From 96debea33e3b3b462be50b1630debdbe073a49da Mon Sep 17 00:00:00 2001
From: Andres Taylor <andres@planetscale.com>
Date: Mon, 6 Nov 2023 14:29:18 +0100
Subject: [PATCH] wip

---
 go/vt/vtgate/engine/opcode/constants.go      |  6 ++++-
 go/vt/vtgate/planbuilder/operators/phases.go | 24 ++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/go/vt/vtgate/engine/opcode/constants.go b/go/vt/vtgate/engine/opcode/constants.go
index 07a39020f8b..af0959eef53 100644
--- a/go/vt/vtgate/engine/opcode/constants.go
+++ b/go/vt/vtgate/engine/opcode/constants.go
@@ -74,6 +74,7 @@ const (
 	AggregateAnyValue
 	AggregateCountStar
 	AggregateGroupConcat
+	AggregateAvg
 	_NumOfOpCodes // This line must be last of the opcodes!
 )
 
@@ -85,6 +86,7 @@ var (
 		AggregateCountStar:     sqltypes.Int64,
 		AggregateSumDistinct:   sqltypes.Decimal,
 		AggregateSum:           sqltypes.Decimal,
+		AggregateAvg:           sqltypes.Decimal,
 		AggregateGtid:          sqltypes.VarChar,
 	}
 )
@@ -96,6 +98,7 @@ var SupportedAggregates = map[string]AggregateOpcode{
 	"sum":   AggregateSum,
 	"min":   AggregateMin,
 	"max":   AggregateMax,
+	"avg":   AggregateAvg,
 	// These functions don't exist in mysql, but are used
 	// to display the plan.
 	"count_distinct": AggregateCountDistinct,
@@ -117,6 +120,7 @@ var AggregateName = map[AggregateOpcode]string{
 	AggregateCountStar:     "count_star",
 	AggregateGroupConcat:   "group_concat",
 	AggregateAnyValue:      "any_value",
+	AggregateAvg:           "avg",
 }
 
 func (code AggregateOpcode) String() string {
@@ -145,7 +149,7 @@ func (code AggregateOpcode) Type(typ querypb.Type) querypb.Type {
 		return sqltypes.Text
 	case AggregateMax, AggregateMin, AggregateAnyValue:
 		return typ
-	case AggregateSumDistinct, AggregateSum:
+	case AggregateSumDistinct, AggregateSum, AggregateAvg:
 		if sqltypes.IsIntegral(typ) || sqltypes.IsDecimal(typ) {
 			return sqltypes.Decimal
 		}
diff --git a/go/vt/vtgate/planbuilder/operators/phases.go b/go/vt/vtgate/planbuilder/operators/phases.go
index 80f5ce71512..a09e09f973b 100644
--- a/go/vt/vtgate/planbuilder/operators/phases.go
+++ b/go/vt/vtgate/planbuilder/operators/phases.go
@@ -19,6 +19,7 @@ package operators
 import (
 	"vitess.io/vitess/go/slice"
 	"vitess.io/vitess/go/vt/sqlparser"
+	"vitess.io/vitess/go/vt/vtgate/engine/opcode"
 	"vitess.io/vitess/go/vt/vtgate/planbuilder/operators/ops"
 	"vitess.io/vitess/go/vt/vtgate/planbuilder/operators/rewrite"
 	"vitess.io/vitess/go/vt/vtgate/planbuilder/plancontext"
@@ -140,12 +141,35 @@ func addOrderingForAllAggregations(ctx *plancontext.PlanningContext, root ops.Op
 			res = rewrite.NewTree("added ordering before aggregation", in)
 		}
 
+		if needAvgBreaking(aggrOp.Aggregations) {
+			return splitAvgAggregations()
+		}
+
+		for _, aggr := range aggrOp.Aggregations {
+			if aggr.OpCode == opcode.AggregateAvg {
+
+			}
+		}
+
 		return in, res, nil
 	}
 
 	return rewrite.BottomUp(root, TableID, visitor, stopAtRoute)
 }
 
+func needAvgBreaking(aggrs []Aggr) bool {
+	for _, aggr := range aggrs {
+		if aggr.OpCode == opcode.AggregateAvg {
+			return true
+		}
+	}
+	return false
+}
+
+func splitAvgAggregations() {
+
+}
+
 func addOrderingFor(aggrOp *Aggregator) {
 	orderBys := slice.Map(aggrOp.Grouping, func(from GroupBy) ops.OrderBy {
 		return from.AsOrderBy()