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MDEV-36106 New-style hints: [NO_]DERIVED_CONDITION_PUSHDOWN, [NO_]MERGE

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Implements and tests the optimizer hints DERIVED_CONDITION_PUSHDOWN
and NO_DERIVED_CONDITION_PUSHDOWN, table-level hints to enable and
disable, respectively, the condition pushdown for derived tables
which is typically controlled by the condition_pushdown_for_derived
optimizer switch.

Implements and tests the optimizer hints MERGE and NO_MERGE, table-level
hints to enable and disable, respectively, the derived_merge optimization
which is typically controlled by the derived_merge optimizer switch.

Sometimes hints need to be fixed before TABLE instances are available, but
after TABLE_LIST instances have been created (as in the cases of MERGE and
NO_MERGE).  This commit introduces a new function called
fix_hints_for_derived_table to allow early hint fixing for derived tables,
using only a TABLE_LIST instance (so long as such hints are not index-level).
This commit is contained in:
Dave Gosselin
2025-02-24 11:32:27 -05:00
committed by Dave Gosselin
parent e653666368
commit 2ee2e2d0f3
10 changed files with 3367 additions and 41 deletions
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62
sql/opt_hints.cc
View File

@@ -45,6 +45,8 @@ struct st_opt_hint_info opt_hint_info[]=
{{STRING_WITH_LEN("JOIN_SUFFIX")}, false, true, true},
{{STRING_WITH_LEN("JOIN_ORDER")}, false, true, true},
{{STRING_WITH_LEN("JOIN_FIXED_ORDER")}, false, true, false},
{{STRING_WITH_LEN("DERIVED_CONDITION_PUSHDOWN")}, false, false, false},
{{STRING_WITH_LEN("MERGE")}, false, false, false},
{null_clex_str, 0, 0, 0}
};
@@ -199,6 +201,7 @@ Opt_hints_qb *get_qb_hints(Parse_context *pc)
/*
Mark the query block as resolved as we know which SELECT_LEX it is
attached to.
Note that children (indexes, tables) are probably not resolved, yet.
*/
qb->set_fixed();
@@ -398,10 +401,52 @@ Opt_hints_qb::Opt_hints_qb(Opt_hints *opt_hints_arg,
}
/**
fix_hints_for_derived_table allows early hint fixing for
derived tables by linking both *this and the Opt_hints_table
object to the passed TABLE_LIST instance.
@param table_list Pointer to TABLE_LIST object
*/
void Opt_hints_qb::fix_hints_for_derived_table(TABLE_LIST *table_list)
{
Opt_hints_table *tab=
static_cast<Opt_hints_table *>(find_by_name(table_list->alias));
/*
If this is fixed and the corresponding Opt_hints_table doesn't exist (or it
exists and is fixed) then there's nothing to do, so return early.
*/
if (is_fixed() && (!tab || tab->is_fixed()))
return;
/*
This instance will have been marked as fixed on the basis of its
attachment to a SELECT_LEX (during get_qb_hints) but that is
insufficient to consider it fixed for the case where a TABLE
instance is required but not yet available. If the associated
table isn't yet fixed, then fix this hint as though it were unfixed.
We mark the Opt_hints_table as 'fixed' here and this means we
won't try to fix the child hints again later. They will remain
unfixed and will eventually produce "Unresolved index name" error
in opt_hints_qb->check_unfixed(). This is acceptable because
no child hints apply to derived tables.
*/
DBUG_ASSERT(!table_list->opt_hints_table);
DBUG_ASSERT(tab);
table_list->opt_hints_qb= this;
table_list->opt_hints_table= tab;
tab->set_fixed();
}
Opt_hints_table *Opt_hints_qb::fix_hints_for_table(TABLE *table,
const Lex_ident_table &alias)
{
Opt_hints_table *tab= static_cast<Opt_hints_table *>(find_by_name(alias));
Opt_hints_table *tab=
static_cast<Opt_hints_table *>(find_by_name(alias));
table->pos_in_table_list->opt_hints_qb= this;
@@ -591,11 +636,9 @@ bool hint_key_state(const THD *thd, const TABLE *table,
}
bool hint_table_state(const THD *thd, const TABLE *table,
opt_hints_enum type_arg,
bool fallback_value)
bool hint_table_state(const THD *thd, const TABLE_LIST *table_list,
opt_hints_enum type_arg, bool fallback_value)
{
TABLE_LIST *table_list= table->pos_in_table_list;
if (table_list->opt_hints_qb)
{
bool ret_val= false;
@@ -609,6 +652,15 @@ bool hint_table_state(const THD *thd, const TABLE *table,
}
bool hint_table_state(const THD *thd, const TABLE *table,
opt_hints_enum type_arg,
bool fallback_value)
{
return hint_table_state(thd, table->pos_in_table_list, type_arg,
fallback_value);
}
void append_table_name(THD *thd, String *str, const LEX_CSTRING &table_name,
const LEX_CSTRING &qb_name)
{