Loles <lolesft(at)gmail(dot)com> writes:
> We have seen performance down when we use WHERE UPPER(name) LIKE
> UPPER('%Alice%') in the condition.
> If we compare with WHERE UPPER(name) = UPPER('Alice') it runs very fast.
Presumably, that works well because you have a btree index on UPPER(name).
But btree can't optimize a pattern with a leading '%' --- see
https://www.postgresql.org/docs/current/indexes-types.html#INDEXES-TYPES-BTREE
You could possibly use a pg_trgm index instead, see
https://www.postgresql.org/docs/current/pgtrgm.html
The performance properties will be somewhat different from btree,
but it might get the job done.
regards, tom lane