MDEV-38045: Implement QB_NAME hint with path syntax for nested query blocks

Extended QB_NAME hint to support path-based addressing of query blocks
nested within views, derived tables, and CTEs, following TiDB's syntax.

New syntax:
  QB_NAME(name, query_block_path), where
    query_block_path ::= query_block_path_element
                         [ {, query_block_path_element }... ]
    query_block_path_element ::= @ qb_path_element_select_num |
                                   qb_path_element_view_sel
    qb_path_element_view_sel ::= qb_path_element_view_name
                                 [ @ qb_path_element_select_num ]

For example,
  `SELECT /*+ qb_name(qb_v1, v1) */* FROM v1`
The name `qb_v1` is assigned to the inner query block of the view `v1`.

  `SELECT /*+ qb_name(qb_v1, v1@sel_1) */* FROM v1`
Means the same but specifies that `v1` is present in SELECT#1 of the current
query block.

  `SELECT /*+ qb_name(qb_v1, v1@sel_1 .@sel_2) */* FROM v1`
This means SELECT#2 of view `v1`, which is present in SELECT#1 of
the current query block, gets the name `qb_v1`.

It is possible to specify not only view names but also derived tables
and CTE's in the path.

Views and derived tables may be nested on multiple levels, for example:
  `SELECT /*+ qb_name(dt2_dt1_v1_1, dt1 .dt2 .v2 .@SEL_2)
              no_index(t1@dt2_dt1_v1_1)*/ v1.*
  FROM v1 JOIN (SELECT v1.* FROM v1 JOIN (SELECT * FROM v2) dt2) dt1`

