Re: [HACKERS] Custom compression methods

Hi,

I ran into another issue - after inserting some data into a table with a
tsvector column (without any compression defined), I can no longer read
the data.

This is what I get in the console:

db=# select max(md5(body_tsvector::text)) from messages;
ERROR: cache lookup failed for compression options 6432

and the stack trace looks like this:

Breakpoint 1, get_cached_compression_options (cmoptoid=6432) at
tuptoaster.c:2563
2563 elog(ERROR, "cache lookup failed for compression options %u",
cmoptoid);
(gdb) bt
#0 get_cached_compression_options (cmoptoid=6432) at tuptoaster.c:2563
#1 0x00000000004bf3da in toast_decompress_datum (attr=0x2b44148) at
tuptoaster.c:2390
#2 0x00000000004c0c1e in heap_tuple_untoast_attr (attr=0x2b44148) at
tuptoaster.c:225
#3 0x000000000083f976 in pg_detoast_datum (datum=<optimized out>) at
fmgr.c:1829
#4 0x00000000008072de in tsvectorout (fcinfo=0x2b41e00) at tsvector.c:315
#5 0x00000000005fae00 in ExecInterpExpr (state=0x2b414b8,
econtext=0x2b25ab0, isnull=<optimized out>) at execExprInterp.c:1131
#6 0x000000000060bdf4 in ExecEvalExprSwitchContext
(isNull=0x7fffffe9bd37 "", econtext=0x2b25ab0, state=0x2b414b8) at
../../../src/include/executor/executor.h:299

It seems the VARATT_IS_CUSTOM_COMPRESSED incorrectly identifies the
value as custom-compressed for some reason.

Not sure why, but the tsvector column is populated by a trigger that
simply does

NEW.body_tsvector
:= to_tsvector('english', strip_replies(NEW.body_plain));

If needed, the complete tool is here:

https://bitbucket.org/tvondra/archie

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services