Improve typing during query planning

go/vt/vtgate/planbuilder/operators/aggregator.go

@@ -379,7 +379,7 @@ func (a *Aggregator) planOffsets(ctx *plancontext.PlanningContext) Operator {
 			a.Grouping[idx].ColOffset = offset
 			gb.ColOffset = offset
 		}
-		if gb.WSOffset != -1 || !ctx.SemTable.NeedsWeightString(gb.Inner) {
+		if gb.WSOffset != -1 || !ctx.NeedsWeightString(gb.Inner) {
 			continue
 		}
 
@@ -508,7 +508,7 @@ func (a *Aggregator) pushRemainingGroupingColumnsAndWeightStrings(ctx *planconte
 			a.Grouping[idx].ColOffset = offset
 		}
 
-		if gb.WSOffset != -1 || !ctx.SemTable.NeedsWeightString(gb.Inner) {
+		if gb.WSOffset != -1 || !ctx.NeedsWeightString(gb.Inner) {
 			continue
 		}
 

go/vt/vtgate/planbuilder/operators/distinct.go

@@ -50,7 +50,7 @@ func (d *Distinct) planOffsets(ctx *plancontext.PlanningContext) Operator {
 	for idx, col := range columns {
 		e := col.Expr
 		var wsCol *int
-		if ctx.SemTable.NeedsWeightString(e) {
+		if ctx.NeedsWeightString(e) {
 			offset := d.Source.AddWSColumn(ctx, idx, false)
 			wsCol = &offset
 		}

go/vt/vtgate/planbuilder/operators/ordering.go

@@ -86,7 +86,7 @@ func (o *Ordering) planOffsets(ctx *plancontext.PlanningContext) Operator {
 		offset := o.Source.AddColumn(ctx, true, false, aeWrap(order.SimplifiedExpr))
 		o.Offset = append(o.Offset, offset)
 
-		if !ctx.SemTable.NeedsWeightString(order.SimplifiedExpr) {
+		if !ctx.NeedsWeightString(order.SimplifiedExpr) {
 			o.WOffset = append(o.WOffset, -1)
 			continue
 		}

go/vt/vtgate/planbuilder/operators/queryprojection.go

@@ -88,7 +88,7 @@ type (
 )
 
 func (aggr Aggr) NeedsWeightString(ctx *plancontext.PlanningContext) bool {
-	return aggr.OpCode.NeedsComparableValues() && ctx.SemTable.NeedsWeightString(aggr.Func.GetArg())
+	return aggr.OpCode.NeedsComparableValues() && ctx.NeedsWeightString(aggr.Func.GetArg())
 }
 
 func (aggr Aggr) GetTypeCollation(ctx *plancontext.PlanningContext) evalengine.Type {

go/vt/vtgate/planbuilder/operators/route.go

@@ -805,7 +805,7 @@ func (r *Route) planOffsets(ctx *plancontext.PlanningContext) Operator {
 			WOffset:   -1,
 			Direction: order.Inner.Direction,
 		}
-		if ctx.SemTable.NeedsWeightString(order.SimplifiedExpr) {
+		if ctx.NeedsWeightString(order.SimplifiedExpr) {
 			ws := weightStringFor(order.SimplifiedExpr)
 			offset := r.AddColumn(ctx, true, false, aeWrap(ws))
 			o.WOffset = offset

go/vt/vtgate/planbuilder/plancontext/planning_context.go

@@ -21,6 +21,7 @@ import (
 	querypb "vitess.io/vitess/go/vt/proto/query"
 	"vitess.io/vitess/go/vt/sqlparser"
 	"vitess.io/vitess/go/vt/vterrors"
+	"vitess.io/vitess/go/vt/vtgate/engine/opcode"
 	"vitess.io/vitess/go/vt/vtgate/evalengine"
 	"vitess.io/vitess/go/vt/vtgate/semantics"
 )
@@ -212,7 +213,12 @@ func (ctx *PlanningContext) RewriteDerivedTableExpression(expr sqlparser.Expr, t
 func (ctx *PlanningContext) TypeForExpr(e sqlparser.Expr) (evalengine.Type, bool) {
 	t, found := ctx.SemTable.TypeForExpr(e)
 	if !found {
-		return t, found
+		typ := ctx.calculateTypeFor(e)
+		if typ.Valid() {
+			ctx.SemTable.ExprTypes[e] = typ
+			return typ, true
+		}
+		return evalengine.NewUnknownType(), false
 	}
 	deps := ctx.SemTable.RecursiveDeps(e)
 	// If the expression is from an outer table, it should be nullable
@@ -224,6 +230,89 @@ func (ctx *PlanningContext) TypeForExpr(e sqlparser.Expr) (evalengine.Type, bool
 	return t, true
 }
 
