Re: experimental pg_qcache patch

On Sun, Apr 14, 2002 at 10:13:17PM +0200, Karel Zak wrote:

> > (2) Sometimes executing a PREPARE gives this warning:
> >
> > nconway=> prepare q1 as select * from pg_class;
> > WARNING: AllocSetFree: detected write past chunk end in TransactionCommandContext 0x83087ac
> > PREPARE
> >
> > Does anyone know what problem this indicates?
>
> The memory managment is diffrent between 7.0 and 7.2. There is
> needful port cache shared-memory managment. I will look at it.

Hmm, I probably found it be first look to patch file.

The WARNING message is from leak detection. I'm sure that you see
this message if you use SHARE cache type.

- PREPARE_KEY_PREFIX_SIZE is 4 not 3

- in the PrepareKey() is needful fix:

+ if (store == PREPARE_STORE_SHARE) { /* shared between same DB */
+ *flag |= QCF_SHARE_NOTREMOVEABLE;
+ key = (char *) palloc(strlen(name) + PREPARE_KEY_PREFIX_SIZE
+ + strlen(DatabaseName) +1);
^^^^^^^
must be 3

+ sprintf(key, "%s_%s_", DatabaseName, PREPARE_KEY_PREFIX);
^^^^^^
the space for '_' is not allocated :-(

It's my bug probably, I good knew why we need leak detection :-)

Karel

PS. Sorry that I don't send a patch, but now I haven't my computer there.
--
Karel Zak <zakkr(at)zf(dot)jcu(dot)cz>
http://home.zf.jcu.cz/~zakkr/

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