On Mon, Apr 2, 2018 at 1:40 AM, Andres Freund <and...@anarazel.de> wrote:
> Hi,
>
> On 2018-02-26 17:20:05 +0530, Ashutosh Bapat wrote:
>> In a multi-level partitioned table, a parent whole-row reference gets
>> translated into nested ConvertRowtypeExpr with child whole-row
>> reference as the leaf. During the execution, the child whole-row
>> reference gets translated into all all intermediate parents' whole-row
>> references, ultimately represented as parent's whole-row reference.
>> AFAIU, the intermediate translations are unnecessary. The leaf child
>> whole-row can be directly translated into top parent's whole-row
>> reference. Here's a WIP patch which does that by eliminating
>> intermediate ConvertRowtypeExprs during ExecInitExprRec().
>
> Why is this done appropriately at ExecInitExpr() time, rather than at
> plan time? Seems like eval_const_expressions() would be a bit more
> appropriate (being badly named aside...)?
That seems to be a better idea. Here's patch.
--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company
From b99ae826931516a7c6ad981435e8ac9ef754f15e Mon Sep 17 00:00:00 2001
From: Ashutosh Bapat <ashutosh.ba...@enterprisedb.com>
Date: Tue, 3 Apr 2018 09:00:19 +0530
Subject: [PATCH] Optimize nested ConvertRowtypeExprs
A ConvertRowtypeExprs 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, reviewed by Andres Freund.
---
src/backend/optimizer/util/clauses.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index ed6b680..3af5033 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -3657,6 +3657,31 @@ eval_const_expressions_mutator(Node *node,
context);
}
break;
+ case T_ConvertRowtypeExpr:
+ {
+ ConvertRowtypeExpr *cre = castNode(ConvertRowtypeExpr, node);
+ Expr *arg = cre->arg;
+ ConvertRowtypeExpr *newcre;
+
+ /*
+ * In case of a nested ConvertRowtypeExpr, we can convert the
+ * leaf row directly to the topmost row format without any
+ * intermediate conversions.
+ */
+ Assert(arg != NULL);
+ while (IsA(arg, ConvertRowtypeExpr))
+ arg = castNode(ConvertRowtypeExpr, arg)->arg;
+
+ newcre = makeNode(ConvertRowtypeExpr);
+ newcre->arg = arg;
+ newcre->resulttype = cre->resulttype;
+ newcre->convertformat = cre->convertformat;
+ newcre->location = newcre->location;
+
+ if (IsA(arg, Const))
+ return ece_evaluate_expr((Node *) newcre);
+ return (Node *) newcre;
+ }
default:
break;
}
--
1.7.9.5
