[MDEV-23792] Add methods to disable some of optimizations/rewrites Created: 2020-09-22  Updated: 2022-02-22

Status: Open
Project: MariaDB Server
Component/s: None
Fix Version/s: None

Type: Task Priority: Major
Reporter: Roman Assignee: Sergei Golubchik
Resolution: Unresolved Votes: 0
Labels: smart_engine

Issue Links:
Relates
relates to MDEV-23860 Move all optimization query re-writes... Closed

 Description   

As of 10.5 Columnstore doesn't tolerate a number of optimizations/rewrites MDB applies to the query:

  • derived table merge optimization
  • conversion of IN + long list of literals into a single-column temp table

We need methods to explicitly disable this rewrites/optimizations for Select Handler execution path.

 Comments   
Comment by Sergei Petrunia [ 2020-09-24 ]

Is this just about the SELECT handler? If yes, I think the optimizations should not be disabled altogether, but rather moved to be applied after the Select Handler execution is tried.

if (try_using_select_handler() == OK)  {
 
  // get the query result from it
 
} else {
 
  // Fall back to regular execution
 
 // Apply all of the optimizations/rewrites.
 
}

Comment by Roman [ 2020-12-01 ]

Not exactly. For example both of the rewrites mentioned affect Derived Handler also.

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