planner: optimize the performance of GetParamSQLFromAST for non-prep plan cache

planner/core/plan_cache_param.go

@@ -45,6 +45,9 @@ var (
 		restoreCtx := format.NewRestoreCtx(format.RestoreForNonPrepPlanCache|format.RestoreStringWithoutCharset|format.RestoreStringSingleQuotes|format.RestoreNameBackQuotes, buf)
 		return restoreCtx
 	}}
+	paramMakerPool = sync.Pool{New: func() interface{} {
+		return ast.NewParamMarkerExpr(0)
+	}}
 )
 
 // paramReplacer is an ast.Visitor that replaces all values with `?` and collects them.
@@ -72,8 +75,9 @@ func (pr *paramReplacer) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
 		}
 	case *driver.ValueExpr:
 		pr.params = append(pr.params, n)
-		param := ast.NewParamMarkerExpr(len(pr.params) - 1)  // offset is used as order in non-prepared plan cache.
-		n.Datum.Copy(&param.(*driver.ParamMarkerExpr).Datum) // init the ParamMakerExpr's Datum
+		param := paramMakerPool.Get().(*driver.ParamMarkerExpr)
+		param.Offset = len(pr.params) - 1 // offset is used as order in non-prepared plan cache.
+		n.Datum.Copy(&param.Datum)        // init the ParamMakerExpr's Datum
 		return param, true
 	}
 	return in, false
@@ -129,7 +133,9 @@ func (pr *paramRestorer) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
 			return nil, true
 		}
 		// offset is used as order in non-prepared plan cache.
-		return pr.params[n.Offset], true
+		offset := n.Offset
+		paramMakerPool.Put(n)
+		return pr.params[offset], true
 	}
 	if pr.err != nil {
 		return nil, true
@@ -162,6 +168,7 @@ func RestoreASTWithParams(ctx context.Context, _ sessionctx.Context, stmt ast.St
 func Params2Expressions(params []*driver.ValueExpr) []expression.Expression {
 	exprs := make([]expression.Expression, 0, len(params))
 	for _, p := range params {
+		// TODO: add a sync.Pool for type.FieldType and expression.Constant here.
 		tp := new(types.FieldType)
 		types.InferParamTypeFromDatum(&p.Datum, tp)
 		exprs = append(exprs, &expression.Constant{

planner/core/plan_cache_param_test.go

@@ -145,3 +145,15 @@ func BenchmarkParameterizeInsert(b *testing.B) {
 		ParameterizeAST(context.Background(), sctx, stmt)
 	}
 }
+
+func BenchmarkGetParamSQL(b *testing.B) {
+	paymentInsertHistory := `INSERT INTO history (h_c_d_id, h_c_w_id, h_c_id, h_d_id, h_w_id, h_date, h_amount, h_data) VALUES (1, 2, 3, 4, 5, 6, 7, 8)`
+	stmt, err := parser.New().ParseOneStmt(paymentInsertHistory, "", "")
+	require.Nil(b, err)
+	sctx := MockContext()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		GetParamSQLFromAST(context.Background(), sctx, stmt)
+	}
+}