wip

_posts/2024/2024-05-13-tidb-join.md

@@ -1,6 +1,6 @@
 ---
 layout: post
-title: "How does TiDB translate JOIN into logical plans"
+title: "How does TiDB translate JOIN and GROUP BY into logical plans"
 description: "" 
 category: 
 tags: [tidb, golang]
@@ -61,3 +61,34 @@ func (b *planBuilder) buildJoin(join *ast.Join) LogicalPlan {
 ```
 
 
+```go
+
+// AggFuncDesc describes an aggregation function signature, only used in planner.
+type AggFuncDesc struct {
+	// Name represents the aggregation function name.
+	Name string
+	// Args represents the arguments of the aggregation function.
+	Args []expression.Expression
+	// RetTp represents the return type of the aggregation function.
+	RetTp *types.FieldType
+	// Mode represents the execution mode of the aggregation function.
+	Mode AggFunctionMode
+	// HasDistinct represents whether the aggregation function contains distinct attribute.
+	HasDistinct bool
+}
+
+// LogicalAggregation represents an aggregate plan.
+type LogicalAggregation struct {
+	logicalSchemaProducer
+
+	AggFuncs     []*aggregation.AggFuncDesc
+	GroupByItems []expression.Expression
+	// groupByCols stores the columns that are group-by items.
+	groupByCols []*expression.Column
+
+	possibleProperties [][]*expression.Column
+	inputCount         float64 // inputCount is the input count of this plan.
+}
+
+```
+