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From: Sunay Tripathi <sunay@henna.iitd.ernet.in>
To: postgres@postgres.Berkeley.EDU
Subject: Query order
Date: Sun, 2 Apr 95 19:09:23 GMT+5:30
Message-ID: <9504021339.AA14011@henna.iitd.ernet.in> (raw)

Dear friends,

I am running postgres v4r2 on Solaris 2.3. I have a single table in which I
have 6 attributes (all of type text).

Table Name = Info
Attributes (fields) = Name Street City State Zip Country

I also have a user defined function sub_srch which takes as argument two
strings and if the search string is a sub string, it returns true.

Now, I give a simple query

* retrieve (Info.all) where Info.City="CUPERTINO" and Info.State="CA" and
sub_srch(Info.Name, "smith") \g


I want it to find all the smiths in city CUPERTINO in state CA.

Now the question -

How will the query be processed. Will all the records having Info.City =
CUPERTINO be selected first and then of those selected, it will select
the ones that have Info.State = CA and then from those the smiths or . ...

I mean, what is the order. Right now, the postgres backends first selects
all the smith by using my function and then of those selected it checks
for city and state.

For some other queries, it works in reverse order. There has to be some order
while processing the query.

I will be much obliged if anyone can give me some idea. 

Thanks

Sunay Tripathi
Dept. of CSE,
IIT Delhi

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