Encode json values implicitly in the sql queries according the golang json package spec.

internal/jet/alias.go

@@ -18,10 +18,45 @@ func (a *alias) fromImpl(subQuery SelectTable) Projection {
 	// Generated columns have default aliasing.
 	tableName, columnName := extractTableAndColumnName(a.alias)
 
-	column := NewColumnImpl(columnName, tableName, nil)
-	column.subQuery = subQuery
+	newDummyColumn := newDummyColumnForExpression(a.expression, columnName)
+	newDummyColumn.setTableName(tableName)
+	newDummyColumn.setSubQuery(subQuery)
 
-	return &column
+	return newDummyColumn
+}
+
+// This function is used to create dummy columns when exporting sub-query columns using subQuery.AllColumns()
+// In most case we don't care about type of the column, except when sub-query columns are used as SELECT_JSON projection.
+// We need to know type to encode value for json unmarshal. At the moment only bool, time and blob columns are of interest,
+// so we don't have to support every column type.
+func newDummyColumnForExpression(exp Expression, name string) ColumnExpression {
+
+	switch exp.(type) {
+	case BoolExpression:
+		return BoolColumn(name)
+	case IntegerExpression:
+		return IntegerColumn(name)
+	case FloatExpression:
+		return FloatColumn(name)
+	case BlobExpression:
+		return BlobColumn(name)
+	case DateExpression:
+		return DateColumn(name)
+	case TimeExpression:
+		return TimeColumn(name)
+	case TimezExpression:
+		return TimezColumn(name)
+	case TimestampExpression:
+		return TimestampColumn(name)
+	case TimestampzExpression:
+		return TimestampzColumn(name)
+	case IntervalExpression:
+		return IntervalColumn(name)
+	case StringExpression:
+		return StringColumn(name)
+	}
+
+	return StringColumn(name)
 }
 
 func (a *alias) serializeForProjection(statement StatementType, out *SQLBuilder) {
@@ -31,7 +66,14 @@ func (a *alias) serializeForProjection(statement StatementType, out *SQLBuilder)
 	out.WriteAlias(a.alias)
 }
 
-func (a *alias) serializeForJsonObj(statement StatementType, out *SQLBuilder) {
+func (a *alias) serializeForJsonObjEntry(statement StatementType, out *SQLBuilder) {
 	out.WriteJsonObjKey(a.alias)
-	a.expression.serialize(statement, out)
+	a.expression.serializeForJsonValue(statement, out)
+}
+
+func (a *alias) serializeForRowToJsonProjection(statement StatementType, out *SQLBuilder) {
+	a.expression.serializeForJsonValue(statement, out)
+
+	out.WriteString("AS")
+	out.WriteAlias(a.alias)
 }