Re: SELECT with LIKE clause makes full table scan - Mailing list pgsql-general

Hello,

We face in a PostgreSQL 11.4 installation on a potent Linux host a
serious performance degree.

A SELECT with a LIKE clause on a table with ca. 5.200.000 rows on a
column with an Index ignores this and does a full table scan:

sisis=# explain (analyze, buffers) select * from d01buch where d01ort like 'Z 9610%' ;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------
Gather (cost=1000.00..680262.71 rows=510 width=952) (actual time=1324.096..1349.429 rows=1 loops=1)
Workers Planned: 4
Workers Launched: 4
Buffers: shared hit=102040 read=560674
-> Parallel Seq Scan on d01buch (cost=0.00..679211.71 rows=128 width=952) (actual time=1117.663..1315.062 rows=0 loops=5)
Filter: (d01ort ~~ 'Z 9610%'::text)
Rows Removed by Filter: 1055853
Buffers: shared hit=102040 read=560674
Planning Time: 2.028 ms
Execution Time: 1349.593 ms
(10 Zeilen)

Why is this (ignoring the Index) and what could be done?

Thanks

        matthias


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Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
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