[SQL lab] Fixed limit issue

[conglei]

This PR is to fix the issue #5272

The original Regular Expression cannot catch the LIMIT statement when there are extra statements after LIMIT.

Note, the proposed solution is not perfect either.. Currently all the corner case I can think of:

• 'LIMIT' inside quotes, which causes the false setting of query.limit
  SELECT "LIMIT 100" as C, id from aTable

• LIMIT number is set larger than SQL_MAX_ROW, which causes the additional limit clause added
  SELECT * FROM atable LIMIT 10000001 OFFSET 1

• get_query_without_limit function is broken too for the cases shown above.

[mistercrunch]

Can you add a unit test preventing regression on this specific issue?

[timifasubaa]

How about we selected everything after the number after the limit and also passed that remaining text along to the caller so the caller can do something lie "{before_limit} {new_limit} {after_limit}" That should fix problem 3 (adding the things after the limit). And to do that, we will just change this line to to (.*$) and pass the whole regex results tuple.

[john-bodley]

#5295