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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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38
sql/opt_hints.h
View File

@@ -51,6 +51,11 @@
each table, as a result TABLE_LIST::opt_hints_table points to the table's
hints.
Non-index hints may be fixed before TABLE instances are available, by
calling fix_hints_for_derived_table and using a TABLE_LIST instance; as
the name implies, this is the case for derived tables (and such tables
are the only use case at this point).
== Hint hierarchy ==
Hints have this hierarchy, less specific to more specific:
@@ -178,6 +183,13 @@ protected:
for key level.
*/
Lex_ident_sys name;
/*
Hints by default are NOT_FIXED.
When hints are fixed, during hint resolution, they
transition from NOT_FIXED to FIXED.
*/
enum class Fixed_state { NOT_FIXED, FIXED };
private:
/*
Parent object. There is no parent for global level,
@@ -193,8 +205,8 @@ private:
/* Array of child objects. i.e. array of the lower level objects */
Mem_root_array<Opt_hints*, true> child_array;
/* true if hint is connected to the real object */
bool fixed;
/* FIXED if hint is connected to the real object (see above) */
Fixed_state fixed;
/*
Number of child hints that are fully fixed, that is, fixed and
@@ -208,7 +220,7 @@ public:
Opt_hints *parent_arg,
MEM_ROOT *mem_root_arg)
: name(name_arg), parent(parent_arg), child_array(mem_root_arg),
fixed(false), n_fully_fixed_children(0)
fixed(Fixed_state::NOT_FIXED), n_fully_fixed_children(0)
{ }
bool is_specified(opt_hints_enum type_arg) const
@@ -260,8 +272,8 @@ public:
}
void set_name(const Lex_ident_sys &name_arg) { name= name_arg; }
Opt_hints *get_parent() const { return parent; }
void set_fixed() { fixed= true; }
bool is_fixed() const { return fixed; }
void set_fixed() { fixed= Fixed_state::FIXED; }
bool is_fixed() const { return fixed == Fixed_state::FIXED; }
void incr_fully_fixed_children() { n_fully_fixed_children++; }
Mem_root_array<Opt_hints*, true> *child_array_ptr() { return &child_array; }
@@ -450,6 +462,8 @@ public:
void append_hint_arguments(THD *thd, opt_hints_enum hint,
String *str) override;
void fix_hints_for_derived_table(TABLE_LIST *table_list);
/**
Function finds Opt_hints_table object corresponding to
table alias in the query block and attaches corresponding
@@ -662,6 +676,20 @@ bool hint_key_state(const THD *thd, const TABLE *table,
uint keyno, opt_hints_enum type_arg,
uint optimizer_switch);
/**
Returns table hint value if hint is specified, returns
fallback value if hint is not specified.
@param thd Pointer to THD object
@param table_lsit Pointer to TABLE_LIST object
@param type_arg Hint type
@param fallback_value Value to be returned if the hint is not set
@return table hint value if hint is specified,
otherwise fallback value.
*/
bool hint_table_state(const THD *thd, const TABLE_LIST *table_list,
opt_hints_enum type_arg, bool fallback_value);
/**
Returns table hint value if hint is specified, returns