Re: SQL Hidden indexes originating from constraints

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Unique constraints require a unique index...

I'm not aware of any other constraints in which an index would be built by
the system.

Charles

On Thu, Oct 21, 2021 at 11:46 AM <stefan@xxxxxxxxxx> wrote:

> Hi,
>
>
>
> Beware, I'm in deep water and may have misunderstood most of what I'm
> trying
> to explain below:
>
>
>
> Trying to analyze a bunch of ODBC requests for performance improvements and
> my starting point is to compare where-clauses to available indexes.
>
> Found a schema with a bunch of large tables - and to my surprise NO
> indexes.
> DSPLIB - no. DSPDBR - no. Went graphical at
> :2001/Databases/Schemas/Schema/Indexes - no.
>
> However I  found a bunch of constraints named Q_* that can be found at
> 2001:/ Databases/Schemas/Schema/Tables/Table-right-click/Show indexes.
>
>
>
> It seems to me that the SQL manager creates an index for every constraint
> being defined and if I run an sql-statement in Visual Explain it actually
> uses the Q_* index.
>
>
>
> Questions:
>
> Anyone knows the reason those indexes are not showed up as indexes unless I
> right click on the specific table name and click Show Indexes?
>
> Why are they hidden? I can't get usage information etc.
>
> If I'm reasonably right about these indexes being used it seems appropriate
> to add a lookup to qsys2.syskeycst in my DB relations analyze program.
>
>
>
> If I'm going to loose more hair on this I probably have to start with arms
> and legs..
>
>
>
> Thanks!
>
>
>
> Stefan
>
> --
>
>
> Stefan Tageson
>
>
>
> Mobile +46 732 369934
>
>
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>
>
>
>
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>
>
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