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MDEV-17096 Pushdown of simple derived tables to storage engines

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MDEV-17631 select_handler for a full query pushdown

Added comments and file headers for files introduced in these tasks.
This commit is contained in:
Igor Babaev
2019-02-12 22:56:24 -08:00
parent 17d00d9a94
commit 27c3abde30
9 changed files with 223 additions and 15 deletions
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26
sql/sql_select.cc
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@ -1444,7 +1444,10 @@ int JOIN::optimize()
if (select_lex->pushdown_select)
{
if (!(select_options & SELECT_DESCRIBE))
{
/* Prepare to execute the query pushed into a foreign engine */
res= select_lex->pushdown_select->init();
}
with_two_phase_optimization= false;
}
else if (optimization_state == JOIN::OPTIMIZATION_PHASE_1_DONE)
@ -4074,6 +4077,7 @@ void JOIN::exec_inner()
}
else if (select_lex->pushdown_select)
{
/* Execute the query pushed into a foreign engine */
error= select_lex->pushdown_select->execute();
DBUG_VOID_RETURN;
}
@ -4288,9 +4292,11 @@ mysql_select(THD *thd,
}
}
/* Look for a table owned by an engine with the select_handler interface */
select_lex->select_h= select_lex->find_select_handler(thd);
if (select_lex->select_h)
{
/* Create a Pushdown_select object for later execution of the query */
if (!(select_lex->pushdown_select=
new (thd->mem_root) Pushdown_select(select_lex,
select_lex->select_h)))
@ -27620,6 +27626,26 @@ Item *remove_pushed_top_conjuncts(THD *thd, Item *cond)
return cond;
}
/**
@brief
Look for provision of the select_handler interface by a foreign engine
@param thd The thread handler
@details
The function checks that this is an upper level select and if so looks
through its tables searching for one whose handlerton owns a
create_select call-back function. If the call of this function returns
a select_handler interface object then the server will push the select
query into this engine.
This is a responsibility of the create_select call-back function to
check whether the engine can execute the query.
@retval the found select_handler if the search is successful
0 otherwise
*/
select_handler *SELECT_LEX::find_select_handler(THD *thd)
{
if (next_select())