Re: creating gist index on ltree column failed

Thanks Tom for your reply. my pg version is 11.8.

I used "select into" to export some long rows to a new table, then tried to create gist index on it. I got same error as yours.
===
CREATE INDEX order_tree_path_idx_mytbl
ON mytbl USING gist
(path);
ERROR: index row size 7496 exceeds maximum 8152 for index "order_tree_path_idx_mytbl"
===

so it looks like the errors I got might be related with other data in the same table, but I am not sure which rows, there are 12k rows in the table.

regarding as the gist index size limitation 8152 , do you know how to workaround it? if we set the block size from 8k to a large value(32k), will it help?

thank you

James

________________________________
From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Sent: Wednesday, September 23, 2020 10:37
To: jian xu <jamesxu(at)outlook(dot)com>
Cc: pgsql-admin(at)lists(dot)postgresql(dot)org <pgsql-admin(at)lists(dot)postgresql(dot)org>
Subject: Re: creating gist index on ltree column failed

jian xu <jamesxu(at)outlook(dot)com> writes:
> I tried to create gist index on a ltree column, first I got error
> ERROR: stack depth limit exceeded

Hm. What PG version is this? If it's up-to-date, can you provide some
sample data that causes such problems?

> one thing I notice is, there are some rows with many levels(more than 1k levels) in the ltree, if I delete those rows, creating gist index works

I tried to reproduce this using just that information, but all I got was

regression=# create table t (f1 ltree);
CREATE TABLE
regression=# create index on t using gist(f1);
CREATE INDEX
regression=# insert into t select ('0.' || (select string_agg(g::text,'.') from generate_series(1,100) g))::ltree;
INSERT 0 1
regression=# insert into t select ('0.' || (select string_agg(g::text,'.') from generate_series(1,1000) g))::ltree;
ERROR: index row requires 16048 bytes, maximum size is 8191

which is perhaps an annoying limitation, but it's not a bug.

(I'm kind of wondering about the use-case for such long ltrees, anyway.)

regards, tom lane