How does Index scan perform a scan for overlapping Index Cond ?
If I get a plan like this, what will actually be performed if EXPLAIN
shows this:
Sort (cost=12.90..12.91 rows=1 width=207) Sort Key: log_actionseq -> Index Scan using sl_log_1_idx2_hu,
sl_log_1_idx2_hu,
sl_log_1_idx2_hu, sl_log_1_idx2_hu on sl_log_1 (cost=0.00..12.89 rows=1
width=207) Index Cond: ( ((log_xid < '1349053093') AND (log_xid >= '1349052761'))
OR ((log_xid < '1349053093') AND (log_xid >= '1349052761'))
OR ((log_xid < '1349053093') AND (log_xid >= '1349052761'))
OR ((log_xid < '1349053093') AND (log_xid >= '1349052761')) )
(this is from a query generated by Slony for 4 sets replicated from the
same master)
Will the same range be scanned 4 times ?
Or is the scan method smart enough to collapse them into one pass ?
Or does this actually mean 4 conactenated index scans (Index Scan using
X, X, X, X on sl_log_1) ?
--
Hannu Krosing <hannu@skype.net>
