From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mike Martin <redtux1@gmail.com>
cc: pgsql-sql <pgsql-sql@lists.postgresql.org>
Subject: Re: Weird issue with truncation of values in array with some tables
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Comments: In-reply-to Mike Martin <redtux1@gmail.com>
	message dated "Sun, 16 Aug 2020 14:48:16 +0100"
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Date: Sun, 16 Aug 2020 13:12:50 -0400
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Mike Martin <redtux1@gmail.com> writes:
> I have come across a weird issue with truncation of text in an array (in
> this case using pg_indexes view)
> This query truncates the second array element at 63 characters
> SELECT ARRAY[indexname,indexdef] FROM pg_indexes
> However reversing the order doesn't truncate
> SELECT ARRAY[indexdef,indexname] FROM pg_indexes
> Anyone know why this behaviour occurs?

indexname is of type name, indexdef is of type text, and the rules
for inferring the type of an array[] construct are such that the
first element's type wins in these cases.

regression=3D# SELECT pg_typeof(ARRAY[indexname,indexdef]) FROM pg_indexes=
 limit 1;
 pg_typeof =

-----------
 name[]
(1 row)

regression=3D# SELECT pg_typeof(ARRAY[indexdef,indexname]) FROM pg_indexes=
 limit 1;
 pg_typeof =

-----------
 text[]
(1 row)

You could insert an explicit cast to text to avoid the truncation
of indexdef to name:

regression=3D# SELECT pg_typeof(ARRAY[indexname::text,indexdef]) FROM pg_i=
ndexes limit 1;
 pg_typeof =

-----------
 text[]
(1 row)

The documentation about that is here:
https://www.postgresql.org/docs/current/typeconv-union-case.html
although looking at this example it seems like that description isn't
telling the full truth.

			regards, tom lane