Heikki Linnakangas wrote:
> Dave Page wrote:
>> REINDEX is similar to a drop and recreate of the index in that the index
>> contents are rebuilt from scratch. However, the locking considerations
>> are rather different. REINDEX locks out writes but not reads of the
>> index's parent table. It also takes an exclusive lock on the specific
>> index being processed, which will block reads that attempt to use that
>> index. In contrast, DROP INDEX momentarily takes exclusive lock on the
>> parent table, blocking both writes and reads. The subsequent CREATE
>> INDEX locks out writes but not reads; since the index is not there, no
>> read will attempt to use it, meaning that there will be no blocking but
>> reads may be forced into expensive sequential scans. Another important
>> point is that the drop/create approach invalidates any cached query
>> plans that use the index, while REINDEX does not.
>
> So the advantage is that drop+create will allow all reads to run
> concurrently, though they might have to use sequential scans. Hmm, I
> wonder if a CREATE+DROP+rename would be even better. Could use
> CONCURRENT-mode in the create as well to allow concurrent writes...
Would be even nicer to include in the server... maybe REINDEX
CONCURRENTLY...
> I know I know, no new features at this point :).
Indeed :-)
/D