On 2019-02-06 23:15, Peter Eisentraut wrote:
> On 05/02/2019 17:20, Tom Lane wrote:
>> What I *don't* like about the proposed patch is that it installs a
>> new, different comparison rule for the ON UPDATE CASCADE case only.
>> If we were to go in this direction, I'd think we should try to use
>> the same comparison rule for all FK row comparisons.
>
> That's easy to change. I had it like that in earlier versions of the
> patch. I agree it would be better for consistency, but it would create
> some cases where we do unnecessary extra work.
Updated patch with this change made, and some conflicts resolved.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
From d8615fe224eed4747682e88202faad1251c317f6 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Tue, 5 Feb 2019 16:27:00 +0100
Subject: [PATCH v2 1/2] Test case for keys that "look" different but compare
as equal
---
src/test/regress/expected/foreign_key.out | 34 +++++++++++++++++++++++
src/test/regress/sql/foreign_key.sql | 20 +++++++++++++
2 files changed, 54 insertions(+)
diff --git a/src/test/regress/expected/foreign_key.out
b/src/test/regress/expected/foreign_key.out
index bf2c91d9f0..a68d055e40 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -1474,6 +1474,40 @@ delete from pktable2 where f1 = 1;
alter table fktable2 drop constraint fktable2_f1_fkey;
ERROR: cannot ALTER TABLE "pktable2" because it has pending trigger events
commit;
+drop table pktable2, fktable2;
+--
+-- Test keys that "look" different but compare as equal
+--
+create table pktable2 (a float8, b float8, primary key (a, b));
+create table fktable2 (x float8, y float8, foreign key (x, y) references
pktable2 (a, b) on update cascade);
+insert into pktable2 values ('-0', '-0');
+insert into fktable2 values ('-0', '-0');
+select * from pktable2;
+ a | b
+----+----
+ -0 | -0
+(1 row)
+
+select * from fktable2;
+ x | y
+----+----
+ -0 | -0
+(1 row)
+
+update pktable2 set a = '0' where a = '-0';
+select * from pktable2;
+ a | b
+---+----
+ 0 | -0
+(1 row)
+
+-- buggy: did not update fktable2.x
+select * from fktable2;
+ x | y
+----+----
+ -0 | -0
+(1 row)
+
drop table pktable2, fktable2;
--
-- Foreign keys and partitioned tables
diff --git a/src/test/regress/sql/foreign_key.sql
b/src/test/regress/sql/foreign_key.sql
index c8d1214d02..c1fc7d30b1 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1106,6 +1106,26 @@ CREATE TEMP TABLE tasks (
drop table pktable2, fktable2;
+--
+-- Test keys that "look" different but compare as equal
+--
+create table pktable2 (a float8, b float8, primary key (a, b));
+create table fktable2 (x float8, y float8, foreign key (x, y) references
pktable2 (a, b) on update cascade);
+
+insert into pktable2 values ('-0', '-0');
+insert into fktable2 values ('-0', '-0');
+
+select * from pktable2;
+select * from fktable2;
+
+update pktable2 set a = '0' where a = '-0';
+
+select * from pktable2;
+-- buggy: did not update fktable2.x
+select * from fktable2;
+
+drop table pktable2, fktable2;
+
--
-- Foreign keys and partitioned tables
base-commit: f2d84a4a6b4ec891a0a52f583ed5aa081c71acc6
--
2.21.0
From f9f05aceaed972147719345c65cce9222c50ef5e Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Mon, 11 Mar 2019 12:55:22 +0100
Subject: [PATCH v2 2/2] Fix optimization of foreign-key on update actions
In RI_FKey_pk_upd_check_required(), we check among other things
whether the old and new key are equal, so that we don't need to run
cascade actions when nothing has actually changed. This was using the
equality operator. But the effect of this is that if a value in the
primary key is changed to one that "looks" different but compares as
equal, the update is not propagated. (Examples are float -0 and 0 and
case-insensitive text.) This appears to violate the SQL standard, and
it also behaves inconsistently if in a multicolumn key another key is
also updated that would cause the row to compare as not equal.
To fix, if we are looking at the PK table in ri_KeysEqual(), then do a
bytewise comparison similar to record_image_eq() instead of using the
equality operators. This only makes a difference for ON UPDATE
CASCADE, but for consistency we treat all changes to the PK the same. For
the FK table, we continue to use the equality operators.
