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Date: Wed, 8 Feb 2006 11:11:08 -0800
From: Mamta Satoor <msatoor@gmail.com>
To: Derby Development <derby-dev@db.apache.org>
Subject: Derby-573 Optmier overrides - joinOrder and joinStrategy
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Hi,

One of optimizer overrides, that a user can specify, is joinStrategy. The
functional spec for joinStrategy says following "The joinStrategy property
can be used only within a TableExpression, *but it must be used in
conjunction with the joinOrder property. Do not let the optimizer choose th=
e
join order.*"

When I wrote the functional spec, I got this piece of information from old
Cloudscape release documentation, where the optimizer overrides were
available in a non-portable syntax. I also got some of the test cases from
that old Cloudscape release and one of the test cases is as follows
*SELECT * FROM t1 a, t1 b --DERBY-PROPERTIES joinStrategy=3Dnestedloop
WHERE a.c1=3Db.c1*
As you can see, the example above doesn't specify joinOrder override along
with joinStrategy. Should Derby (in its code) make it mandatory that
joinStrategy can't be specified w/o joinOrder? If not, then should the
functional spec be changed? What happens if user doesn't specify joinOrder
along with joinStrategy? Will joinStrategy be ignored. I haven't had a
chance to investigate this yet. I only stumbled on it last night when I was
reviewing Eric's hardwork on getting this feature documented and noticed
that the example for joinStrategy didn't include joinOrder.

thanks,
Mamta

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<div>Hi,</div>
<div>&nbsp;</div>
<div>One of optimizer overrides, that&nbsp;a user can specify, is joinStrat=
egy.&nbsp;The functional spec for joinStrategy says following &quot;The joi=
nStrategy property can be used only within a TableExpression, <u>but it mus=
t be used in conjunction with the joinOrder property. Do not let the optimi=
zer choose the join order.
</u>&quot;</div>
<div>&nbsp;</div>
<div>When I wrote the functional spec, I got this piece of information from=
 old Cloudscape release documentation, where the optimizer overrides were a=
vailable&nbsp;in a non-portable syntax. I also got some of the test cases f=
rom that old Cloudscape release and one of the test cases is as follows
</div>
<div><strong>SELECT * FROM t1 a, t1 b --DERBY-PROPERTIES joinStrategy=3Dnes=
tedloop<br>WHERE a.c1=3Db.c1</strong></div>
<div>As you can see, the example above doesn't specify joinOrder override&n=
bsp;along with joinStrategy. Should&nbsp;Derby (in its code) make it mandat=
ory that joinStrategy can't be specified w/o joinOrder? If not, then should=
 the functional spec&nbsp;be changed? What happens if user doesn't specify =
joinOrder along with joinStrategy? Will joinStrategy be ignored. I haven't =
had a chance to investigate this yet. I only stumbled on it last night when=
 I was reviewing Eric's hardwork on getting this feature documented and not=
iced that the example for joinStrategy didn't include joinOrder.=20
</div>
<div>&nbsp;</div>
<div>thanks,</div>
<div>Mamta</div>

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