Hello,
At Mon, 25 Jul 2016 18:21:27 +0900, Amit Langote
<langote_amit...@lab.ntt.co.jp> wrote in
<96fb8bca-57f5-e5a8-9630-79d4fc5b2...@lab.ntt.co.jp>
>
> Hello,
>
> On 2016/07/25 17:18, Kyotaro HORIGUCHI wrote:
> >
> > - Remove ccvalid condition from equalTupleDescs() to reduce
> > unnecessary cache invalidation or tuple rebuilding.
>
> The following commit introduced the ccvalid check:
>
> """
> commit c31305de5f5a4880b0ba2f5983025ef0210a3b2a
> Author: Noah Misch <n...@leadboat.com>
> Date: Sun Mar 23 02:13:43 2014 -0400
>
> Address ccvalid/ccnoinherit in TupleDesc support functions.
>
> equalTupleDescs() neglected both of these ConstrCheck fields, and
> CreateTupleDescCopyConstr() neglected ccnoinherit. At this time, the
> only known behavior defect resulting from these omissions is constraint
> exclusion disregarding a CHECK constraint validated by an ALTER TABLE
> VALIDATE CONSTRAINT statement issued earlier in the same transaction.
> Back-patch to 9.2, where these fields were introduced.
> """
Wow.. Missed the obvious thing. Certainly relation cache must be
invalidated by a change of ccvalidated as the commit message.
> So, apparently RelationClearRelation() does intend to discard a cached
> TupleDesc if ccvalid changed in a transaction. Whereas,
> acquire_inherited_sample_rows() does not seem to depend on ccvalid being
> equal or not (or any member of TupleConstr for that matter). So maybe,
> instead of simply discarding the check (which does serve a purpose), we
> could make equalTupleDescs() parameterized on whether we want TupleConstr
> equality check to be performed or not. RelationClearRelation() can ask
> for the check to be performed by passing true for the parameter whereas
> acquire_inherited_sample_rows() and other callers can pass false. Perhaps
> something like the attached.
Hmm. It should resolve the problem. But the two comparisons seem
to be separate things. Constraints is not a part of tuple
description. relcache seems to be making misusage of the equality
of tuple descriptors.
So, how about splitting the original equalTupleDescs into
equalTupleDescs and equalTupleConstraints ?
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
>From 5a1d570ac327702fea19ed18198efeb02632a2f3 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyot...@lab.ntt.co.jp>
Date: Tue, 26 Jul 2016 11:02:48 +0900
Subject: [PATCH] Split equalTupleDescs into two functions.
equalTupleDescs intends to the two given tuple descriptors are
compatible on generating a tuple. Comaprison on constraints are
required to invalidate cache but it is a separate matter. So split it
into two new functions equalTupleDescs and equalTupleConstraints.
---
src/backend/access/common/tupdesc.c | 14 ++++++++++++++
src/include/access/tupdesc.h | 1 +
2 files changed, 15 insertions(+)
diff --git a/src/backend/access/common/tupdesc.c b/src/backend/access/common/tupdesc.c
index b56d0e3..1e42c87 100644
--- a/src/backend/access/common/tupdesc.c
+++ b/src/backend/access/common/tupdesc.c
@@ -411,6 +411,19 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
/* attacl, attoptions and attfdwoptions are not even present... */
}
+ return true;
+}
+
+/*
+ * Compare constraints between two TupleDesc structures
+ */
+bool
+equalTupleConstraints(TupleDesc tupdesc1, TupleDesc tupdesc2)
+{
+ int i,
+ j,
+ n;
+
if (tupdesc1->constr != NULL)
{
TupleConstr *constr1 = tupdesc1->constr;
@@ -470,6 +483,7 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
}
else if (tupdesc2->constr != NULL)
return false;
+
return true;
}
diff --git a/src/include/access/tupdesc.h b/src/include/access/tupdesc.h
index de18f74..58fa466 100644
--- a/src/include/access/tupdesc.h
+++ b/src/include/access/tupdesc.h
@@ -111,6 +111,7 @@ extern void DecrTupleDescRefCount(TupleDesc tupdesc);
} while (0)
extern bool equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
+extern bool equalTupleConstraints(TupleDesc tupdesc1, TupleDesc tupdesc2);
extern void TupleDescInitEntry(TupleDesc desc,
AttrNumber attributeNumber,
--
1.8.3.1
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