Author: Olernov

mysql-test/main/opt_hints_qb_name_path.inc

@@ -0,0 +1,244 @@
+--echo # ======================================
+--echo # Views
+--echo #
+--echo # select /* The name of the current query block is @SEL_1 */ * from v1;
+--echo #
+--echo # Addressing a view having one query block.
+--echo # QB_NAME(qb_v1, v1) means: inner query block of the view `v1`,
+--echo # which is present in the same query block as the hint, gets the name `qb_v1`.
+--echo # This name can be used in other hints.
+explain extended
+  select /*+ qb_name(qb_v1, v1) no_index(t1@qb_v1)*/* from v1;
+
+--echo # Equivalent to the above but specifying @SEL_1 explicitly.
+--echo # QB_NAME(qb_v1, v1@sel_1) means: inner query block of view `v1`,
+--echo # which is present in SELECT#1 of the current query block, gets the name `qb_v1`.
+explain extended
+  select /*+ qb_name(qb_v1, v1@sel_1) no_index(t1@qb_v1 idx_a)*/* from v1;
+
+--echo # Equivalent to the above but also specifying @SEL_1 of the view.
+--echo # QB_NAME(qb_v1, v1@sel_1 .@sel_1) means: SELECT#1 of view `v1`,
+--echo # which is present in SELECT#1 of the current query block, gets the name `qb_v1`.
+explain extended
+  select /*+ qb_name(qb_v1, v1@sel_1 .@sel_1) no_index(t1@qb_v1 idx_ab)*/* from v1;
+
+--echo #
+--echo # The case when a particular view is used in more than one query block.
+--echo #   select /* Name of current query block is @SEL_1 */ * from v1
+--echo #   join
+--echo #   (select /* Name of current query block is @SEL_2 */ * from v1) vvv1;
+--echo # The first query block of view v1 can be declared as
+--echo #   QB_NAME(v1_1, v1@SEL_1 .@SEL_1),
+--echo # and the second query block of the view v1 can be declared as
+--echo #   QB_NAME(v1_2, v1@SEL_1 .@SEL_2).
+--echo #
+--echo # By default, range access is used for both `t1`'s in the statement below. 
+explain extended
+  select * from v1 join (select * from v1) vvv1;
+
+--echo # Disable index access for t1 from the second occurence of view v1:
+explain extended
+  select /*+ qb_name(v1_2, v1@SEL_2 .@SEL_1) no_index(t1@v1_2)*/ *
+    from v1 join (select * from v1) vvv1;
+
+--echo # Disable index access for t1 from both occurences of view v1:
+explain extended
+  select /*+ qb_name(v1_1, v1@SEL_1) qb_name(v1_2, v1@SEL_2 .@SEL_1)
+      no_index(t1@v1_1) no_index(t1@v1_2)*/ *
+    from v1 join (select * from v1) vvv1;
+
+--echo #
+--echo # The case when a particular view has more than one query block.
+--echo # create view v2 as
+--echo #   select * from t1 join /* Name of this query block is @SEL_1 */
+--echo #   (
+--echo #     select count(*) from t1 join v1 /* Name of this query block is @SEL_2 */
+--echo #   ) tt;
+--echo # The first query block of view v2 can be declared as
+--echo # QB_NAME(v2_1, v2@SEL_1 .@SEL_1), and the second query block can be
+--echo # declared as QB_NAME(v2_2, v2@SEL_1 .@SEL_2).
+--echo #
+--echo # See the default execution plan:
+explain extended select * from v2;
+
+--echo # Disable index access for t1 from the second query block of view v2:
+explain extended
+  select /*+ qb_name(v2_2, v2@SEL_1 .@SEL_2) no_index(t1@v2_2)*/* from v2;
+
+--echo # Disable index access for `t1` from view `v1` used in
+--echo # the first query block of view `v2`:
+explain extended
+  select /*+ qb_name(v2_v1, v2@SEL_1 .v1@SEL_2) no_index(t1@v2_v1)*/* from v2;
+
+--echo # Equivalent to the above but specifying @SEL_1 explicitly:
+explain extended
+  select /*+ qb_name(v2_v1_sel1, v2@SEL_1 .v1@SEL_2 .@SEL_1)
+             no_index(t1@v2_v1_sel1)*/ * from v2;
+
+--echo # Disable index access for `t1` tables from views `v1` and `v2`
+explain extended
+  select /*+ qb_name(v2_v1, v2@SEL_1 .v1@SEL_2) no_index(t1@v2_v1)
+             qb_name(v2_2, v2@SEL_1 .@SEL_2) no_index(t1@v2_2) */ * from v2;
+
+--echo # ======================================
+--echo # Views with UNION
+--echo #
+--echo # Default execution plan:
+explain extended select * from v3;
+
+--echo # `v3` in QB path corresponds to @SEL_1:
+explain extended select /*+ qb_name(qb_v3, v3) no_index(t1@qb_v3)*/* from v3;
+
+--echo # Addressing @SEL_1 of `v3` explicitly:
+explain extended
+  select /*+ qb_name(qb_v3_sel1, v3.@sel_1) no_index(t1@qb_v3_sel1)*/* from v3;
+
+--echo # Addressing @SEL_2 of `v3` explicitly:
+explain extended
+  select /*+ qb_name(qb_v3_sel2, v3.@sel_2) no_index(t1@qb_v3_sel2)*/* from v3;
+
+
+--echo # ======================================
+--echo # Derived tables
+--echo #
+--echo # QB_NAME(qb_dt, dt) means: inner query block of derived table `dt`,
+--echo # which is present in the same query block as the hint, gets the name `qb_dt`.
+--echo # This name can be used in other hints.
+explain extended select /*+ qb_name(qb_dt, dt) no_index(t1@qb_dt)*/* from
+  (select * from t1 where a < 10) dt;
+
+--echo # QB_NAME(qb_dt, dt@sel_1) means: inner query block of derived table `dt`,
+--echo # which is present in SELECT#1 of the current query block, gets the name `qb_dt`.
