index unique - Mailing list pgsql-general

From Marc Millas
Subject index unique
Date
Msg-id CADX_1aYbmMHK4wqHd=p_fGsNMOgEB7oe0BY_9ZTWv3e-TQx+oA@mail.gmail.com
Whole thread Raw
Responses Re: index unique  (Paul Ramsey <pramsey@cleverelephant.ca>)
Re: index unique  ("Peter J. Holzer" <hjp-pgsql@hjp.at>)
Re: index unique  (Thomas Kellerer <shammat@gmx.net>)
List pgsql-general
Hi,
postgres 12 with postgis.
on a table we need a primary key and to get a unique combinaison, we need 3 columns of that table:
1 of type integer,
1 of type text,
1 of type geometry

creating the PK constraint doesn work: (even with our current small data set)
ERROR:  index row size 6072 exceeds btree version 4 maximum 2704 for index "xxx_spkey"
DETAIL:  Index row references tuple (32,1) in relation "xxx".
HINT:  Values larger than 1/3 of a buffer page cannot be indexed.
Consider a function index of an MD5 hash of the value, or use full text indexing.


ok. we can do this.
but if so, we need to create a gist index on the geometry column to do any topology request.
so 2 indexes containing this single column.

if we install extension btree_gist, no pb to create an index on all 3 columns.
but as gist does not support unicity, this index cannot be used for the PK.

OK, we may try to use a function to get the bounding box around the geometry objects and use the result into a btree index........

Any idea (I mean: another idea !) to tackle this ?
Or any critic on the "solution" ??

thanks,


Marc MILLAS
Senior Architect
+33607850334

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