Deterministic stored functions in FB 3: provide ability to map input arguments
to output values
-----------------------------------------------------------------------------------------------
Key: CORE-4361
URL: http://tracker.firebirdsql.org/browse/CORE-4361
Project: Firebird Core
Issue Type: Improvement
Reporter: Pavel Zotov
Priority: Minor
DDL:
set term ^;
recreate function fx(a_n int) returns varchar(31) deterministic as
begin
return (select rt.rdb$type_name from rdb$types rt order by rt.rdb$type rows
(:a_n) to (:a_n));
end
^set term ;^
Test-1: select fx(10) from rdb$formats rows 1
Trace-1:
select fx(10) from rdb$formats rows 1
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
PLAN (RDB$FORMATS NATURAL)
1 records fetched
0 ms, 519 fetch(es)
Table Natural
unge
******************************************
****
RDB$FORMATS 1
RDB$TYPES 251
Test-2: select fx(10) from rdb$formats rows 5;
Trace-2:
Statement 30:
------------------------------------------
select fx(10) from rdb$formats rows 5
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
PLAN (RDB$FORMATS NATURAL)
5 records fetched
1 ms, 2585 fetch(es)
Table Natural
unge
******************************************
****
RDB$FORMATS 5
RDB$TYPES 1255
So, stored function re-reads RDB$TYPES table for each row of source.
It will be good for performance if all input arguments will be mapped to output
results of such functions.
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