Re: List of table names of a DB

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
mastersproject. In order to this, I need to store details(like name) of each table the query uses. In essence, I need
tostore 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
gargantuantask 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'tbe 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: dgrowleyml@gmail.com
>> To: in.live.in@live.in
>> CC: pgsql-hackers@postgresql.org
>>
>> On 8 January 2015 at 22:41, Deepak S <in.live.in@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.
Myplan 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
thateach 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:
explainselect * 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-general@postgresql.org list.
>> Regards
>> David Rowley                                                    
>
>