Also see:
https://code.google.com/p/pqc/
A project to implement a query cache using pgpool code, probably lots of
good ideas there.
Cheers
Mark
On 09/01/15 19:38, Tatsuo Ishii wrote:
Hi,
pgpool-II (pgpool.net) does exactly the same thing.
It receive SELECT query from clients, 1) parse it to find table names,
and 2) gets the oids (unique identifier in the PostgreSQL system
catalog) to recognize them. when the SELECT succeeds , it store the
query result (cache) on either shared memory or memcached according to
user's choice. For query cache invalidation, pgpool-II remembers all
oids related to the SELECTs which are source of query cache. If one of
tables get updated, pgpoool-II invalidates all of cache using the oid.
For #1, pgpool-II has a query parser copied from PostgreSQL.
pgpool-II is an open source project, so you could get some idea to
implement your own tool.
Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp
Sorry, it's not about querying. I am implementing an invalidation mechanism for
Postgres Query Cache as part of my masters project. In order to this, I need to
store details(like name) of each table the query uses. In essence, I need to
store the table names of the cached queries.
Initially, I thought of writing a code that could extract the table names but
later discovered that it is a gargantuan task as I shall have to include around
600 production rules as was hinted in a Stackoverflow Exchange post. Hence, I
thought of getting hold of the data structure used for storing table names of a
DB but I couldn't get it.
Sorry for the long post but do you know where these tables information of a DB
gets stored? Or can you suggest me a mechanism(needn't be fully perfect) to
extract the table names? I went through the parser of postgres but it was
confusing.
Thanks
Date: Fri, 9 Jan 2015 00:46:30 +1300
Subject: Re: [HACKERS] List of table names of a DB
From: dgrowle...@gmail.com
To: in.live...@live.in
CC: pgsql-hackers@postgresql.org
On 8 January 2015 at 22:41, Deepak S <in.live...@live.in> wrote:
Hello, I am unable to find the function which retrieves the 'list of names of
the tables' used in a DB.
You may find what you want in: select table_name from information_schema.tables;
http://www.postgresql.org/docs/9.4/static/infoschema-tables.html
Reason: I need a mechanism by which I can extract the names of the tables
used in a query which has been parsed. My plan is to check for a match of each
word in the query with a list of names of the tables used in the current DB so
that each hit confirms a 'table name' in the query in most cases.
This sounds rather flaky.
Maybe it would be better to just EXPLAIN the query and see if you get error code
42P01postgres=# \set VERBOSITY verbosepostgres=# explain select * from
doesnotexist;ERROR: 42P01: relation "doesnotexist" does not existLINE 1:
explain select * from doesnotexist;
Unfortunately this won't help you much if you want to know all of the tables
that don't exist.
Also, just for the future, a question like this might be more suited for the
pgsql-gene...@postgresql.org list.
Regards
David Rowley
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