+func (ctx *PlanningContext) calculateTypeFor(e sqlparser.Expr) evalengine.Type {
+	cfg := &evalengine.Config{
+		ResolveType: func(expr sqlparser.Expr) (evalengine.Type, bool) {
+			col, isCol := expr.(*sqlparser.ColName)
+			if !isCol {
+				return evalengine.NewUnknownType(), false
+			}
+			return ctx.SemTable.TypeForExpr(col)
+		},
+		Collation:   ctx.SemTable.Collation,
+		Environment: ctx.VSchema.Environment(),
+		ResolveColumn: func(name *sqlparser.ColName) (int, error) {
+			// We don't need to resolve the column for type calculation
+			return 0, nil
+		},
+	}
+	env := evalengine.EmptyExpressionEnv(ctx.VSchema.Environment())
+
+	// We need to rewrite the aggregate functions to their corresponding types
+	// The evaluation engine compiler doesn't handle them, so we replace them with Arguments before
+	// asking the compiler for the type
+
+	// TODO: put this back in when we can calculate the aggregation types correctly
+	// expr, unknown := ctx.replaceAggrWithArg(e, cfg, env)
+	// if unknown {
+	// 	return evalengine.NewUnknownType()
+	// }
+
+	translatedExpr, err := evalengine.Translate(e, cfg)
+	if err != nil {
+		return evalengine.NewUnknownType()
+	}
+
+	typ, err := env.TypeOf(translatedExpr)
+	if err != nil {
+		return evalengine.NewUnknownType()
+	}
+	return typ
+}
+
+// replaceAggrWithArg replaces aggregate functions with Arguments in the given expression.
+// this is to prepare for sending the expression to the evalengine compiler to figure out the type
+func (ctx *PlanningContext) replaceAggrWithArg(e sqlparser.Expr, cfg *evalengine.Config, env *evalengine.ExpressionEnv) (expr sqlparser.Expr, unknown bool) {
+	expr = sqlparser.CopyOnRewrite(e, nil, func(cursor *sqlparser.CopyOnWriteCursor) {
+		agg, ok := cursor.Node().(sqlparser.AggrFunc)
+		if !ok {
+			return
+		}
+		code, ok := opcode.SupportedAggregates[agg.AggrName()]
+		if !ok {
+			// We don't know the type of this aggregate function
+			// The type calculation will be set to unknown
+			unknown = true
+			cursor.StopTreeWalk()
+			return
+		}
+		var inputType evalengine.Type
+		if arg := agg.GetArg(); arg != nil {
+			translatedExpr, err := evalengine.Translate(arg, cfg)
+			if err != nil {
+				unknown = true
+				cursor.StopTreeWalk()
+				return
+			}
+
+			inputType, err = env.TypeOf(translatedExpr)
+			if err != nil {
+				unknown = true
+				cursor.StopTreeWalk()
+				return
+			}
+		}
+		typ := code.ResolveType(inputType, ctx.VSchema.Environment().CollationEnv())
+		cursor.Replace(&sqlparser.Argument{
+			Name:  "arg",
+			Type:  typ.Type(),
+			Size:  typ.Size(),
+			Scale: typ.Scale(),
+		})
+	}, nil).(sqlparser.Expr)
+	return expr, unknown
+}
+
 // SQLTypeForExpr returns the sql type of the given expression, with nullable set if the expression is from an outer table.
 func (ctx *PlanningContext) SQLTypeForExpr(e sqlparser.Expr) sqltypes.Type {
 	t, found := ctx.TypeForExpr(e)
@@ -232,3 +321,21 @@ func (ctx *PlanningContext) SQLTypeForExpr(e sqlparser.Expr) sqltypes.Type {
 	}
 	return t.Type()
 }
+
+func (ctx *PlanningContext) NeedsWeightString(e sqlparser.Expr) bool {
+	switch e := e.(type) {
+	case *sqlparser.WeightStringFuncExpr, *sqlparser.Literal:
+		return false
+	default:
+		typ, found := ctx.TypeForExpr(e)
+		if !found {
+			return true
+		}
+
+		if !sqltypes.IsText(typ.Type()) {
+			return false
+		}
+
+		return !ctx.VSchema.Environment().CollationEnv().IsSupported(typ.Collation())
+	}
+}