Dynamic boolean expression evaluation

Hey everyone,
We have a table that consists of a couple key columns and a column containing a boolean expression. We want to select a number of rows based on the key columns and evaluate the boolean expression in the expression column for each, only returning the first row wherein the boolean expression evaluates to true.
We are using a context to inject the test variables into the boolean expressions and currently we are selecting all the key rows in a PL/SQL procedure and going through the cursor evaluating each of the boolean expressions with an execute immediate.
The expressions are currently formated in the columns as anonymous PL/SQL blocks that, when called, will either return true or false to the PL/SQL procedure. Upon returning true, the procedure stops looping and returns true to the caller.
Psuedo-code would be:
- set-up sys_context with condition variables
- create cursor for: select * from expression_tbl et where <key matches>
- begin loop through cursor
- execute immediate cursor_row.expression using out :out_is_true
- if out_is_true = 'Y' then return true
- loop
- return false
The expressions (anonymous PL/SQL blocks) from the table look something like this:
begin if ((''||sys_context('ctx', '1')||'' = 'FL') AND (''||sys_context('ctx', '3')||'' BETWEEN 1619 AND 4598) ) then :1 := 'Y'; end if; end;
This works, but it seems like I should be able to do this another way and potentially extract more performance.
So...a couple questions:
1) I have read on ask Tom that a dynamic select statement (rather than an anonymous PL/SQL block) can evaulate the boolean expressions. I.E. rather than use an execute immediate clause on an anonymous PL/SQL block contained in the expression column, I would make the expression column compatible with a where clause and create this dynamic SQL query: 'select count(*) from dual where ' || expression. I would then execute that query and if it returns a row then the expression is true, otherwise it is false. My question is, does anyone think the performance of parsing the SQL and executing it would be better than that of executing an anonymous PL/SQL block for every row? Tom said that the SQL could incur a lot of hard-parses and kill performance, but how deathly is the constant compilation of anonymous PL/SQL blocks as shown above in comparison?
2) Would there be any benefit to pulling the execute routines out of the PL/SQL block and issuing a query such as the following:
select * from expression_tbl et where <key matches> AND pkg.eval_routine(et.expression) = 'Y' AND rownum <= 1.
I realize that the evaulating routine would then need to either perform an execute immediate on et.expression (if we keep the current method in place) or formulate the dynamic SQL statement and execute it. But, could this be faster than doing the same loop through rows explicitely in PL/SQL?
Doing this would trim my PL/SQL down to:
- set up sys_context
- execute the above select statmenet
- if a row is returned then return true otherwise return false
Seems more elegant, but the peformance is all that matters.
3) Is there any built-in routine that I may be able to replace pkg.eval_routine from 2 with that would evaulate boolean expressions for me? Or any other way to inline the idea from 1 with 2? I can't think of one given the dynamic nature of the beast, but...maybe there's something I missed.
Thanks everyone! Hopefully I've expressed myself clearly.

Brian - According to Tom Kyte Doing PL/SQL inside Execute Immediate should be faster as you are already within the context of a PL/SQL engine. If we choose to do it in SQL then the PL/SQL engine has to hand it over to the SQL Engine for executing the dynamic Select statements and so might be a little slower. But I am not sure if the difference can be quantifiable unless u do your own test of both evaluators and run them for like a few thousand times in a loop.
If you are using 10g R2 - you might want to look into DBMS_RLMGR package which is the API for the Oracle's version of the embedded business rule manager.
I looked into it but it didn't fit our needs as its deficient with respect to rule versioning and effective and until date based business rule enforcement/ validation.
After taking a shot at designing something home grown I feel its not that difficult to construct one that fit our needs inclusive of the features( rule versioning, effective and until dates) that I listed above as deficiencies in the Oracle embedded rule engine.
If you don't have those requirements may be using the Business Rule manager API of 10g R2 might not be a bad anticipating it will be improved in future versions.
Regards
-Suren

