Partitioned TEMP tables
I have an issue regarding partitioned TEMP tables.
I have a database with a number of families of tables partitioned by day as
described in section 5.10 of the User's Manual. I have an empty parent
tables each with a number of child tables containing data partitioned by
date. Each child has a CHECK condition on the date of the data. This works
fine when I execute a SELECT statement against the parent table and specify
a value for the date.
However, I am currently working on a system that requires me to create a
family of TEMP tables with the same setup. So, I have an empty TEMP parent
with each day’s data in a TEMP child.
The thing is that if I try try to run SELECT against the parent table with
the date specified in the WHERE clause, I get terrible performance despite
the fact that an EXPLAIN of the query looks fine. (The query can run for an
hour and I finally give up and kill it.) However, if I specify the child
table directly in the FROM clause, the query runs fine. (It only takes a
few minutes.)
Does partitioning of TEMP tables not work like non-TEMP tables? In the same
query, I access the parent table of a non-TEMP family and that doesn’t
cause problems.
Any idea what’s going on here?
-Ed
*Ed Behn */ Staff Engineer / Airline and Network Services
Information Management Services
2551 Riva Road, Annapolis, MD 21401 USA
Phone: (410)266-4426 / Cell: (240)696-7443
ed.behn@rockwellcollins.com
www.rockwellcollins.com
Ed Behn <ed.behn@rockwellcollins.com> writes:
Does partitioning of TEMP tables not work like non-TEMP tables?
Should be the same ... but you don't get any auto-analyze support on
a temp table. I wonder if you're remembering to ANALYZE the temp
tables after you've populated them.
regards, tom lane
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I tried that. I didn't seem to help.
*Ed Behn */ Staff Engineer / Airline and Network Services
Information Management Services
2551 Riva Road, Annapolis, MD 21401 USA
Phone: (410)266-4426 / Cell: (240)696-7443
ed.behn@rockwellcollins.com
www.rockwellcollins.com
On Mon, Jul 31, 2017 at 4:16 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Show quoted text
Ed Behn <ed.behn@rockwellcollins.com> writes:
Does partitioning of TEMP tables not work like non-TEMP tables?
Should be the same ... but you don't get any auto-analyze support on
a temp table. I wonder if you're remembering to ANALYZE the temp
tables after you've populated them.regards, tom lane
Ed Behn <ed.behn@rockwellcollins.com> writes:
I tried that. I didn't seem to help.
Well, it works in a simple test case for me. You'll need to post a
self-contained example that's not working if you want much help ...
regression=# create temp table pp(f1 int, f2 text);
CREATE TABLE
regression=# create temp table c1(check(f1 between 0 and 1)) inherits(pp);
CREATE TABLE
regression=# create temp table c2(check(f1 between 1 and 2)) inherits(pp);
CREATE TABLE
regression=# explain select * from pp where f1 < 1;
QUERY PLAN
------------------------------------------------------------
Append (cost=0.00..25.88 rows=424 width=36)
-> Seq Scan on pp (cost=0.00..0.00 rows=1 width=36)
Filter: (f1 < 1)
-> Seq Scan on c1 (cost=0.00..25.88 rows=423 width=36)
Filter: (f1 < 1)
(5 rows)
regression=# explain select * from pp where f1 > 1;
QUERY PLAN
------------------------------------------------------------
Append (cost=0.00..25.88 rows=424 width=36)
-> Seq Scan on pp (cost=0.00..0.00 rows=1 width=36)
Filter: (f1 > 1)
-> Seq Scan on c2 (cost=0.00..25.88 rows=423 width=36)
Filter: (f1 > 1)
(5 rows)
regards, tom lane
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