Request to help on GIS Query improvement suggestion.

From: postggen2020 s <postggen2020(at)gmail(dot)com>
To: pgsql-admin(at)postgresql(dot)org, pgsql-general(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
Subject: Request to help on GIS Query improvement suggestion.
Date: 2020-05-22 10:53:16
Message-ID: CAJ=omAh-1aZcDxnAzgNKXde2qzw9Jt+GQBL0xM8ac1=wFfTbEg@mail.gmail.com
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Hi Team,

Thanks for your support.

Could someone please suggest on the below query.

One of the query which was created on GIS data is taking a long time and
even it is not taking the index as well. I have included all the required
details for reference.

Database Stack:
===============
PostgreSQL : 9.5.15
Postgis: 2.2.7

Table Structure:
===================

ALTER TABLE SCHEMA.TABLE_NAME ADD COLUMN parental_path text;

Created Indexes on column parental_path:
=================================

CREATE INDEX cable_pair_parental_path_idx
ON SCHEMA.TABLE_NAME
USING btree
(md5(parental_path) COLLATE pg_catalog."default");

CREATE INDEX cable_pair_parental_path_idx_fulltext
ON SCHEMA.TABLE_NAME
USING gist
(parental_path COLLATE pg_catalog."default");

Sample data in "parental_path" column:
======================================

'route--2309421/2951584/3373649/2511322/1915187/2696397/2623291/2420708/2144348/2294454,circuit--88458/88460,sheath--8874'

Actual Query:
=============

SELECT seq_no + 1 FROM SCHEMA.TABLE_NAME WHERE (parental_path LIKE
'%,sheath--' || cable_seq_id || ',%' OR parental_path LIKE 'sheath--' ||
cable_seq_id || ',%' OR parental_path LIKE '%,sheath--' || cable_seq_id OR
parental_path = 'sheath--' || cable_seq_id) ORDER BY seq_no DESC LIMIT 1;

Explain Plan:
=============

Limit (cost=108111.60..108111.61 rows=1 width=4) (actual
time=4597.605..4597.605 rows=0 loops=1)
Output: ((seq_no + 1)), seq_no
Buffers: shared hit=2967 read=69606 dirtied=1
-> Sort (cost=108111.60..108113.09 rows=595 width=4) (actual
time=4597.603..4597.603 rows=0 loops=1)
Output: ((seq_no + 1)), seq_no
Sort Key: TABLE_NAME.seq_no DESC
Sort Method: quicksort Memory: 25kB
Buffers: shared hit=2967 read=69606 dirtied=1
-> *Seq Scan on SCHEMA.TABLE_NAME (cost=0.00..108108.63 rows=595
width=4) (actual time=4597.595..4597.595 rows=0 loops=1)*
Output: (seq_no + 1), seq_no
Filter: ((TABLE_NAME.parental_path ~~
'%,sheath--64690,%'::text) OR (TABLE_NAME.parental_path ~~
'sheath--64690,%'::text) OR (TABLE_NAME.parental_path ~~
'%,sheath--64690'::text) OR (TABLE_NAME.parental_path =
'sheath--64690'::text))
Rows Removed by Filter: 1930188
Buffers: shared hit=2967 read=69606 dirtied=1

Please share your suggestion if I have to change or add new objects to the
table etc..

Thanks & Regards,
PostgAnn.

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