Description:
PreparedStatement.getMetaData () returns null instead of asking server for metadata.

Despite server fully supports sql statements like "-- Comment here\nSELECT..." JDBC
drivers has some code that do some kind of sql statement precheck before sending statement
to server. As far driver has no such support for comments it decides wrong about need to
ask server for metadata.

This problem slightly relates to BUG#25025 as far initial suggestion for bug fix was to
introduce support for comments in the begining of sql statement.

My need for such kind of comments is to avoid NetBeans (Visual Web Pack) from reformatting
sql statement text. Since IDE can not parse statement none changes is done. Easiest way to
achieve it is to add comment to beginning of sql statement. Current implementation of
driver hangs some functions of IDE with NullPointerException, select statement columns can
not be identified etc.

As far server side supports such statements and I can not find mention of any constraints
about location of comments I can not see why not support them.

How to repeat:
PreparedStatement stmt = conn.prepareStatement ("-- Comment\nSELECT somefield FROM
sometable") ;
ResultSetMetaData rsmd = stmt.getMetaData () ;
if (rsmd == null) {
  System.out.println ("NULL meta data!") ;
}

Suggested fix:
Allow comments to be embedded before the insert.

I will post fixed version of com.mysql.jdbc.StringUtils into java@lists.mysql.com

Sounds like a duplicate of BUG#27400 (fixed in 5.0.6 which has already been released).

Sorry, not a duplicate, slightly different.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/26881

Implementation for comments in the beginning of sql statement

Attachment: StringUtils.java (text/java), 43.01 KiB.

Test code for bugfix

Attachment: TestComments.java (text/java), 1.37 KiB.

Ansis, thanks for your report and patch provided but, as you can see, Mark has already
wrote one.

Since there is a working driver it is OK for me. :) My implementation of
StringUtils.getOffset() could be more correct on comments skipping than
Statement.findStartOfStatement() except handling not-finished comments. My implementation
will return end of statement as result, but Mark's one - beginning. In both cases
statement is incorrect.

My thinking was rather than put a full-fledged SQL parser in the driver, we'll let the
server deal with the eventual syntax error that will result from a non-terminated comment.

This has been documented in the 5.0.7 changelog: 

PreparedStatement.getMetaData() for statements containing leading one-line comments is not
returned correctly.

As part of this fix, we also overhauled detection of DML for executeQuery() and SELECTs
for executeUpdate() in plain and prepared statements to be aware of the same types of
comments.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/33375

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/33832

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/33909

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/34839

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/34840

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/34855

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/35011

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/35407

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/35410

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/35414

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/38019

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/38024