I think I've found something of interest.
When I create a new table, the plan for it believes that the table
contains 2 rows, not 0. Also, since the engine knows when we run an
insert, and also knows how many rows a delete nukes, wouldn't it be better
to update the stats after every select and delete?
-Michael
equipment=> CREATE TABLE xuserid(
equipment-> oldid varchar(12),
equipment-> newid int4,
equipment-> PRIMARY KEY (oldid,newid)
equipment-> );
NOTICE: CREATE TABLE/PRIMARY KEY will create implicit index
'xuserid_pkey' for table 'xuserid'
CREATE
equipment=> \d xuserid_pkey
Table = xuserid_pkey
+----------------------------------+----------------------------------+-------+
| Field | Type |
Length|
+----------------------------------+----------------------------------+-------+
| oldid | varchar() |
12 |
| newid | int4 |
4 |
+----------------------------------+----------------------------------+-------+
equipment=> explain select * from xuserid where newid=859;
NOTICE: QUERY PLAN:
Seq Scan on xuserid (cost=43.00 rows=2 width=16)
EXPLAIN
equipment=> vacuum analyze;
VACUUM
equipment=> explain select * from xuserid where newid=859;
NOTICE: QUERY PLAN:
Seq Scan on xuserid (cost=0.00 rows=0 width=16)
EXPLAIN
