On Wed, Aug 19, 2009 at 3:53 AM, Tom Lanet...@sss.pgh.pa.us wrote:
* The expression might throw an error for some inputs, for instance
(1 / field) 0.5
which would fail on zero. We could recover by wrapping the whole
estimation process in a subtransaction, but that seems really
On Wed, Aug 19, 2009 at 3:16 PM, Greg Starkgsst...@mit.edu wrote:
On Wed, Aug 19, 2009 at 3:53 AM, Tom Lanet...@sss.pgh.pa.us wrote:
* The expression might throw an error for some inputs, for instance
(1 / field) 0.5
which would fail on zero. We could recover by wrapping the whole
Greg Stark gsst...@mit.edu writes:
We could add another flag in pg_proc for functions which cannot throw
an error. Perhaps all index operator class operators be required to
use such functions too?
It would be an extremely small set. For starters, anything that returns
a pass-by-reference data
Greg Stark gsst...@mit.edu writes:
Another thought. In the above case it would actually be fine to catch
the error with PG_TRY() without a subtransaction. As long as no shared
database state has been modified when the error is thrown then the
subtransaction isn't needed to roll them back.
I
On Wed, Aug 19, 2009 at 7:22 PM, Tom Lanet...@sss.pgh.pa.us wrote:
It may be that a subtransaction will actually be acceptable overhead,
as long as we don't go overboard and invoke this mechanism for simple
WHERE clauses. Hard to tell without coding it up and testing it though.
Are you
Greg Stark gsst...@mit.edu writes:
On Wed, Aug 19, 2009 at 7:22 PM, Tom Lanet...@sss.pgh.pa.us wrote:
It may be that a subtransaction will actually be acceptable overhead,
as long as we don't go overboard and invoke this mechanism for simple
WHERE clauses. Hard to tell without coding it up
Tom, Greg, Robert,
Here's my suggestion:
1. First, estimate the cost of the node with a very pessimistic (50%?)
selectivity for the calculation.
2. If the cost hits a certain threshold, then run the calculation
estimation on the histogram.
That way, we avoid the subtransaction and other
On Wed, Aug 19, 2009 at 3:00 PM, Josh Berkusj...@agliodbs.com wrote:
Tom, Greg, Robert,
Here's my suggestion:
1. First, estimate the cost of the node with a very pessimistic (50%?)
selectivity for the calculation.
There is no such thing as a pessimistic selectivity estimation. Right
now a
There were two different complaints today about the planner's inability
to make good estimates for WHERE conditions involving bit AND tests,
such as
(field 8) = 0
(field 8) 0
(field 127) = field
I'm not particularly eager to try to put in special-case knowledge
for
On Tue, Aug 18, 2009 at 10:53 PM, Tom Lanet...@sss.pgh.pa.us wrote:
There were two different complaints today about the planner's inability
to make good estimates for WHERE conditions involving bit AND tests,
such as
(field 8) = 0
(field 8) 0
(field 127) = field
10 matches
Mail list logo