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    at http://www.consideringred.com/files/oracle/2012/EvaluatedMoreThanOnceApp-v0.02.zip
    It shows that the isMyCImageLinkRendered() method is called during the jsfRenderResponse phase:
    MyLogPagePhaseListener.beforePhase() : ( 9) jsfRestoreView : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 9) jsfRestoreView
    MyLogPagePhaseListener.beforePhase() : ( 9) jsfRestoreView : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 9) jsfRestoreView
    MyLogPagePhaseListener.beforePhase() : ( 0) initContext : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 0) initContext
    MyLogPagePhaseListener.beforePhase() : ( 1) prepareModel : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 1) prepareModel
    MyLogPagePhaseListener.beforePhase() : (14) jsfRenderResponse : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.beforePhase() : ( 8) prepareRender : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 8) prepareRender
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 1
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 2
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 3
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 4
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 5
    MyLogPagePhaseListener.afterPhase()  : (14) jsfRenderResponseIf the link is clicked, it also seems to be called during the phases jsfApplyRequestValues, jsfProcessValidations and jsfUpdateModelValues, resulting 8 calls:
    MyLogPagePhaseListener.beforePhase() : ( 0) initContext : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 0) initContext
    MyLogPagePhaseListener.beforePhase() : ( 1) prepareModel : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 1) prepareModel
    MyLogPagePhaseListener.beforePhase() : (10) jsfApplyRequestValues : /faces : /tryCommandImageLink
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 1
    MyLogPagePhaseListener.afterPhase()  : (10) jsfApplyRequestValues
    MyLogPagePhaseListener.beforePhase() : (11) jsfProcessValidations : /faces : /tryCommandImageLink
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 2
    MyLogPagePhaseListener.afterPhase()  : (11) jsfProcessValidations
    MyLogPagePhaseListener.beforePhase() : (12) jsfUpdateModelValues : /faces : /tryCommandImageLink
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 3
    MyLogPagePhaseListener.afterPhase()  : (12) jsfUpdateModelValues
    MyLogPagePhaseListener.beforePhase() : ( 5) validateModelUpdates : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 5) validateModelUpdates
    MyLogPagePhaseListener.beforePhase() : (13) jsfInvokeApplication : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : (13) jsfInvokeApplication
    MyLogPagePhaseListener.beforePhase() : ( 7) metadataCommit : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 7) metadataCommit
    MyLogPagePhaseListener.beforePhase() : (14) jsfRenderResponse : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.beforePhase() : ( 8) prepareRender : /faces : /tryCommandImageLink
    MyLogPagePhaseListener.afterPhase()  : ( 8) prepareRender
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 4
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 5
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 6
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 7
    TryCommandImageLink.isMyCImageLinkRendered() : begin : count = 8
    MyLogPagePhaseListener.afterPhase()  : (14) jsfRenderResponse
    John Stegeman wrote:... 2). Does the same behaviour occur with the visible property?In a similar way I tried:
    <af:commandImageLink text="commandImageLink to try visible" id="cil1"
                         visible="#{r_tryCImageLinkVisible.myCImageLinkVisible}"/>This results in 2 calls during the jsfRenderResponse phase:
    MyLogPagePhaseListener.beforePhase() : ( 9) jsfRestoreView : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 9) jsfRestoreView
    MyLogPagePhaseListener.beforePhase() : ( 9) jsfRestoreView : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 9) jsfRestoreView
    MyLogPagePhaseListener.beforePhase() : ( 0) initContext : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 0) initContext
    MyLogPagePhaseListener.beforePhase() : ( 1) prepareModel : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 1) prepareModel
    MyLogPagePhaseListener.beforePhase() : (14) jsfRenderResponse : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.beforePhase() : ( 8) prepareRender : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 8) prepareRender
    TryCImageLinkVisible.isMyCImageLinkVisible() : begin : count = 1
    TryCImageLinkVisible.isMyCImageLinkVisible() : begin : count = 2
    MyLogPagePhaseListener.afterPhase()  : (14) jsfRenderResponseIf the link is clicked, still 2 calls during the jsfRenderResponse phase:
    MyLogPagePhaseListener.beforePhase() : ( 0) initContext : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 0) initContext
    MyLogPagePhaseListener.beforePhase() : ( 1) prepareModel : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 1) prepareModel
    MyLogPagePhaseListener.beforePhase() : (10) jsfApplyRequestValues : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : (10) jsfApplyRequestValues
    MyLogPagePhaseListener.beforePhase() : (11) jsfProcessValidations : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : (11) jsfProcessValidations
    MyLogPagePhaseListener.beforePhase() : (12) jsfUpdateModelValues : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : (12) jsfUpdateModelValues
    MyLogPagePhaseListener.beforePhase() : ( 5) validateModelUpdates : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 5) validateModelUpdates
    MyLogPagePhaseListener.beforePhase() : (13) jsfInvokeApplication : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : (13) jsfInvokeApplication
    MyLogPagePhaseListener.beforePhase() : ( 7) metadataCommit : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 7) metadataCommit
    MyLogPagePhaseListener.beforePhase() : (14) jsfRenderResponse : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.beforePhase() : ( 8) prepareRender : /faces : /tryCImageLinkVisible
    MyLogPagePhaseListener.afterPhase()  : ( 8) prepareRender
    TryCImageLinkVisible.isMyCImageLinkVisible() : begin : count = 1
    TryCImageLinkVisible.isMyCImageLinkVisible() : begin : count = 2
    MyLogPagePhaseListener.afterPhase()  : (14) jsfRenderResponseQuestion (q1) remains.
    regards
    Jan

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