Re: Lack of index usage when doing array casts - Mailing list pgsql-performance

From Tom Lane
Subject Re: Lack of index usage when doing array casts
Date
Msg-id 5576.1393009497@sss.pgh.pa.us
Whole thread Raw
In response to Lack of index usage when doing array casts  (Alexey Klyukin <alexk@hintbits.com>)
Responses Re: Lack of index usage when doing array casts  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-performance
Alexey Klyukin <alexk@hintbits.com> writes:
> We had a problem with PostgreSQL not using an index scan in 2 similar
> queries, the only difference between them is the array cast from text[] to
> location_type[] (array of enum values).

Hmm.  IIRC the text to enum cast is considered stable not immutable, which
is why that doesn't get folded to a Const on sight.  However, it seems
like it'd be okay for scalararraysel() to reduce stable expressions for
estimation purposes, ie it should be using estimate_expression_value.

            regards, tom lane


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