planner: fix uninitialized stats for expression index (#63961)

[ti-chi-bot]

This is an automated cherry-pick of #63961

What problem does this PR solve?

Issue Number: close #57090

Problem Summary:

For the following case, the explain analyze output shows unInitialized for that expression index(idx_expr), which is confusing.

set @@global.tidb_enable_auto_analyze = 'OFF';
drop table if exists t1;
-- This is required to make sure the expression collation is same when creating table and using it in select stmt.
set names utf8mb4;
create table t1(id int, c1 int, c2 varchar(100), primary key(id), key idx_expr ((cast(json_unquote(json_extract(`c2`, _utf8mb4'$.location_id')) as char(255)) collate utf8mb4_bin)));
insert into t1 values(1, 1, '{"foo": "bar"}'), (2, 1, '{"foo": "bar"}');
analyze table t1 all columns;
-- You may need to run multiple times to trigger load stats
explain analyze select /*+ use_index(t1, idx_expr) */ * from t1 where (cast(json_unquote(json_extract(`c2`, _utf8mb4'$.location_id')) as char(255)) collate utf8mb4_bin) > '100'  and c2 > 'abc';

TiDB [email protected]:test> explain analyze select /*+ use_index(t1, idx_expr) */ * from t1 where (cast(json_unquote(json_extract(`c2`, _utf8mb4'$.location_id')) as char(255)) collate utf8mb4_bin) > '100'  and c2 > 'abc';
+-----------------------------+---------+---------+-----------+----------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------+-----------+------+
| id                          | estRows | actRows | task      | access object                                                                                                              | execution info                                                                                                                                                                                                                                                                                 | operator info                                                                     | memory    | disk |
+-----------------------------+---------+---------+-----------+----------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------+-----------+------+
| Projection_4                | 1.00    | 0       | root      |                                                                                                                            | time:631.5µs, open:72.2µs, close:10.5µs, loops:1, RU:0.48, Concurrency:OFF                                                                                                                                                                                                                     | test.t1.id, test.t1.c1, test.t1.c2                                                | 10.1 KB   | N/A  |
| └─IndexLookUp_10            | 1.00    | 0       | root      |                                                                                                                            | time:614.3µs, open:62µs, close:7.71µs, loops:1                                                                                                                                                                                                                                                 |                                                                                   | 182 Bytes | N/A  |
|   ├─IndexRangeScan_7(Build) | 1.00    | 0       | cop[tikv] | table:t1, index:idx_expr(cast(json_unquote(json_extract(`c2`, _utf8mb4'$.location_id')) as char(255)) collate utf8mb4_bin) | time:410.6µs, open:0s, close:0s, loops:1, cop_task: {num: 1, max: 343.8µs, proc_keys: 0, copr_cache_hit_ratio: 0.00, build_task_duration: 20.8µs, max_distsql_concurrency: 1}, fetch_resp_duration: 384.4µs, rpc_info:{Cop:{num_rpc:1, total_time:297.6µs}}, tikv_task:{time:185.4µs, loops:0} | range:("100",+inf], keep order:false, stats:partial[_v$_idx_expr_0:unInitialized] | N/A       | N/A  |
|   └─Selection_9(Probe)      | 1.00    | 0       | cop[tikv] |                                                                                                                            |                                                                                                                                                                                                                                                                                                | gt(test.t1.c2, "abc")                                                             | N/A       | N/A  |
|     └─TableRowIDScan_8      | 1.00    | 0       | cop[tikv] | table:t1                                                                                                                   |                                                                                                                                                                                                                                                                                                | keep order:false, stats:partial[_v$_idx_expr_0:unInitialized]                     | N/A       | N/A  |
+-----------------------------+---------+---------+-----------+----------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------+-----------+------+

For expression index idx_expr, there will be both original column stats and index stats when calculating selectivity.

Check the following debug output, you can see the column stats is unInitialized and the index stats is ready. So for expression index, should use index stats and its column stats.

(dlv) p coll.columns[4].Info
("*github.com/pingcap/tidb/pkg/meta/model.ColumnInfo")(0x14038993ce0)
*github.com/pingcap/tidb/pkg/meta/model.ColumnInfo {
	ID: 4,
	Name: github.com/pingcap/tidb/pkg/parser/ast.CIStr {
		O: "_V$_idx_expr_0",
		L: "_v$_idx_expr_0",},
	Offset: 3,
	OriginDefaultValue: interface {} nil,
	OriginDefaultValueBit: []uint8 len: 0, cap: 0, nil,
	DefaultValue: interface {} nil,
	DefaultValueBit: []uint8 len: 0, cap: 0, nil,
	DefaultIsExpr: false,
	GeneratedExprString: "cast(json_unquote(json_extract(`c2`, _utf8mb4'$.location_id')) a...+32 more",
	GeneratedStored: false,
	Dependences: map[string]struct {} [
		"c2": {},
	],
	FieldType: github.com/pingcap/tidb/pkg/parser/types.FieldType {
		tp: 253,
		flag: 8,
		flen: 255,
		decimal: -1,
		charset: "utf8mb4",
		collate: "utf8mb4_bin",
		elems: []string len: 0, cap: 0, nil,
		elemsIsBinaryLit: []bool len: 0, cap: 0, nil,
		array: false,},
	State: StatePublic (5),
	Comment: "",
	Hidden: true,
	ChangeStateInfo: *github.com/pingcap/tidb/pkg/meta/model.ChangeStateInfo nil,
	Version: 2,}
(dlv) p coll.columns[4].StatsLoadedStatus
github.com/pingcap/tidb/pkg/statistics.StatsLoadedStatus {statsInitialized: false, evictedStatus: 0}

(dlv) p coll.indices[1].Info
("*github.com/pingcap/tidb/pkg/meta/model.IndexInfo")(0x140389c0f00)
*github.com/pingcap/tidb/pkg/meta/model.IndexInfo {
	ID: 1,
	Name: github.com/pingcap/tidb/pkg/parser/ast.CIStr {
		O: "idx_expr",
		L: "idx_expr",},
	Table: github.com/pingcap/tidb/pkg/parser/ast.CIStr {O: "", L: ""},
	Columns: []*github.com/pingcap/tidb/pkg/meta/model.IndexColumn len: 1, cap: 1, [
		*(*"github.com/pingcap/tidb/pkg/meta/model.IndexColumn")(0x14038b5c4e0),
	],
	State: StatePublic (5),
	BackfillState: BackfillStateInapplicable (0),
	Comment: "",
	Tp: IndexTypeBtree (1),
	Unique: false,
	Primary: false,
	Invisible: false,
	Global: false,
	MVIndex: false,
	VectorInfo: *github.com/pingcap/tidb/pkg/meta/model.VectorIndexInfo nil,
	InvertedInfo: *github.com/pingcap/tidb/pkg/meta/model.InvertedIndexInfo nil,
	FullTextInfo: *github.com/pingcap/tidb/pkg/meta/model.FullTextIndexInfo nil,}
(dlv) p coll.indices[1].StatsLoadedStatus
github.com/pingcap/tidb/pkg/statistics.StatsLoadedStatus {statsInitialized: true, evictedStatus: 0}

What changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

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