+explain extended select /*+ qb_name(qb_dt, dt@sel_1) no_index(t1@qb_dt)*/* from
+  (select * from t1 where a < 10) dt;
+
+--echo # QB_NAME(qb_dt, dt@sel_1 .@sel_1) means: SELECT#1 of derived table `dt`,
+--echo # which is present in SELECT#1 of the current query block, gets the name `qb_dt`.
+explain extended select /*+ qb_name(qb_dt, dt@sel_1 .@sel_1) no_index(t1@qb_dt)*/* from
+  (select * from t1 where a < 10) dt;
+
+--echo # ======================================
+--echo # Derived tables with UNION
+--echo #
+--echo # Default execution plan:
+explain extended
+select * from (select * from t1 where a < 10 union select * from t1 where a > 90) dt;
+
+--echo # `dt` in QB path corresponds to @SEL_1:
+explain extended
+select /*+ qb_name(qb_dt, dt) no_index(t1@qb_dt)*/* from
+  (select * from t1 where a < 10 union select * from t1 where a > 90) dt;
+
+--echo # Addressing @SEL_1 of `dt` explicitly:
+explain extended
+select /*+ qb_name(qb_dt_sel1, dt.@sel_1) no_index(t1@qb_dt_sel1)*/* from
+  (select * from t1 where a < 10 union select * from t1 where a > 90) dt;
+
+--echo # Addressing @SEL_2 of `dt` explicitly:
+explain extended
+select /*+ qb_name(qb_dt_sel2, dt.@sel_2) no_index(t1@qb_dt_sel2)*/* from
+  (select * from t1 where a < 10 union select * from t1 where a > 90) dt;
+
+--echo # ======================================
+--echo # Mix of views and derived tables
+--echo #
+explain extended
+select /*+ qb_name(dt1_v1_1, dt1 .v1 .@SEL_1) no_index(t1@dt1_v1_1)*/ *
+  from v1 join (select * from v1) dt1;
+
+--echo # More complicated query. Default execution plan:
+explain extended
+select v1.* from v1 join (select v1.* from v1 join (select * from v2) dt2) dt1;
+
+explain extended
+select /*+ qb_name(dt1_v1_1, dt1 .v1 .@SEL_1) no_index(t1@dt1_v1_1)*/ v1.*
+  from v1 join (select v1.* from v1 join (select * from v2) dt2) dt1;
+
+explain extended
+select /*+ qb_name(dt2_dt1_v1_1, dt1 .dt2 .v2 .@SEL_2)
+           no_index(t1@dt2_dt1_v1_1)*/ v1.*
+  from v1 join (select v1.* from v1 join (select * from v2) dt2) dt1;
+
+--echo # ======================================
+--echo # CTEs
+--echo #
+--echo # Default execution plan:
+explain extended
+with cte as (select count(*) from t1, (select * from t1 where a < 5) dt1)
+select * from cte;
+
+--echo # Disable index access for t1 in CTE
+explain extended
+with cte as (select count(*) from t1, (select * from t1 where a < 5) dt1)
+select /*+ qb_name(qb_cte, cte) no_index(t1@qb_cte)*/ * from cte;
+
+--echo # Disable index access for t1 in dt1 of CTE
+explain extended
+with cte as (select count(*) from t1, (select * from t1 where a < 5) dt1)
+select /*+ qb_name(qb_cte_dt1, cte .dt1) no_index(t1@qb_cte_dt1)*/ * from cte;
+
+--echo # Disable index access for both t1's
+explain extended
+with cte as (select count(*) from t1, (select * from t1 where a < 5) dt1)
+select /*+ qb_name(qb_cte, cte) no_index(t1@qb_cte)
+           qb_name(qb_cte_dt1, cte .dt1) no_index(t1@qb_cte_dt1)*/ * from cte;
+
+--echo # Multiple references to a CTE in a query.
+--echo # Default execution plan:
+explain extended
+with cte as (select count(*) from t1, (select * from t1 where a < 5) dt1)
+select * from cte join cte cte1;
+
+--echo # Disable index access for t1 in `cte`
+explain extended
+with cte as (select count(*) from t1, (select * from t1 where a < 5) dt1)
+select /*+ qb_name(qb_cte, cte) no_index(t1@qb_cte)*/ * from cte join cte as cte1;
+
+--echo # Disable index access for t1 in `cte1`
+explain extended
+with cte as (select count(*) from t1, (select * from t1 where a < 5) dt1)
+select /*+ qb_name(qb_cte1, cte1) no_index(t1@qb_cte1)*/ * from cte join cte as cte1;
+
+
+--echo # ======================================
+--echo # Wrong paths generate warnings
+--echo #
+--disable_ps_protocol
+# PS protocol is disabled because the warning is genererated only during
+# PREPARE step of a statement. When the QB name cannot be resolved the hint
+# is discarded, so it is not present during EXECUTE step.
+
+explain extended
+  select /*+ qb_name(`qb_v1`, `v2`)*/* from v1;
+
+--echo # Wrong select number:
+explain extended
+  select /*+ qb_name(qb_v1, `v2`@`sel_2`)*/* from v1;
+
+explain extended
+  select /*+ qb_name(qb_v1, v2@sel_1 .@sel_2)*/* from v1;
+
+--echo # Attempting to reference a regular table as a query block:
+explain extended
+  select /*+ qb_name(qb_v1, dt .t1)*/* from (select t1.* from t1 join v1) dt;
+
+--echo # Wrong view name inside a derived table:
+explain extended
+  select /*+ qb_name(qb_v1, dt .v2)*/* from (select t1.* from t1 join v1) dt;
+
+--echo # Wrong select number:
+explain extended
+select /*+ qb_name(qb_v1, dt .v1@sel_2)*/* from (select t1.* from t1 join v1) dt;
+
+explain extended
+select /*+ qb_name(qb_v1, dt .v1@sel_1 .@sel_2)*/* from
+  (select t1.* from t1 join v1) dt;
+
+--echo # Wrong select number syntax:
+explain extended
+  select /*+ qb_name(qb_v1, `v1`@`lex_2`)*/* from v1;
+
+explain extended
+  select /*+ qb_name(qb_v1, v1 .lex_2)*/* from v1;
+
+--enable_ps_protocol