maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxxx>]

Hi, Roberto!

On May 24, Roberto Spadim wrote:
> Hi guys i'm reading query cache code, and i have some doubts...
> mariadb-10.0.1 source:
> 
> 1)PROTOCOL_LOCAL:
> at line: 1412 (Query_cache::store_query)
> we have this comment:
> /* PROTOCOL_LOCAL results are not cached. */
> 
> what's PROTOCOL_LOCAL ? it's the unix socket? windows pipe? embedded?
> memcache? mysql? another thing like this? or it's the internal mariadb
> source running queries?

It's not used. Dead code.

> 2)the query_size=0 (MDEV-4516)
> i was reading at line 1680
> 
>   if (is_disabled() || thd->locked_tables_mode ||
> thd->variables.query_cache_type == 0)
>     goto err;
> 
> and line : 1694
> DBUG_ASSERT(query_cache_size != 0);           // otherwise cache would be
> disabled
> 
> why it's isn't used in query_cache_information plugin?
> *check that in line 1680 it test the "query_cache_type" too, *
> *in MDEV-4516 report about size=0 we didn't tested this case!!!*

query_cache_information plugin uses qc->is_disabled()
this should cover all cases.

> 3) i was at line 1886:
>   DBUG_PRINT("qcache", ("\
> long %d, 4.1: %d, bin_proto: %d, more results %d, pkt_nr: %d, \
> CS client: %u, CS result: %u, CS conn: %u, limit: %lu, TZ: 0x%lx, \
> sql mode: 0x%llx, sort len: %lu, conncat len: %lu, div_precision: %lu, \
> def_week_frmt: %lu, in_trans: %d, autocommit: %d",
> 
> is this the "primary key" of the query cache!?!?!?!?!?!?!
> could we use a sha1 or another "primary key" method (index [] of the query
> in cache + '';'+ 5 bytes of a hash key to compare if the index still with
> the same query)
> to easly show query entry "number", and allow a "delete from
> query_cache_information where key=xxx" function?
> 
> at line 1938 we have this maybe the query position on cache ("primary key
> of query cache")?:
> DBUG_PRINT("qcache", ("Query have result 0x%lx", (ulong) query));

No, information_schema tables are read-only.


Regards,
Sergei