Обсуждение: [GENERAL] Multicolumn Index on OR conditions
Hi, within a query with two or more conditions with "OR", example: "where a = 2 or b < 3" could be useful to speed up the query a multi-column index (a,b) even though the two conditions are in "OR" and not in "AND"? Thank you! F -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
On 2017-09-19 10:08, Job wrote: > Hi, > > within a query with two or more conditions with "OR", example: > > "where a = 2 or b < 3" > > could be useful to speed up the query a multi-column index (a,b) even > though the two conditions are in "OR" and not in "AND"? > > Thank you! > F Having any kind of index usually better than none because it may prevent a seqscan, but an OR probably works faster if you have a separate index on B. But, EXPLAIN can show you what the database actually does, and give some indication of why it thinks it should do it that way. regards, Vincent. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
No You should try with 2 single column indexes and may be rewrite your query with a Union All syntax -- Sent from: http://www.postgresql-archive.org/PostgreSQL-general-f1843780.html -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general