PG_CLASS_INFO is an Amazon Redshift system view built on the PostgreSQL catalog tables PG_CLASS and PG_CLASS_EXTENDED. PG_CLASS_INFO includes details about table creation time and the current distribution style. For more information, see Data distribution for query optimization.
PG_CLASS_INFO is visible to all users. Superusers can see all rows; regular users can see only their own data. For more information, see Visibility of data in system tables and views.
Table columns
PG_CLASS_INFO shows the following columns in addition to the columns in
PG_CLASS. The oid column in PG_CLASS is called reloid in the PG_CLASS_INFO table.
| Column name | Data type | Description |
|---|---|---|
| relcreationtime | timestamp | Time in UTC that the table was created. |
| releffectivediststyle | integer | The distribution style of a table or, if the table uses automatic distribution, the current distribution style assigned by Amazon Redshift. |
The RELEFFECTIVEDISTSTYLE column in PG_CLASS_INFO indicates the current distribution style for the table. If the table uses automatic distribution, RELEFFECTIVEDISTSTYLE is 10, 11, or 12, which indicates whether the effective distribution style is AUTO (ALL), AUTO (EVEN), or AUTO (KEY). If the table uses automatic distribution, the distribution style might initially show AUTO (ALL), then change to AUTO (EVEN) when the table grows or AUTO (KEY) if a column is found to be useful as a distribution key.
The following table gives the distribution style for each value in RELEFFECTIVEDISTSTYLE column:
| RELEFFECTIVEDISTSTYLE | Current distribution style |
|---|---|
| 0 | EVEN |
| 1 | KEY |
| 8 | ALL |
| 10 | AUTO (ALL) |
| 11 | AUTO (EVEN) |
| 12 | AUTO (KEY) |
Example
The following query returns the current distribution style of tables in the catalog.
select reloid as tableid,trim(nspname) as schemaname,trim(relname) as tablename,reldiststyle,releffectivediststyle,
CASE WHEN "reldiststyle" = 0 THEN 'EVEN'::text
WHEN "reldiststyle" = 1 THEN 'KEY'::text
WHEN "reldiststyle" = 8 THEN 'ALL'::text
WHEN "releffectivediststyle" = 10 THEN 'AUTO(ALL)'::text
WHEN "releffectivediststyle" = 11 THEN 'AUTO(EVEN)'::text
WHEN "releffectivediststyle" = 12 THEN 'AUTO(KEY)'::text ELSE '<<UNKNOWN>>'::text END as diststyle,relcreationtime
from pg_class_info a left join pg_namespace b on a.relnamespace=b.oid;
tableid | schemaname | tablename | reldiststyle | releffectivediststyle | diststyle | relcreationtime
---------+------------+-----------+--------------+-----------------------+------------+----------------------------
3638033 | public | customer | 0 | 0 | EVEN | 2019-06-13 15:02:50.666718
3638037 | public | sales | 1 | 1 | KEY | 2019-06-13 15:03:29.595007
3638035 | public | lineitem | 8 | 8 | ALL | 2019-06-13 15:03:01.378538
3638039 | public | product | 9 | 10 | AUTO(ALL) | 2019-06-13 15:03:42.691611
3638041 | public | shipping | 9 | 11 | AUTO(EVEN) | 2019-06-13 15:03:53.69192
3638043 | public | support | 9 | 12 | AUTO(KEY) | 2019-06-13 15:03:59.120695
(6 rows)
