only store scalar expression instead of entire column

Author: angelamayxie

sql/planbuilder/aggregates.go

@@ -950,7 +950,7 @@ func (b *Builder) buildHaving(fromScope, projScope, outScope *scope, having *ast
 	havingScope := b.newScope()
 	if fromScope.parent != nil {
 		havingScope.parent = fromScope.parent
-		havingScope.parent.selectColumnAliases = fromScope.selectColumnAliases
+		havingScope.parent.selectAliases = fromScope.selectAliases
 	}
 
 	// add columns from fromScope referenced in the groupBy

sql/planbuilder/project.go

@@ -160,10 +160,10 @@ func (b *Builder) analyzeSelectList(inScope, outScope *scope, selectExprs ast.Se
 				col.scalar = e
 				tempScope.addColumn(col)
 			}
-			if inScope.selectColumnAliases == nil {
-				inScope.selectColumnAliases = make(map[string]scopeColumn)
+			if inScope.selectAliases == nil {
+				inScope.selectAliases = make(map[string]sql.Expression)
 			}
-			inScope.selectColumnAliases[e.Name()] = col
+			inScope.selectAliases[e.Name()] = e
 			exprs = append(exprs, e)
 		default:
 			exprs = append(exprs, pe)

sql/planbuilder/scalar.go

@@ -123,8 +123,8 @@ func (b *Builder) buildScalar(inScope *scope, e ast.Expr) (ex sql.Expression) {
 		colName := strings.ToLower(v.Name.String())
 		c, ok := inScope.resolveColumn(dbName, tblName, colName, true, false)
 		if !ok {
-			if alias, ok := inScope.selectColumnAliases[colName]; ok {
-				return alias.scalar
+			if aliasedExpr, ok := inScope.selectAliases[colName]; ok {
+				return aliasedExpr
 			}
 			sysVar, scope, ok := b.buildSysVar(v, ast.SetScope_None)
 			if ok {

sql/planbuilder/scope.go

@@ -62,7 +62,7 @@ type scope struct {
 	insertTableAlias    string
 	insertColumnAliases map[string]string
 
-	selectColumnAliases map[string]scopeColumn
+	selectAliases map[string]sql.Expression
 }
 
 // resolveColumn matches a variable use to a column definition with a unique
@@ -443,10 +443,10 @@ func (s *scope) copy() *scope {
 	if !s.colset.Empty() {
 		ret.colset = s.colset.Copy()
 	}
-	if s.selectColumnAliases != nil {
-		ret.selectColumnAliases = make(map[string]scopeColumn, len(s.selectColumnAliases))
-		for k, v := range s.selectColumnAliases {
-			ret.selectColumnAliases[k] = v
+	if s.selectAliases != nil {
+		ret.selectAliases = make(map[string]sql.Expression, len(s.selectAliases))
+		for k, v := range s.selectAliases {
+			ret.selectAliases[k] = v
 		}
 	}