Re: Query planning around one key of a multi-column index

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But so are you guys!

Thanks, this is helpful.

Is it really always true that querying off any column that's not the first
column of a multi-column index will NOT use that index?


On Wed, Dec 18, 2019 at 7:02 PM Craig James <[email protected]> wrote:

> Google is your friend:
>
> http://www.postgresqltutorial.com/postgresql-indexes/postgresql-multicolumn-indexes/
>
> On Wed, Dec 18, 2019 at 4:43 PM Wells Oliver <[email protected]>
> wrote:
>
>> I've been using PG now for so many years and I don't have a solid
>> concrete answer on this in my head, and I feel like I should: if I have a
>> table with a multi-column index and I query on one of those columns (or
>> some subset of those columns), will it use that index?
>>
>> Is there more reading on this topic? I've always felt it's a little more
>> complicated but I'm not quite sure.
>>
>> --
>> Wells Oliver
>> [email protected] <[email protected]>
>>
>
>
> --
> ---------------------------------
> Craig A. James
> Chief Technology Officer
> eMolecules, Inc.
> 3430 Carmel Mountain Road, Suite 250
> San Diego, CA 92121
> ---------------------------------
>


-- 
Wells Oliver
[email protected] <[email protected]>

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<div dir=3D"ltr"><div>But so are you guys!</div><div><br></div><div>Thanks,=
 this is helpful.</div><div><br></div><div>Is it really always true that qu=
erying off any column that&#39;s not the first column of a multi-column ind=
ex will NOT use that index?</div><div><br></div></div><br><div class=3D"gma=
il_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, Dec 18, 2019 at 7:0=
2 PM Craig James &lt;<a href=3D"mailto:[email protected]">cjames@emolec=
ules.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D=
"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-le=
ft:1ex"><div dir=3D"ltr">Google is your friend:<div><a href=3D"http://www.p=
ostgresqltutorial.com/postgresql-indexes/postgresql-multicolumn-indexes/" t=
arget=3D"_blank">http://www.postgresqltutorial.com/postgresql-indexes/postg=
resql-multicolumn-indexes/</a><br></div></div><br><div class=3D"gmail_quote=
"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, Dec 18, 2019 at 4:43 PM Wel=
ls Oliver &lt;<a href=3D"mailto:[email protected]" target=3D"_blank">w=
[email protected]</a>&gt; wrote:<br></div><blockquote class=3D"gmail_qu=
ote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,20=
4);padding-left:1ex"><div dir=3D"ltr"><div>I&#39;ve been using PG now for s=
o many years and I don&#39;t have a solid concrete answer on this in my hea=
d, and I feel like I should: if I have a table with a multi-column index an=
d I query on one of those columns (or some subset of those columns), will i=
t use that index?</div><div><br></div><div>Is there more reading on this to=
pic? I&#39;ve always felt it&#39;s a little more complicated but I&#39;m no=
t quite sure.<br></div><div><br>-- <br><div dir=3D"ltr"><div dir=3D"ltr"><d=
iv>Wells Oliver<br><a href=3D"mailto:[email protected]" target=3D"_blan=
k">[email protected]</a></div></div></div></div></div>
</blockquote></div><br clear=3D"all"><div><br></div>-- <br><div dir=3D"ltr"=
><div dir=3D"ltr"><div><div dir=3D"ltr"><div><div><div>--------------------=
-------------<br>Craig A. James<br></div>Chief Technology Officer<br></div>=
eMolecules, Inc.<br></div><div>3430 Carmel Mountain Road, Suite 250</div><d=
iv>San Diego, CA 92121<br></div>---------------------------------<br></div>=
</div></div></div>
</blockquote></div><br clear=3D"all"><br>-- <br><div dir=3D"ltr" class=3D"g=
mail_signature"><div dir=3D"ltr"><div>Wells Oliver<br><a href=3D"mailto:wel=
[email protected]" target=3D"_blank">[email protected]</a></div></div=
></div>

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