Discussion:
https://www.postgresql.org/message-id/flat/3326fc2e-bc02-d4c5-e3e5-e54da466e...@2ndquadrant.com
---
src/backend/utils/adt/datum.c | 57 +++++++++++++++++++++++
src/backend/utils/adt/ri_triggers.c | 40 ++++++++++------
src/backend/utils/adt/rowtypes.c | 41 +---------------
src/include/utils/datum.h | 9 ++++
src/test/regress/expected/foreign_key.out | 8 ++--
src/test/regress/sql/foreign_key.sql | 2 +-
6 files changed, 100 insertions(+), 57 deletions(-)
diff --git a/src/backend/utils/adt/datum.c b/src/backend/utils/adt/datum.c
index af5944d395..81ea5a48e5 100644
--- a/src/backend/utils/adt/datum.c
+++ b/src/backend/utils/adt/datum.c
@@ -42,6 +42,8 @@
#include "postgres.h"
+#include "access/tuptoaster.h"
+#include "fmgr.h"
#include "utils/datum.h"
#include "utils/expandeddatum.h"
@@ -251,6 +253,61 @@ datumIsEqual(Datum value1, Datum value2, bool typByVal,
int typLen)
return res;
}
+/*-------------------------------------------------------------------------
+ * datum_image_eq
+ *
+ * Compares two datums for identical contents, based on byte images. Return
+ * true if the two datums are equal, false otherwise.
+ *-------------------------------------------------------------------------
+ */
+bool
+datum_image_eq(Datum value1, Datum value2, bool typByVal, int typLen)
+{
+ bool result = true;
+
+ if (typLen == -1)
+ {
+ Size len1,
+ len2;
+
+ len1 = toast_raw_datum_size(value1);
+ len2 = toast_raw_datum_size(value2);
+ /* No need to de-toast if lengths don't match. */
+ if (len1 != len2)
+ result = false;
+ else
+ {
+ struct varlena *arg1val;
+ struct varlena *arg2val;
+
+ arg1val = PG_DETOAST_DATUM_PACKED(value1);
+ arg2val = PG_DETOAST_DATUM_PACKED(value2);
+
+ result = (memcmp(VARDATA_ANY(arg1val),
+ VARDATA_ANY(arg2val),
+ len1 - VARHDRSZ) == 0);
+
+ /* Only free memory if it's a copy made here. */
+ if ((Pointer) arg1val != (Pointer) value1)
+ pfree(arg1val);
+ if ((Pointer) arg2val != (Pointer) value2)
+ pfree(arg2val);
+ }
+ }
+ else if (typByVal)
+ {
+ result = (value1 == value2);
+ }
+ else
+ {
+ result = (memcmp(DatumGetPointer(value1),
+ DatumGetPointer(value2),
+ typLen) == 0);
+ }
+
+ return result;
+}
+
/*-------------------------------------------------------------------------
* datumEstimateSpace
*
diff --git a/src/backend/utils/adt/ri_triggers.c
b/src/backend/utils/adt/ri_triggers.c
index ef04fa5009..0a6548a797 100644
--- a/src/backend/utils/adt/ri_triggers.c
+++ b/src/backend/utils/adt/ri_triggers.c
@@ -42,6 +42,7 @@
#include "storage/bufmgr.h"
#include "utils/acl.h"
#include "utils/builtins.h"
+#include "utils/datum.h"
#include "utils/fmgroids.h"
#include "utils/guc.h"
#include "utils/inval.h"
@@ -2419,18 +2420,11 @@ ri_KeysEqual(Relation rel, TupleTableSlot *oldslot,
TupleTableSlot *newslot,
const RI_ConstraintInfo *riinfo, bool rel_is_pk)
{
const int16 *attnums;
- const Oid *eq_oprs;
if (rel_is_pk)
- {
attnums = riinfo->pk_attnums;
- eq_oprs = riinfo->pp_eq_oprs;
- }
else
- {
attnums = riinfo->fk_attnums;
- eq_oprs = riinfo->ff_eq_oprs;
- }
/* XXX: could be worthwhile to fetch all necessary attrs at once */
for (int i = 0; i < riinfo->nkeys; i++)
@@ -2453,12 +2447,32 @@ ri_KeysEqual(Relation rel, TupleTableSlot *oldslot,
TupleTableSlot *newslot,
if (isnull)
return false;
- /*
- * Compare them with the appropriate equality operator.
- */
- if (!ri_AttributesEqual(eq_oprs[i], RIAttType(rel, attnums[i]),
- oldvalue,
newvalue))
- return false;
+ if (rel_is_pk)
+ {
+ /*
+ * If we are looking at the PK table, then do a bytewise
+ * comparison. We must propagate PK changes if the
value is
+ * changed to one that "looks" different but would
compare as
+ * equal using the equality operator. This only makes a
+ * difference for ON UPDATE CASCADE, but for
consistency we treat
+ * all changes to the PK the same.
