Re: How to detect if a postgresql gin index is bloated

The pgstattuple function provides the following useful columns:

- table_len: The length of the table.
- tuple_count: The number of tuples.
- tuple_len: The length of the tuples.
- dead_tuple_count: The number of dead tuples.
- dead_tuple_len: The length of dead tuples.
- free_space: The amount of free space.

Example

How you might use this function:

SELECT * FROM pgstattuple('gin_index_name');

Interpreting Results

- If the dead_tuple_count is high relative to the tuple_count, this
indicates bloat.
- If free_space is a significant portion of table_len, the index may be
bloated.

Using pg_trgm for Trigram Indexes

If you're using a GIN index with the pg_trgm extension (for trigram
indexes), you might also consider analyzing the table and index sizes
directly:

SELECT
pg_size_pretty(pg_relation_size('table_name')) AS table_size,
pg_size_pretty(pg_total_relation_size('table_name')) AS total_size,
pg_size_pretty(pg_relation_size('gin_index_name')) AS index_size;

Vacuum and Reindex

If you determine that your GIN index is bloated, you can use VACUUM and
REINDEX to reclaim space:

VACUUM ANALYZE your_table_name;
REINDEX INDEX your_gin_index_name;

By following these steps, you should be able to detect and address bloat in
your PostgreSQL GIN indexes effectively.

On Fri, Jul 26, 2024 at 8:01 AM Keith Fiske <keith(dot)fiske(at)crunchydata(dot)com>
wrote:

>
>
> On Thu, Jul 25, 2024 at 8:59 AM khan Affan <bawag773(at)gmail(dot)com> wrote:
>
>> Hello Kam Fook
>> You can use pgstattuple extension, & you can use pg_trgm or
>> gin_index_stats functions from the pgstattuple extension to check for bloat
>> in GIN indexes.
>> Thank & Regards
>>
>> *Muhammad Affan (*아판*)*
>>
>> *PostgreSQL Technical Support Engineer** / Pakistan R&D*
>>
>> On Thu, Jul 25, 2024 at 2:07 AM Wong, Kam Fook (TR Technology) <
>> kamfook(dot)wong(at)thomsonreuters(dot)com> wrote:
>>
>>> I have a GIN index. Is there a way to detect if a postgres GIN index is
>>> bloated or not? The regular select * from pgstatindex(‘indexname’); does
>>> not work because the GIN index is not btree index.
>>>
>>>
>>>
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>>
>
> Any more insight on how to use those two options to actually calculate GIN
> bloat? From what I could tell pgstattuple didn't provide anything that
> could be used. I hadn't looked further into the other yet, but if you know
> how to do that already that info would be great.
>
> --
> Keith Fiske
> Senior Database Engineer
> Crunchy Data - http://crunchydata.com
>