Re: Set explain utility

In article <33A6397D.3519@west.co.za>, "Mark D. Stock" <marks@west.co.za> writes >MarkDenham@aol.com wrote: >> > >If you do not use PREPARE, your statement is parsed and optimised by >the OPEN. > >If you use PREPARE, your statement is parsed by the PREPARE, and >optimised by the OPEN. > >Hope that helps, Set explain output is ONLY created when you actually open the cursor, I tested this on my machine at work today (4GL 6.0x / SE 7.1x). You get syntax errors if you try to prepare something which is not valid syntax (I've had these yesterday!). Doing DATABASE djw MAIN DEFINE x CHAR(200) SET EXPLAIN ON LET x = "select * from site" PREPARE p1 FROM x DECLARE c1 CURSOR FOR p1 END MAIN no sqexplain.out produced. Doing DATABASE djw MAIN DEFINE x CHAR(200) SET EXPLAIN ON LET x = "select * from site" PREPARE p1 FROM x DECLARE c1 CURSOR FOR p1 OPEN c1 END MAIN Bingo! set sqexplain.out produced. The optimizer DEFINATELY parses statements when they are prepared. The optimizer ONLY produces sqexplain.out files when the cursor if opened. My next question is when is it optimizer, I assume when the cursor is opened since otherwise a needed index could be dropped between when the prepare is done and when the open is done... Anyone able to give a definate statement about when optimization is done? -- David Williams