planner: rewrite LIKE as range for expression index (#24250)

pingcap · May 24, 2021 · 23ce657 · 23ce657
1 parent 9d8935e
commit 23ce657
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diff --git a/cmd/explaintest/r/explain_generate_column_substitute.result b/cmd/explaintest/r/explain_generate_column_substitute.result
@@ -389,3 +389,28 @@ explain format = 'brief' select c0 from t0;
 id	estRows	task	access object	operator info
 TableReader	10000.00	root		data:TableFullScan
 └─TableFullScan	10000.00	cop[tikv]	table:t0	keep order:false, stats:pseudo
+ -- TableRead
+drop table if exists tbl1;
+create table tbl1 (id int unsigned not null auto_increment primary key, s int, index((md5(s))));
+insert into tbl1 (id) select null;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+ insert into tbl1 (id) select null from tbl1;
+update tbl1 set s=id%32;
+explain format = 'brief' select count(*) from tbl1 where md5(s) like '02e74f10e0327ad868d138f2b4fdd6f%';
+id	estRows	task	access object	operator info
+StreamAgg	1.00	root		funcs:count(Column#6)->Column#4
+└─IndexReader	1.00	root		index:StreamAgg
+  └─StreamAgg	1.00	cop[tikv]		funcs:count(1)->Column#6
+    └─IndexRangeScan	250.00	cop[tikv]	table:tbl1, index:expression_index(md5(`s`))	range:["02e74f10e0327ad868d138f2b4fdd6f","02e74f10e0327ad868d138f2b4fdd6g"), keep order:false, stats:pseudo
+select count(*) from tbl1 use index() where md5(s) like '02e74f10e0327ad868d138f2b4fdd6f%';
+count(*)
+64
diff --git a/cmd/explaintest/t/explain_generate_column_substitute.test b/cmd/explaintest/t/explain_generate_column_substitute.test
@@ -174,3 +174,11 @@ explain format = 'brief' select c0 from t0; -- TableRead
 drop table if exists t0;
 create table t0(c0 double, c1 float as (c0) unique);
 explain format = 'brief' select c0 from t0; -- TableRead
+
+drop table if exists tbl1;
+create table tbl1 (id int unsigned not null auto_increment primary key, s int, index((md5(s))));
+insert into tbl1 (id) select null; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1; insert into tbl1 (id) select null from tbl1;
+update tbl1 set s=id%32;
+explain format = 'brief' select count(*) from tbl1 where md5(s) like '02e74f10e0327ad868d138f2b4fdd6f%';
+select count(*) from tbl1 use index() where md5(s) like '02e74f10e0327ad868d138f2b4fdd6f%';
+
diff --git a/planner/core/rule_generate_column_substitute.go b/planner/core/rule_generate_column_substitute.go
@@ -119,6 +119,12 @@ func (gc *gcSubstituter) substitute(ctx context.Context, lp LogicalPlan, exprToC
 						tryToSubstituteExpr(expr, lp.SCtx(), candidateExpr, tp, x.Schema(), column)
 					}
 				}
+			case ast.Like:
+				expr := &sf.GetArgs()[0]
+				tp = sf.GetArgs()[1].GetType().EvalType()
+				for candidateExpr, column := range exprToColumn {
+					tryToSubstituteExpr(expr, lp.SCtx(), candidateExpr, tp, x.Schema(), column)
+				}
 			}
 		}
 	case *LogicalProjection: