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compiling queries

Posted on 2013-01-29
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Last Modified: 2013-01-30
I noticed when starting from a blank database and importing in many queries from an older database the forms are terribly slow when opening. I think I found the reason but still need a little help. It seems since the queries have never been opened the have never been compiled. If I open them, show the data, then close, the forms seems to open faster.

If this is the case is there a way to open and close or compile all the queries in vb?
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Question by:Shawn
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15 Comments
 
LVL 75
ID: 38832822
"If I open them, show the data, then close, the forms seems to open faster."

That is because the JET query execution plan is recreated based on current datasets. So, effectively - you have 'recompiled' the queries.

"If this is the case is there a way to open and close or compile all the queries in vb?"
I'm thinking if in vba, you open each QueryDef and then save/close ... this may do the same thing.

mx
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LVL 120

Expert Comment

by:Rey Obrero (Capricorn1)
ID: 38832833
the first time the query executes, the query will be compiled, then the compiled query is used when the query is executed.
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LVL 58

Accepted Solution

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Jim Dettman (Microsoft MVP/ EE MVE) earned 334 total points
ID: 38832847
That is correct.  This occurs after a compact and repair as well.

What's happening is that the plan for query execution is being generated and saved.

I don't have code off-hand to open and execute every query, but for the most part, you could do it in VBA.

However it would depend on the queries and how they were writen as to how easy or complete it would be.

 What you would need to do would depend on the type  (action, select, pass-through), what they are doing (ie. tied to a form), and if they must be done in sequence (ie. make table, then appends after that).

Jim.
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LVL 75
ID: 38832848
Maybe something like this (make a backup first).  I just tried this - but I have no way to tell on this system if it makes a difference.

    Dim qdf As dao.QueryDef
    Dim db As dao.Database
    Set db = CurrentDb
    For Each qdf In db.QueryDefs
         Debug.Print qdf.Name
         On Error Resume Next  ' in case query has systax error, like some of my EE qrys.
        qdf.sql = qdf.sql
        Err.Clear
        qdf.Close
    Next qdf
   
    Set qdf = Nothing
    Set db = Nothing
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LVL 58
ID: 38832852
<<I'm thinking if in vba, you open each QueryDef and then save/close ... this may do the same thing.>>

 Has to be a open of the query def, modification of the SQL, a save, and then a execute of the query without a save after that to force a re-compile.

Jim.
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LVL 75
ID: 38832941
"a save"
So how do you actually 'save' in vba ?  Say relative to the code I posted.
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LVL 58
ID: 38833092
There's no code equivalent.   Just setting the property seems to be enough, although it may be when it goes out of scope or is closed that the save actually takes place.  I've never really pinned it down.

 When I answered though, I was thinking of the steps I'd do manually, so I really didn't answer that correctly.

 A execution is required though, which is where doing this in code becomes a problem depending on how the queries are written.

Jim.
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LVL 75
ID: 38833118
Execute - yeah, that's what I suspected - and yes, problematic in code most likely.

The good news: Compact & Repair.

mx
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LVL 1

Author Comment

by:Shawn
ID: 38833151
does Compact & Repair really compile the queries though?
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LVL 58

Assisted Solution

by:Jim Dettman (Microsoft MVP/ EE MVE)
Jim Dettman (Microsoft MVP/ EE MVE) earned 334 total points
ID: 38835162
<<does Compact & Repair really compile the queries though?>>

  It doesn't compile them.  What it does is flag them as not compiled, so first time they are run, they are re-compiled.

 That's one of the reasons I've never bothered with trying to compile all queries before I deliver something...it's just not worth the effort.

Jim.
0
 
LVL 1

Author Comment

by:Shawn
ID: 38835886
>>so first time they are run, they are re-compiled.
even when theyare behind a form or do they still have to be run/opened directly?
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LVL 58
ID: 38835926
<<even when theyare behind a form or do they still have to be run/opened directly? >>

 That was my point earlier; many won't run outside of a certain situation, such as a form being opened.

Jim.
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LVL 1

Author Comment

by:Shawn
ID: 38835936
ok, thanks Jim. You just saved me a lot of time. :-)

Shawn
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LVL 75

Assisted Solution

by:DatabaseMX (Joe Anderson - Microsoft MVP, Access and Data Platform)
DatabaseMX (Joe Anderson - Microsoft MVP, Access and Data Platform) earned 166 total points
ID: 38836425
"even when theyare behind a form "
I believe they are still flagged for recompile (after a C&R) since they do appear in the QueryDef collection - show as (example):

~sq_ffrmLstBox

Thing is ... since C&R only flags queries for recompile ... this may be why - you experience slowness - at various times - when a given query is actual recompiled upon first use after a C&R.  However, how today's machines this may be so fast that is't negligible - probably hard to measure/determine.

mx
0
 
LVL 1

Author Closing Comment

by:Shawn
ID: 38837234
thanks for helpin g me understand. So solution is we don't need vb but a C&R. C&R sure comes in handy.
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