (Expr *) arg;
+
+ if (arg != NULL && IsA(arg, Const))
+ return ece_evaluate_expr((Node *) newcre);
+ return (Node *) newcre;
+ }
default:
break;
}
diff --git a/src/test/regress/expected/inherit.out b/src/test/regress/expected/inherit.out
index d768e5df2c..1e00c849f3 100644
--- a/src/test/regress/expected/inherit.out
+++ b/src/test/regress/expected/inherit.out
@@ -764,6 +764,8 @@ NOTICE: drop cascades to table c1
-- tables. See the pgsql-hackers thread beginning Dec. 4/04
create table base (i integer);
create table derived () inherits (base);
+create table more_derived (like derived, b int) inherits (derived);
+NOTICE: merging column "i" with inherited definition
insert into derived (i) values (0);
select derived::base from derived;
derived
@@ -777,6 +779,22 @@ select NULL::derived::base;
(1 row)
+-- remove redundant conversions.
+explain (verbose on, costs off) select row(i, b)::more_derived::derived::base from more_derived;
+ QUERY PLAN
+-------------------------------------------
+ Seq Scan on public.more_derived
+ Output: (ROW(i, b)::more_derived)::base
+(2 rows)
+
+explain (verbose on, costs off) select (1, 2)::more_derived::derived::base;
+ QUERY PLAN
+-----------------------
+ Result
+ Output: '(1)'::base
+(2 rows)
+
+drop table more_derived;
drop table derived;
drop table base;
create table p1(ff1 int);
diff --git a/src/test/regress/sql/inherit.sql b/src/test/regress/sql/inherit.sql
index e8b6448f3c..afc72f47bc 100644
--- a/src/test/regress/sql/inherit.sql
+++ b/src/test/regress/sql/inherit.sql
@@ -237,9 +237,14 @@ drop table p1 cascade;
-- tables. See the pgsql-hackers thread beginning Dec. 4/04
create table base (i integer);
create table derived () inherits (base);
+create table more_derived (like derived, b int) inherits (derived);
insert into derived (i) values (0);
select derived::base from derived;
select NULL::derived::base;
+-- remove redundant conversions.
+explain (verbose on, costs off) select row(i, b)::more_derived::derived::base from more_derived;
+explain (verbose on, costs off) select (1, 2)::more_derived::derived::base;
+drop table more_derived;
drop table derived;
drop table base;
--
2.11.1
