On 04/22/2014 04:58 PM, AI Rumman wrote:
Hi,

Is it good to have toast table for information schema table? I am using
Postgresql 8.4 and current state is:

*select datname, datfrozenxid from pg_database; *
   datname  | datfrozenxid
-----------+--------------
  template1 |   1462730397
  template0 |   1462741467
  postgres  |   1562754912
  jangles   |   1459615432
(4 rows)
*
*
*
*
*select * from pg_class  where relfrozenxid  = 1459615432;*
     relname     | reltoastidxid | relhasindex | relfrozenxid
----------------+---------------+-------------+--------------
  pg_toast_11447 |         11451 | t           |   1459615432
(1 row)
*
*
*
*
*select 11447::regclass; *
             regclass
---------------------------------
  information_schema.sql_features
(1 row)

Please advice.

A TOAST table is used whenever the actual table has variable length fields that meet certain criteria:

http://www.postgresql.org/docs/9.3/static/storage-toast.html

information_schema.sql_features schema is:

test=# \d information_schema.sql_features
             Table "information_schema.sql_features"
      Column      |               Type                | Modifiers
------------------+-----------------------------------+-----------
 feature_id       | information_schema.character_data |
 feature_name     | information_schema.character_data |
 sub_feature_id   | information_schema.character_data |
 sub_feature_name | information_schema.character_data |
 is_supported     | information_schema.yes_or_no      |
 is_verified_by   | information_schema.character_data |
 comments         | information_schema.character_data |

From here you see character_data is not fixed length:

http://www.postgresql.org/docs/9.3/static/infoschema-datatypes.html

so a TOAST table is not out of order.

I see it on my database also.


Thanks.


--
Adrian Klaver
adrian.kla...@aklaver.com


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