On 09/09/2016 03:41 PM, Tom Lane wrote: > Satoshi Nagayasu <sn...@uptime.jp> writes: >> According to the manual, running REINDEX does not take any locks >> on the parent table which block read operations. >> Actually, REINDEX blocks SELECT queries, maybe in the planning phase. > > Hm. REINDEX does take out only ShareLock on the table, which would not > block DML, but it takes out AccessExclusiveLock on the index. That > blocks the planner's attempts to acquire information about the table's > indexes. > > In the case of an update query I think there's little we can do about > this; the executor would have to update the index anyway. For a pure > SELECT, you could imagine having the planner do a conditional lock acquire > and ignore the index if that fails. Would that be better than blocking? > Not sure. You could end up with a really bad plan if the index was > critical for efficient processing of the query.
I agree, things could get awful without certain indexes (I'm thinking of partial indexes in particular). Also, the very next sentence after the one cited says that a SELECT will block if it tries to use the index in question, so I'm not even sure there's anything at all to do here. -- Vik Fearing +33 6 46 75 15 36 http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support -- Sent via pgsql-docs mailing list (pgsql-docs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-docs
