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Reorder subskiplsn in pg_subscription to avoid alignment issues.

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The column 'subskiplsn' uses TYPALIGN_DOUBLE (which has 4 bytes alignment
on AIX) for storage. But the C Struct (Form_pg_subscription) has 8-byte
alignment for this field, so retrieving it from storage causes an
unaligned read.

To fix this, we rearranged the 'subskiplsn' column in the catalog so that
it naturally comes at an 8-byte boundary.

We have fixed a similar problem in commit f3b421da5f. This patch adds a
test to avoid a similar mistake in the future.

Reported-by: Noah Misch
Diagnosed-by: Noah Misch, Masahiko Sawada, Amit Kapila
Author: Masahiko Sawada
Reviewed-by: Noah Misch, Amit Kapila
Discussion: https://postgr.es/m/20220401074423.GC3682158@rfd.leadboat.com
	    https://postgr.es/m/CAD21AoDeScrsHhLyEPYqN3sydg6PxAPVBboK=30xJfUVihNZDA@mail.gmail.com
This commit is contained in:
Amit Kapila
2022-04-07 09:39:25 +05:30
parent e41aed674f
commit 79b716cfb7
11 changed files with 130 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
src/backend/catalog/pg_subscription.c
View File

@@ -63,6 +63,7 @@ GetSubscription(Oid subid, bool missing_ok)
sub = (Subscription *) palloc(sizeof(Subscription));
sub->oid = subid;
sub->dbid = subform->subdbid;
sub->skiplsn = subform->subskiplsn;
sub->name = pstrdup(NameStr(subform->subname));
sub->owner = subform->subowner;
sub->enabled = subform->subenabled;
@@ -70,7 +71,6 @@ GetSubscription(Oid subid, bool missing_ok)
sub->stream = subform->substream;
sub->twophasestate = subform->subtwophasestate;
sub->disableonerr = subform->subdisableonerr;
sub->skiplsn = subform->subskiplsn;
/* Get conninfo */
datum = SysCacheGetAttr(SUBSCRIPTIONOID,

4
src/backend/catalog/system_views.sql
View File

@@ -1285,8 +1285,8 @@ REVOKE ALL ON pg_replication_origin_status FROM public;
-- All columns of pg_subscription except subconninfo are publicly readable.
REVOKE ALL ON pg_subscription FROM public;
GRANT SELECT (oid, subdbid, subname, subowner, subenabled, subbinary,
substream, subtwophasestate, subdisableonerr, subskiplsn, subslotname,
GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
subbinary, substream, subtwophasestate, subdisableonerr, subslotname,
subsynccommit, subpublications)
ON pg_subscription TO public;

2
src/backend/commands/subscriptioncmds.c
View File

@@ -596,6 +596,7 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
Anum_pg_subscription_oid);
values[Anum_pg_subscription_oid - 1] = ObjectIdGetDatum(subid);
values[Anum_pg_subscription_subdbid - 1] = ObjectIdGetDatum(MyDatabaseId);
values[Anum_pg_subscription_subskiplsn - 1] = LSNGetDatum(InvalidXLogRecPtr);
values[Anum_pg_subscription_subname - 1] =
DirectFunctionCall1(namein, CStringGetDatum(stmt->subname));
values[Anum_pg_subscription_subowner - 1] = ObjectIdGetDatum(owner);
@@ -607,7 +608,6 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
LOGICALREP_TWOPHASE_STATE_PENDING :
LOGICALREP_TWOPHASE_STATE_DISABLED);
values[Anum_pg_subscription_subdisableonerr - 1] = BoolGetDatum(opts.disableonerr);
values[Anum_pg_subscription_subskiplsn - 1] = LSNGetDatum(InvalidXLogRecPtr);
values[Anum_pg_subscription_subconninfo - 1] =
CStringGetTextDatum(conninfo);
if (opts.slot_name)