MDEV-38045 Implement QB_NAME hint with path syntax for nested query blocks#4482
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MDEV-38045 Implement QB_NAME hint with path syntax for nested query blocks#4482
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This patch implements support for implicit query block (QB) names in optimizer hints, allowing hints to reference query blocks and tables within derived tables, views and CTEs without requiring explicit QB_NAME hints. Examples. -- Addressing a table inside a derived table using implicit QB name select /*+ no_index(t1@dt) */ * from (select * from t1 where a > 10) as DT; -- this is an equivalent to: select /*+ no_index(t1@dt) */ * from (select /*+ qb_name(dt)*/ * from t1 where a > 10) as DT; -- Addressing a query block corresponding to the derived table select /*+ no_bnl(@dt) */ * from (select * from t1, t2 where t.1.a > t2.a) as DT; -- View create view v1 as select * from t1 where a > 10 and b > 100; -- referencing a table inside a view by implicit QB name: select /*+ index_merge(t1@v1 idx_a, idx_b) */ * from v1, t2 where v1.a = t2.a; -- equivalent to: create view v1 as select /*+ qb_name(qb_v1) */ * from t1 where a > 10 and b > 100; select /*+ index_merge(t1@qb_v1 idx_a, idx_b) */ * from v1, t2 where v1.a = t2.a; -- CTE with aless100 as (select a from t1 where b <100) select /*+ index(t1@aless100) */ * from aless100; -- equivalent to: with aless100 as (select /*+ qb_name(aless100) */ a from t1 where b <100) select /*+ index(t1@aless100) */ * from aless100; Key changes: 1. Two-stage hint resolution - Introduced hint_resolution_stage enum (EARLY/LATE) to control when different hint types are resolved: - EARLY stage: before opening tables (QB_NAME, MERGE hints) - LATE stage: after opening tables (all other hints) 2. Implicit QB name support - Derived table/view/CTE aliases can now be used as implicit query block names in hint syntax: @alias, table@alias - Derived tables inside views can be addressed from outer queries using their aliases
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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`
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Description
This PR follows #4463.
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:
For example,
SELECT /*+ qb_name(qb_v1, v1) */* FROM v1The name
qb_v1is assigned to the inner query block of the viewv1.SELECT /*+ qb_name(qb_v1, v1@sel_1) */* FROM v1Means the same but specifies that
v1is present in SELECT#1 of the currentquery block.
SELECT /*+ qb_name(qb_v1, v1@sel_1 .@sel_2) */* FROM v1This means SELECT#2 of view
v1, which is present in SELECT#1 ofthe 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) dt1How can this PR be tested?
./mtr opt_hints_qb_name_pathBasing the PR against the correct MariaDB version
mainbranch.PR quality check