feat: coerce the selected value before setting it on the child

Signed-off-by: Manan Gupta <[email protected]>

go/vt/vtgate/engine/fk_cascade.go

@@ -25,6 +25,7 @@ import (
 	querypb "vitess.io/vitess/go/vt/proto/query"
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
 	"vitess.io/vitess/go/vt/vterrors"
+	"vitess.io/vitess/go/vt/vtgate/evalengine"
 )
 
 // FkChild contains the Child Primitive to be executed collecting the values from the Selection Primitive using the column indexes.
@@ -40,14 +41,16 @@ type FkChild struct {
 }
 
 // NonLiteralUpdateInfo stores the information required to process non-literal update queries.
-// It stores 3 information-
-// 1. UpdateExprCol- The index of the updated expression in the select query.
-// 2. UpdateExprBvName- The bind variable name to store the updated expression into.
-// 3. CompExprCol- The index of the comparison expression in the select query to know if the row value is actually being changed or not.
+// It stores 4 information-
+// 1. ExprCol- The index of the column being updated in the select query.
+// 2. CompExprCol- The index of the comparison expression in the select query to know if the row value is actually being changed or not.
+// 3. UpdateExprCol- The index of the updated expression in the select query.
+// 4. UpdateExprBvName- The bind variable name to store the updated expression into.
 type NonLiteralUpdateInfo struct {
+	ExprCol          int
+	CompExprCol      int
 	UpdateExprCol    int
 	UpdateExprBvName string
-	CompExprCol      int
 }
 
 // FkCascade is a primitive that implements foreign key cascading using Selection as values required to execute the FkChild Primitives.
@@ -185,7 +188,15 @@ func (fkc *FkCascade) executeNonLiteralExprFkChild(ctx context.Context, vcursor
 
 		// Next, we need to copy the updated expressions value into the bind variables map.
 		for _, info := range child.NonLiteralInfo {
-			bindVars[info.UpdateExprBvName] = sqltypes.ValueBindVariable(row[info.UpdateExprCol])
+			// Type case the value to that of the column that we are updating.
+			// This is required for example when we receive an updated float value of -0, but
+			// the column being updated is a varchar column, then if we don't coerce the value of -0 to
+			// varchar, MySQL ends up setting it to '0' instead of '-0'.
+			finalVal, err := evalengine.CoerceTo(row[info.UpdateExprCol], selectionRes.Fields[info.ExprCol].Type)
+			if err != nil {
+				return err
+			}
+			bindVars[info.UpdateExprBvName] = sqltypes.ValueBindVariable(finalVal)
 		}
 		_, err := vcursor.ExecutePrimitive(ctx, child.Exec, bindVars, wantfields)
 		if err != nil {

go/vt/vtgate/planbuilder/operators/update.go

@@ -334,6 +334,7 @@ func addNonLiteralUpdExprToSelect(ctx *plancontext.PlanningContext, updExpr *sql
 	info := engine.NonLiteralUpdateInfo{
 		CompExprCol:   -1,
 		UpdateExprCol: -1,
+		ExprCol:       -1,
 	}
 	// Add the expressions to the select expressions. We make sure to reuse the offset if it has already been added once.
 	for idx, selectExpr := range exprs {
@@ -343,6 +344,9 @@ func addNonLiteralUpdExprToSelect(ctx *plancontext.PlanningContext, updExpr *sql
 		if ctx.SemTable.EqualsExpr(selectExpr.(*sqlparser.AliasedExpr).Expr, updExpr.Expr) {
 			info.UpdateExprCol = idx
 		}
+		if ctx.SemTable.EqualsExpr(selectExpr.(*sqlparser.AliasedExpr).Expr, updExpr.Name) {
+			info.ExprCol = idx
+		}
 	}
 	// If the expression doesn't exist, then we add the expression and store the offset.
 	if info.CompExprCol == -1 {
@@ -353,6 +357,10 @@ func addNonLiteralUpdExprToSelect(ctx *plancontext.PlanningContext, updExpr *sql
 		info.UpdateExprCol = len(exprs)
 		exprs = append(exprs, aeWrap(updExpr.Expr))
 	}
+	if info.ExprCol == -1 {
+		info.ExprCol = len(exprs)
+		exprs = append(exprs, aeWrap(updExpr.Name))
+	}
 	return info, exprs
 }