Re: toast tables

On Mon, May 9, 2016 at 6:59 PM, drum(dot)lucas(at)gmail(dot)com <drum(dot)lucas(at)gmail(dot)com>
wrote:

> Hi all,
>
> I'm currently using PostgreSQL 9.2 and my DB size is 2.2 TB..
>
> Running the query below;
>
> WITH schema_size AS (
>> SELECT
>> tab.table_catalog AS database_name,
>> tab.table_schema AS schema_name,
>> tab.table_name,
>> pg_total_relation_size(table_schema || '.' || tab.table_name) AS
>> table_size_total,
>> pg_relation_size(table_schema || '.' || tab.table_name) AS table_size
>> FROM information_schema.tables tab
>> WHERE table_schema NOT IN ('pg_catalog', 'information_schema')
>> ), pretty_size AS (
>> SELECT
>> database_name,
>> schema_name,
>> pg_database_size(database_name) AS database_size_bigint,
>> pg_size_pretty(pg_database_size(database_name)) AS database_size,
>> sum(table_size_total) AS schema_size_bigint_total,
>> pg_size_pretty(sum(table_size_total)) AS schema_size_total,
>> sum(table_size) AS schema_size_bigint,
>> pg_size_pretty(sum(table_size)) AS schema_size
>> FROM schema_size
>> GROUP BY database_name, schema_name
>> )
>> SELECT
>> database_name,
>> schema_name,
>> database_size,
>> schema_size_total,
>> schema_size,
>> ((schema_size_bigint_total * 100) / database_size_bigint) AS perc_total,
>> ((schema_size_bigint * 100) / database_size_bigint) AS perc
>> FROM pretty_size
>
>
> I get the following data:
>
> *schema | schema_size_total | schema_size | perc_total | perc*
>
> gorfs | 1824 GB | 20 GB | 85.4308477608319514 | 0.94562882033477939710
>
>
> As you can see, the GORFS schema is 1.8 TB.
> That is all pg_Toast tables....
>
> I read the documentation [1] but actually I couldn't understand:
>
>
> Is there any way to get the size decreased ?
>
> The DB is in production, so I can't run the VACCUM FULL.
> Is there anything I can do?
>
> Is the pg_toast normal?
>

TOAST (The Oversized Attribute Storage Technique) is completely normal and
automatic based on your datatypes.

Have you tried to estimate bloat?

(from https://github.com/ioguix/pgsql-bloat-estimation/tree/master/table)

/* WARNING: executed with a non-superuser role, the query inspect only
tables you are granted to read.
* This query is compatible with PostgreSQL 9.0 and more
*/
SELECT current_database(), schemaname, tblname, bs*tblpages AS real_size,
(tblpages-est_tblpages)*bs AS extra_size,
CASE WHEN tblpages - est_tblpages > 0
THEN 100 * (tblpages - est_tblpages)/tblpages::float
ELSE 0
END AS extra_ratio, fillfactor, (tblpages-est_tblpages_ff)*bs AS
bloat_size,
CASE WHEN tblpages - est_tblpages_ff > 0
THEN 100 * (tblpages - est_tblpages_ff)/tblpages::float
ELSE 0
END AS bloat_ratio, is_na
-- , (pst).free_percent + (pst).dead_tuple_percent AS real_frag
FROM (
SELECT ceil( reltuples / ( (bs-page_hdr)/tpl_size ) ) + ceil( toasttuples
/ 4 ) AS est_tblpages,
ceil( reltuples / ( (bs-page_hdr)*fillfactor/(tpl_size*100) ) ) + ceil(
toasttuples / 4 ) AS est_tblpages_ff,
tblpages, fillfactor, bs, tblid, schemaname, tblname, heappages,
toastpages, is_na
-- , stattuple.pgstattuple(tblid) AS pst
FROM (
SELECT
( 4 + tpl_hdr_size + tpl_data_size + (2*ma)
- CASE WHEN tpl_hdr_size%ma = 0 THEN ma ELSE tpl_hdr_size%ma END
- CASE WHEN ceil(tpl_data_size)::int%ma = 0 THEN ma ELSE
ceil(tpl_data_size)::int%ma END
) AS tpl_size, bs - page_hdr AS size_per_block, (heappages +
toastpages) AS tblpages, heappages,
toastpages, reltuples, toasttuples, bs, page_hdr, tblid, schemaname,
tblname, fillfactor, is_na
FROM (
SELECT
tbl.oid AS tblid, ns.nspname AS schemaname, tbl.relname AS tblname,
tbl.reltuples,
tbl.relpages AS heappages, coalesce(toast.relpages, 0) AS
toastpages,
coalesce(toast.reltuples, 0) AS toasttuples,
coalesce(substring(
array_to_string(tbl.reloptions, ' ')
FROM '%fillfactor=#"__#"%' FOR '#')::smallint, 100) AS fillfactor,
current_setting('block_size')::numeric AS bs,
CASE WHEN version()~'mingw32' OR
version()~'64-bit|x86_64|ppc64|ia64|amd64' THEN 8 ELSE 4 END AS ma,
24 AS page_hdr,
23 + CASE WHEN MAX(coalesce(null_frac,0)) > 0 THEN ( 7 + count(*) )
/ 8 ELSE 0::int END
+ CASE WHEN tbl.relhasoids THEN 4 ELSE 0 END AS tpl_hdr_size,
sum( (1-coalesce(s.null_frac, 0)) * coalesce(s.avg_width, 1024) )
AS tpl_data_size,
bool_or(att.atttypid = 'pg_catalog.name'::regtype) AS is_na
FROM pg_attribute AS att
JOIN pg_class AS tbl ON att.attrelid = tbl.oid
JOIN pg_namespace AS ns ON ns.oid = tbl.relnamespace
JOIN pg_stats AS s ON s.schemaname=ns.nspname
AND s.tablename = tbl.relname AND s.inherited=false AND
s.attname=att.attname
LEFT JOIN pg_class AS toast ON tbl.reltoastrelid = toast.oid
WHERE att.attnum > 0 AND NOT att.attisdropped
AND tbl.relkind = 'r'
GROUP BY 1,2,3,4,5,6,7,8,9,10, tbl.relhasoids
ORDER BY 2,3
) AS s
) AS s2
) AS s3
-- WHERE NOT is_na
-- AND tblpages*((pst).free_percent +
(pst).dead_tuple_percent)::float4/100 >= 1

--
Scott Mead
Sr. Architect
OpenSCG
http://openscg.com

> [1] - http://www.postgresql.org/docs/9.2/static/storage-toast.html
>
> Thanks
> Lucas
>