Minimize calls to the database..

Question

Im trying to find out what would be the best way to minmize calls to the database..
I created a function that has to determine if a record exist on a table..
There is a cursor that loops thru another table to see if the value exist on other tables.. .. and the function is called in every loop.. but that means that it has to make a trip to the database every time..
Is there is anything like in .net datatable that i can load the entire table in memory (80.000 + records) and query from memory without having to go to the database every time ? Or is it acceptable to call the function in each loop ?
What are the tradeoff's ?
Thanks !!!

Answer 1

for stuff like this, it really depends what your bottle neck is.
if you are finding that the CPU is sitting at < 20% while your hard drive is spinning like mad, then investigate using collections (aka:associative arrays aka: pl/sql tables). to a bit of reading there's heaps of stuff out there, basic format:
declare
type type_foo is table of tbl_foo%rowtype index by binary integer;
tab_foo type_foo;
begin
select * from tbl_foo bulk collect into tab_foo;
--you can then refference each row in the collection by:
for i in 1..100 loop
dbms_output.put_line(tab_foo(i).foobar);
end loop; --this will output the first 100 foobar's.
--alternatively, if you have a number as a unique identifier in the table,
--you can use that as the table index and check for existance like the following:
if tab_foo(i).exists then
--stuff
end if;
end;
(disclaimer: the above was just off the top of my head - syntax may be slightly incorrect, RTM)
this puts the whole table in memory.
now if after doing this, you find that your cpu is sitting at 100% and your hard drive is barely spinning, then you've potentially not solved your problem. check how long it takes - if one is not significantly faster than the other, then investigate other ways of speading it up (indexes, hints etc.)
if you use a collection and you get 100% memory usage AND your hard drive is spinning like crazy, you've perhaps used too much memory and the server's using the swap file, defeating the purpose of putting something in memory in the first place.
anyway, try it and see :D