+ */
+ Form_pg_attribute att =
TupleDescAttr(oldslot->tts_tupleDescriptor, attnums[i] - 1);
+
+ if (!datum_image_eq(oldvalue, newvalue, att->attbyval,
att->attlen))
+ return false;
+ }
+ else
+ {
+ /*
+ * For the FK table, compare with the appropriate
equality
+ * operator. Changes that compare equal will still
satisfy the
+ * constraint after the update.
+ */
+ if (!ri_AttributesEqual(riinfo->ff_eq_oprs[i],
RIAttType(rel, attnums[i]),
+
oldvalue, newvalue))
+ return false;
+ }
}
return true;
diff --git a/src/backend/utils/adt/rowtypes.c b/src/backend/utils/adt/rowtypes.c
index 5bbf568610..aa7ec8735c 100644
--- a/src/backend/utils/adt/rowtypes.c
+++ b/src/backend/utils/adt/rowtypes.c
@@ -23,6 +23,7 @@
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "utils/builtins.h"
+#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/typcache.h"
@@ -1671,45 +1672,7 @@ record_image_eq(PG_FUNCTION_ARGS)
}
/* Compare the pair of elements */
- if (att1->attlen == -1)
- {
- Size len1,
- len2;
-
- len1 = toast_raw_datum_size(values1[i1]);
- len2 = toast_raw_datum_size(values2[i2]);
- /* No need to de-toast if lengths don't match.
*/
- if (len1 != len2)
- result = false;
- else
- {
- struct varlena *arg1val;
- struct varlena *arg2val;
-
- arg1val =
PG_DETOAST_DATUM_PACKED(values1[i1]);
- arg2val =
PG_DETOAST_DATUM_PACKED(values2[i2]);
-
- result = (memcmp(VARDATA_ANY(arg1val),
-
VARDATA_ANY(arg2val),
- len1 -
VARHDRSZ) == 0);
-
- /* Only free memory if it's a copy made
here. */
- if ((Pointer) arg1val != (Pointer)
values1[i1])
- pfree(arg1val);
- if ((Pointer) arg2val != (Pointer)
values2[i2])
- pfree(arg2val);
- }
- }
- else if (att1->attbyval)
- {
- result = (values1[i1] == values2[i2]);
- }
- else
- {
- result = (memcmp(DatumGetPointer(values1[i1]),
-
DatumGetPointer(values2[i2]),
- att1->attlen)
== 0);
- }
+ result = datum_image_eq(values1[i1], values2[i2],
att1->attbyval, att2->attlen);
if (!result)
break;
}
diff --git a/src/include/utils/datum.h b/src/include/utils/datum.h
index 7b913578ab..4365bf06e6 100644
--- a/src/include/utils/datum.h
+++ b/src/include/utils/datum.h
@@ -46,6 +46,15 @@ extern Datum datumTransfer(Datum value, bool typByVal, int
typLen);
extern bool datumIsEqual(Datum value1, Datum value2,
bool typByVal, int typLen);
+/*
+ * datum_image_eq
+ *
+ * Compares two datums for identical contents, based on byte images. Return
+ * true if the two datums are equal, false otherwise.
+ */
+extern bool datum_image_eq(Datum value1, Datum value2,
+ bool typByVal, int typLen);
+
/*
* Serialize and restore datums so that we can transfer them to parallel
* workers.
diff --git a/src/test/regress/expected/foreign_key.out
b/src/test/regress/expected/foreign_key.out
index a68d055e40..31f5739fcb 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -1501,11 +1501,11 @@ select * from pktable2;
0 | -0
(1 row)
--- buggy: did not update fktable2.x
+-- should update fktable2.x
select * from fktable2;
- x | y
-----+----
- -0 | -0
+ x | y
+---+----
+ 0 | -0
(1 row)
drop table pktable2, fktable2;
diff --git a/src/test/regress/sql/foreign_key.sql
b/src/test/regress/sql/foreign_key.sql
index c1fc7d30b1..dead30a0c1 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1121,7 +1121,7 @@ CREATE TEMP TABLE tasks (
update pktable2 set a = '0' where a = '-0';
select * from pktable2;
--- buggy: did not update fktable2.x
+-- should update fktable2.x
select * from fktable2;
drop table pktable2, fktable2;
--
2.21.0
