Re: Insert only table and size of GIN index JSONB field.

On Tue, May 3, 2016 at 1:35 PM, Maxim Boguk <maxim(dot)boguk(at)gmail(dot)com> wrote:

>
>
> On Tue, May 3, 2016 at 8:09 PM, Maxim Boguk <maxim(dot)boguk(at)gmail(dot)com> wrote:
>
>> Hi,
>>
>> I started with empty table with index over
>> custom_fields | jsonb
>> field
>> defined as:
>> "idx_learners_custom_fields" gin (custom_fields)
>> Globally gin_pending_list_limit set to 2MB.
>> Database version is 9.5.2.
>>
>> Now question:
>> If table populated with 1M records in single transaction then the final
>> size of the GIN index is:
>> 4265 MB
>> but after I performed reindex index idx_learners_custom_fields;
>> the index size had been reduced 15x to 295 MB.
>>
>> Is this behavior expected?
>>
>
> It's look easy to reproduce.
> I can send a sample dataset for analyze.
>

sample data are always welcome !

>
> drop table if exists test;
> create table test (custom_fields jsonb);
> create index test_gin_key on test USING GIN(custom_fields);
> insert into test select custom_fields from public.learners;
> INSERT 0 1000000
> \di+ test_gin_key
> List of relations
> Schema | Name | Type | Owner | Table | Size | Description
> --------+--------------+-------+----------+-------+---------+-------------
> public | test_gin_key | index | postgres | test | 4211 MB |
>
> reindex index test_gin_key;
>
> \di+ test_gin_key
> List of relations
> Schema | Name | Type | Owner | Table | Size | Description
> --------+--------------+-------+----------+-------+--------+-------------
> public | test_gin_key | index | postgres | test | 295 MB |
>
>
> ​
>
>
> --
> Maxim Boguk
> Senior Postgresql DBA
> http://www.postgresql-consulting.com/
>
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>
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>