Re: proposal: plpgsql - iteration over fields of rec or row variable

>>
>> What is solution in your design?
>
> nothing specific.   My main interest is in the plan management portion
> (only because of side interest in search_path which is complete mess
> at present).  if plpgsql_compile knows that it is trigger function and
> which table fired the trigger, you can generate specific hash key, and
> take advantage of new/old being well defined inside function
> execution.  This seems less fiddly than trying to deal with plan
> mechanics inside the function.  My knowledge stops there -- I don't
> have a real good understanding of how plpgsql works internally.  If
> this idea passes smell test maybe it merits more research.
>

I still don't understand how it can be used for iteration over record?

The basic question is - what tasks we have to solve?

a) general constraints over fields
b) general initialization over fields
c) custom record serialization/deserialization - audits, logs, delta
compression, custom formatting (xml, json)

Next question - what breaks we have to across?
a) using a different types for some fields - invalid plans
b) lost of type info
c) toast / detoast overhead
d) text / binary transformation

Possible way:

a) transformation to common type

+ simple - it is one day job - function record_to_array,
array_to_record, and fieldnames_to_array
- lost of type info, hidden problems with IO cast - int a := 10.0/2.0
is a problem

using a plperl, pltcl is same like @a

b) FOR OVER or similar loop
+ there are not text / binary cast
- necessary to introduce a new concept - a multiple instances of loop's body
- longer cache of plans, but it must not be terrible - instance is
per distinct field type not per type

c) LAMBDA calcul? - maybe Merlin's idea
+ there are not text / binary cast
+ probably not necessary changes inside plpgsql
- it's far to ADA - or do you know any lambda in ADA or PL/SQL?
- probably higher overhead with detoast
- probably higher overhead with function call

is this review complete? any other ideas?

Regards

Pavel

> merlin
>