Re: Faster key lookup

[Jonathan Ball <jonball52@xxxxxxxxx>]

Some pretty good alternatives offered by others.  Here is mine.  It 
appears you don't really care about the exact number of rows in the 
table that match the WHERE predicate.  All you want to know is if it is 
zero or not zero, i.e.  "at least one".

With that in mind, change the query as follows:

  EXEC SQL
    Select 1
      Into :rc
      From MY_TABLE
      Where COLUMN1 = :local1 and COLUMN2 = :local2 and COLUMN3 = :local3
             And (COLUMN4 = :local4 or :local4 = '')
    Fetch first 1 row only
  Return (SQLSTATE = '00000' and rc > 0);

There should be an index with the four COLUMNx columns in place.

On 6/27/2018 5:30 PM, Justin Taylor wrote:
> I have a *SRVPGM that calls a procedure a lot, and I need to speed it up.
>
> Here's the entire code for the procedure:
> EXEC SQL
>    Select count(*)
>      Into :rc
>      From MY_TABLE
>      Where COLUMN1 = :local1 and COLUMN2 = :local2 and COLUMN3 = :local3
>             And (COLUMN4 = :local4 or :local4 = '');
> Return (SQLSTATE = '00000' and rc > 0);
>
> MY_TABLE is reloaded once a day and is otherwise static.  It has 9K rows that are 24 bytes long (it only has the 4 columns).
>
> I know I could do a CHAIN and gain a little bit, but I'm hoping for more.  My thought is to on the first call, read the entire table into a sorted array and have the procedure do a couple of %lookup()'s.  Is there a better way?
>
> TIA