19.04.2012 20:30, Rick Debay wrote:
I will, after we migrate to FB 2.5.x. Right now we're still on 1.5.6.
This may explain your plan issue. I don't expect you facing it again
after migration.
Dmitry
unordained schrieb am 11.04.2012 um 15:18 (-0500):
I once worked on medical software (with Firebird!) and we had to
deal with ICD-9 and CPT-4 codes. The coding mechanism is somewhat
hierarchical: code 201 might mean something, and 201.1 might be
more specific, and 201.12 might be even *more*
11.04.2012 1:49, unordained wrote:
select 1 from bt_dchronexpl inner join bt_ref on bt_ref.file_num =
bt_dchronexpl.filenumber;
-- PLAN JOIN (BT_DCHRONEXPL NATURAL, BT_REF INDEX (IX_BT_REF_FILE_NUM_ASC))
-- so it CAN use an index, but why not both? just the size imbalance?
It's impossible to
-- Original Message ---
From: Dmitry Yemanov dim...@users.sourceforge.net
select 1 from bt_dchronexpl inner join bt_ref on bt_ref.file_num =
bt_dchronexpl.filenumber;
-- PLAN JOIN (BT_DCHRONEXPL NATURAL, BT_REF INDEX (IX_BT_REF_FILE_NUM_ASC))
-- so it CAN use an index, but
11.04.2012 19:09, unordained wrote:
a) for every row in A (regardless of order), do a PK lookup in B [which,
ignoring index-caching, or some implementation tweak to remember where
in the
index you last were as a best-guess for the next lookup, is wasteful,
as it would restart from the root
Dmitry,
Still, this doesn't explain why I do see it sometimes using an index to
support a starts-with join, and he doesn't.
I can hardly guess without a test case.
Way back in the message chain was an example. If I understood it
correctly, it was something like this:
create table core
Ann,
Way back in the message chain was an example.
I remember the example, but IIRC there was no DDL provided. And I recall
that the FB version wasn't specified either. My crystal ball tends to
fail in such unclear conditions.
create table core (coreName varchar(30), coreCode char (2));
Dmitry,
As expected, it does use the index.
And if this test does use the index, then you'll need
a test with ddl and possibly data from the original author.
This is what I'm asking for :-)
Right. And perhaps the author can think about the differences between
the case that appears not
-- Original Message ---
From: Ann Harrison aharri...@ibphoenix.com
And what part of relational theory allows partial matches on keys.
Ann
--- End of Original Message ---
H.
Codd might disagree with the incomplete normalization of his base tables, but
relational
-- Original Message ---
From: Dmitry Yemanov dim...@users.sourceforge.net
This is known as a nested loop join. And restart from the root costs
just a couple of page reads that are likely to be satisfied using the
cache. Not something really wasteful.
2) Streams are read in
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