What is the Oracle PL SQL -- rule

Question

I looked through the Oracle Optimizer Hints documentation but couldn't locate a specific reference for a —+rule. This rule appears to be an out-of-date remnant from a code generating tool that was intended to replace "—+rule" with user or produced /*+ SQL */ hint code.

What are your thoughts? Does the —+rule code in the above example [literally] do anything? or should I just throw it away?

Oracle 10g2 with the most recent supported upgrades, Delphi 6 with Direct Oracle Access components. The majority of the Legacy SQL code was written for Oracle 7 and 8.

My query:

SELECT --+rule
  userid,
  username
FROM
  users
ORDER BY
  userid

Answer 1

The answer is in the material you provided as a reference:

Within a statement block, the following syntax demonstrates suggestions included in both forms of comments that Oracle allows.

{DELETE|INSERT|MERGE|SELECT|UPDATE} /*+ hint [text] [hint[text]]... */

or

{DELETE|INSERT|MERGE|SELECT|UPDATE} --+ hint [text] [hint[text]]...

The --+ hint format requires that the hint be on only one line.

So it was a syntactic rule for hints that was permitted, but I don't think I've ever seen it.

The "rule" hint in Oracle SQL refers to using the Rule Based Optimizer (RBO) rather than the CBO (Cost Based Optimizer), which has been deprecated since Oracle 10. As a result, you cannot dismiss Oracle: it should be considered, but without assistance.