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Fix issues with wide tuples being updated and REPLICA IDENTITY FULL.

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When replica identity full is being used with a wide tuple (above 2^16
bytes after compression) it lead to errors and/or crashes during
decoding because the length field used to store such tuples doesn't
fit into the variable used to store the width in the WAL record.

To fix, discontinue use of xl_heap_header_len.t_len when decoding the
old tuple version, instead compute length of the old tuple by
subtracting the new tuple's length from the record length.

In newer version of postgres this issue is moot because the length is
stored by the new WAL machinery, instead of a xl_heap_header_len
struct.  A separate commit will forward-patch the regression test.

Reported-By: "anderson"
Discussion: http://postgr.es/m/20170105144819.f6i5o64vfvy4bn5i@alap3.anarazel.de
This commit is contained in:
Andres Freund
2017-08-05 14:32:01 -07:00
parent 8d05db3d8e
commit 23a2b818f5
4 changed files with 32 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
contrib/test_decoding/expected/toast.out
View File

@ -298,7 +298,13 @@ ALTER TABLE toasted_several REPLICA IDENTITY FULL;
ALTER TABLE toasted_several ALTER COLUMN toasted_key SET STORAGE EXTERNAL;
ALTER TABLE toasted_several ALTER COLUMN toasted_col1 SET STORAGE EXTERNAL;
ALTER TABLE toasted_several ALTER COLUMN toasted_col2 SET STORAGE EXTERNAL;
INSERT INTO toasted_several(toasted_key) VALUES(repeat('9876543210', 2000));
INSERT INTO toasted_several(toasted_key) VALUES(repeat('9876543210', 10000));
SELECT pg_column_size(toasted_key) > 2^16 FROM toasted_several;
?column?
----------
t
(1 row)
SELECT regexp_replace(data, '^(.{100}).*(.{100})$', '\1..\2') FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
regexp_replace
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

3
contrib/test_decoding/sql/toast.sql
View File

@ -274,7 +274,8 @@ ALTER TABLE toasted_several ALTER COLUMN toasted_key SET STORAGE EXTERNAL;
ALTER TABLE toasted_several ALTER COLUMN toasted_col1 SET STORAGE EXTERNAL;
ALTER TABLE toasted_several ALTER COLUMN toasted_col2 SET STORAGE EXTERNAL;
INSERT INTO toasted_several(toasted_key) VALUES(repeat('9876543210', 2000));
INSERT INTO toasted_several(toasted_key) VALUES(repeat('9876543210', 10000));
SELECT pg_column_size(toasted_key) > 2^16 FROM toasted_several;
SELECT regexp_replace(data, '^(.{100}).*(.{100})$', '\1..\2') FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');

8
src/backend/access/heap/heapam.c
View File

@ -7086,7 +7086,13 @@ log_heap_update(Relation reln, Buffer oldbuf,
/* We need to log a tuple identity */
if (old_key_tuple)
{
/* don't really need this, but its more comfy to decode */
/*
* This isn't needed, and can't actually capture the contents of
* the tuple accurately (because t_len isn't guaranteed to be big
* enough to contain old tuples which can be up to 1 GB long). But
* previous versions of 9.4 used this, so we can't change the WAL
* format.
*/
xlhdr_idx.header.t_infomask2 = old_key_tuple->t_data->t_infomask2;
xlhdr_idx.header.t_infomask = old_key_tuple->t_data->t_infomask;
xlhdr_idx.header.t_hoff = old_key_tuple->t_data->t_hoff;

19
src/backend/replication/logical/decode.c
View File

@ -653,6 +653,7 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
xl_heap_update *xlrec;
ReorderBufferChange *change;
char *data;
size_t remlen = r->xl_len;
xlrec = (xl_heap_update *) buf->record_data;
@ -666,6 +667,7 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
/* caution, remaining data in record is not aligned */
data = buf->record_data + SizeOfHeapUpdate;
remlen -= SizeOfHeapUpdate;
if (xlrec->flags & XLOG_HEAP_CONTAINS_NEW_TUPLE)
{
@ -677,6 +679,7 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
memcpy(&xlhdr, data, sizeof(xlhdr));
data += offsetof(xl_heap_header_len, header);
remlen -= offsetof(xl_heap_header_len, header);
datalen = xlhdr.t_len + SizeOfHeapHeader;
tuplelen = xlhdr.t_len;
@ -687,8 +690,10 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
DecodeXLogTuple(data, datalen, change->data.tp.newtuple);
/* skip over the rest of the tuple header */
data += SizeOfHeapHeader;
remlen -= SizeOfHeapHeader;
/* skip over the tuple data */
data += xlhdr.t_len;
remlen -= xlhdr.t_len;
}
if (xlrec->flags & XLOG_HEAP_CONTAINS_OLD)
@ -699,10 +704,17 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
memcpy(&xlhdr, data, sizeof(xlhdr));
data += offsetof(xl_heap_header_len, header);
remlen -= offsetof(xl_heap_header_len, header);
/* t_len is inconsistent with other cases, see log_heap_update */
tuplelen = xlhdr.t_len - offsetof(HeapTupleHeaderData, t_bits);
datalen = tuplelen + SizeOfHeapHeader;
/*
* NB: Even though xl_heap_header_len contains the tuple's length,
* it's length field is not wide enough. Use the whole record length
* minus the new tuple's length instead. We can't remove the record
* length from the WAL record format in 9.4 due to compatibility
* concerns - later versions don't have it anyway.
*/
datalen = remlen;
tuplelen = datalen - SizeOfHeapHeader;
change->data.tp.oldtuple =
ReorderBufferGetTupleBuf(ctx->reorder, tuplelen);
@ -710,6 +722,7 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
DecodeXLogTuple(data, datalen, change->data.tp.oldtuple);
#ifdef NOT_USED
data += datalen;
remlen -= datalen;
#endif
}