CODEWITHSUNDEEP
progress-4glopenedge
Bill
Bill

Reputation: 1247

what is the efficiency of an assign statement in progress-4gl

why is an assign statement more efficient than not using assign?

co-workers say that:

assign
  a=3
  v=7
  w=8.

is more efficient than:

a=3.
v=7.
w=8.

why?

Upvotes: 4

Views: 2725

Answers (3)

Tom Bascom
Tom Bascom

Reputation: 14020

You could always test it yourself and see... but, yes, it is slightly more efficient. Or it was the last time I tested it. The reason is that the compiler combines the statements and the resulting r-code is a bit smaller.

But efficiency is almost always a poor reason to do it. Saving a micro-second here and there pales next to avoiding disk IO or picking a more efficient algorithm. Good reasons:

  1. Back in the dark ages there was a limit of 63k of r-code per program. Combining statements with ASSIGN was a way to reduce the size of r-code and stay under that limit (ok, that might not be a "good" reason). One additional way this helps is that you could also often avoid a DO ... END pair and further reduce r-code size.

  2. When creating or updating a record the fields that are part of an index will be written back to the database as they are assigned (not at the end of the transaction) -- grouping all assignments into a single statement helps to avoid inconsistent dirty reads. Grouping the indexed fields into a single ASSIGN avoids writing the index entries multiple times. (This is probably the best reason to use ASSIGN.)

  3. Readability -- you can argue that grouping consecutive assignments more clearly shows your intent and is thus more readable. (I like this reason but not everyone agrees.)

Upvotes: 7

AquaAlex
AquaAlex

Reputation: 380

basically doing:

a=3.
v=7.
w=8.

is the same as: 

assign a=3.
assign v=7.
assign w=8.

which is 3 separate statements so a little more overhead. Therefore less efficient.

Progress does assign as one statement whether there is 1 or more variables being assigned. If you do not say Assign then it is assumed so you will do 3 statements instead of 1. There is a 20% - 40% reduction in R Code and a 15% - 20% performance improvement when using one assign statement. Why this is can only be speculated on as I can not find any source with information on why this is. For database fields and especially key/index fields it makes perfect sense. For variables I can only assume it has to do with how progress manages its buffers and copies data to and from buffers.

Upvotes: 1

ilovebigmacs
ilovebigmacs

Reputation: 993

ASSIGN will combine multiple statements into one. If a, v and w are fields in your db, that means it will do something like INSERT INTO (a,v,w)...

rather than INSERT INTO (a)... INSERT INTO (v)

etc.

Upvotes: 0

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