ExecQual evaluates join conditions one at a time.It captures one condition and passes it to function ExecEvalExpr which is actually a macro that invokes another function evalfunc( which is a function pointer that is set to the function PostgreSQL wants to use to evaluate the expression. It's of
type:
typedef Datum (*ExprStateEvalFunc) (ExprState *expression,
ExprContext *econtext,
bool *isNull,
ExprDoneCond *isDone);

The actual function called is probably be one of the ones in backend/executor/execQual.c.
In execQual.c there are routines for evaluating each type of exprState nodes. Routines are normally called via the ExecEvalExpr macro.
Every function in execQual.c calls ExecEvalExpr macro by passing it as argument containing object of ExprState which consist of evalfunc(routine) to call for execution of node.

I am not able to find out definition of function that is passed to ExecEvalExpr macro using an object of ExprState type.
Please help me if you understand the problem.
Basically I want to know the defination of function where join conditions are evaluated(for example may be for Nested Loop Joins)
Thanx in advance
Esha



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If I understood your question, the following info may be what you're looking
for.

ExecNestLoop gets the join qualifications and passes them to ExecQual for
each outer tuple. Each qualification is checked in ExecQual using the
ExecEvalExpr macro which calls the function pointer evalfunc for each
ExprState. Iff a FALSE qualification result is found, qualification fails
and a FALSE is returned for that tuple. The functions used for
ExprState->evalfunc are defined in ExecInitExpr for each nodeTag.

Is that what you were looking for?


On 10/12/05, Esha Palta <esha@it.iitb.ac.in> wrote:
>
> ExecQual evaluates join conditions one at a time.It captures one condition
> and passes it to function ExecEvalExpr which is actually a macro that
> invokes another function evalfunc( which is a function pointer that is set
> to the function PostgreSQL wants to use to evaluate the expression. It's of
> type:
> typedef Datum (*ExprStateEvalFunc) (ExprState *expression,
> ExprContext *econtext,
> bool *isNull,
> ExprDoneCond *isDone);
>
> The actual function called is probably be one of the ones in
> backend/executor/execQual.c.
> In execQual.c there are routines for evaluating each type of exprState
> nodes. Routines are normally called via the ExecEvalExpr macro.
> Every function in execQual.c calls ExecEvalExpr macro by passing it as
> argument containing object of ExprState which consist of evalfunc(routine)
> to call for execution of node.
>
> I am not able to find out definition of function that is passed to
> ExecEvalExpr macro using an object of ExprState type.
> Please help me if you understand the problem.
> Basically I want to know the defination of function where join conditions
> are evaluated(for example may be for Nested Loop Joins)
> Thanx in advance
> Esha
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Have you searched our list archives?
>
> http://archives.postgresql.org
>



--
Respectfully,

Jonah H. Harris, Database Internals Architect
EnterpriseDB Corporation
http://www.enterprisedb.com/