Problem
=======

Replicating from older to newer MySQL server versions may lead to
ER_PARSE_ERROR on replication applier threads because of, for example,
the workload is creating a table using a name that on the older server
version is now a reserved word.

One common workaround fix for this issue DBAs/operators do is to apply
the offending transaction manually (changing it enough to be applied
without errors) and making the replication applier thread to skip the
offending transaction already present on slaves relay log.

When GTID_MODE is ON, the recommended way of making the replication
applier to skip a transaction is to commit its GTID with an empty
transactions (or with the replacement transaction), but GTID auto skip
was not working for statements leading to ER_PARSE_ERROR.

Analysis
========

GTID auto skip functionality depends on MySQL parser for:

- Not skip "innocent" statements.

  Here, "innocent" includes SET, SHOW, SELECT, DO, USE, and empty query,
  unless it invokes a stored function.

  The reason we allow innocent statements to execute even within skipped
  transactions is that they can be useful for testing and debugging.
  E.g., we want to run SELECT @@session.gtid_owned to check that there
  is not a bug that makes the server acquire ownership.

- Keep track of transaction boundaries.

  When applying a workload dumped from mysqlbinlog client program, even
  skipping statements from already applied transactions, the client
  session applying the workload must known if a statement is a DDL or a
  DML (if it is supposed to be wrapped with "BEGIN/COMMIT" or not).

Fix
===

This patch will make the replication applier thread to ignore
ER_PARSE_ERROR when applying query events if the transaction being
applied is also being GTID auto skipped.

Making workloads dumped from mysqlbinlog to also work with GTID auto
skip when some statements lead to ER_PARSE_ERROR is too risk, as the
GTID enforcement logic could not be guaranteed without having detailed
information about the offending statement.