Performance difference between ISEMPTY and FINDFIRST

Luc_VanDyck

When you only want to know if a table contains no records (with applied filters) and you don't need the actual record(s), what to use: ISEMPTY or FINDFIRST?

recMyRec.SETCURRENTKEY(...);
recMyRec.SETRANGE(Field,...);
IF recMyRec.ISEMPTY THEN
  ...

or

recMyRec.SETCURRENTKEY(...);
recMyRec.SETRANGE(Field,...);
IF NOT(recMyRec.FINDFIRST) THEN
  ...

Is there a performance (or other) difference between the two?

Marije_Brummel

IsEmpty.

FINDFIRST will read the data from disk into memory and transport it to the client.

IsEmpty will only look in the index and return true or false.

Timo_Lässer

If I remember correctly, the difference is in the SQL Query which looks something like this:
FINDFIRST => SELECT * TOP 1
ISEMPTY => SELECT TOP 1

As you can see, ISEMPTY fetches no fields but FINDFIRST fetches the whole record.

Marije_Brummel

Timo Lässer wrote:

If I remember correctly, the difference is in the SQL Query which looks something like this:
FINDFIRST => SELECT * TOP 1
ISEMPTY => SELECT TOP 1

As you can see, ISEMPTY fetches no fields but FINDFIRST fetches the whole record.

Nope, but almost. :-s

IsEmpty does a Select Top 1 NULL FROM...

NULL means that no data is read from the table or index.

see also my Blog

http://dynamicsuser.net/blogs/mark_brum ... 07/04.aspx

Luc_VanDyck

Now I'll have to change my coding habits ;-)

Marije_Brummel

That is why we do these workshops

http://www.qurius.eu/Learning/NL/index. ... Itemid=156

O:)