init - add project files

tools/jet-2.12.0/internal/jet/projection.go

@@ -0,0 +1,81 @@
+package jet
+
+// Projection is interface for all projection types. Types that can be part of, for instance SELECT clause.
+type Projection interface {
+	serializeForProjection(statement StatementType, out *SQLBuilder)
+	fromImpl(subQuery SelectTable) Projection
+}
+
+// SerializeForProjection is helper function for serializing projection outside of jet package
+func SerializeForProjection(projection Projection, statementType StatementType, out *SQLBuilder) {
+	projection.serializeForProjection(statementType, out)
+}
+
+// ProjectionList is a redefined type, so that ProjectionList can be used as a Projection.
+type ProjectionList []Projection
+
+func (pl ProjectionList) fromImpl(subQuery SelectTable) Projection {
+	newProjectionList := ProjectionList{}
+
+	for _, projection := range pl {
+		newProjectionList = append(newProjectionList, projection.fromImpl(subQuery))
+	}
+
+	return newProjectionList
+}
+
+func (pl ProjectionList) serializeForProjection(statement StatementType, out *SQLBuilder) {
+	SerializeProjectionList(statement, pl, out)
+}
+
+// As will create new projection list where each column is wrapped with a new table alias.
+// tableAlias should be in the form 'name' or 'name.*', or it can be an empty string, which will remove existing table alias.
+// For instance: If projection list has a column 'Artist.Name', and tableAlias is 'Musician.*', returned projection list will
+// have a column wrapped in alias 'Musician.Name'. If tableAlias is empty string, it removes existing table alias ('Artist.Name' becomes 'Name').
+func (pl ProjectionList) As(tableAlias string) ProjectionList {
+	newProjectionList := ProjectionList{}
+
+	for _, projection := range pl {
+		switch p := projection.(type) {
+		case ProjectionList:
+			newProjectionList = append(newProjectionList, p.As(tableAlias))
+		case ColumnList:
+			newProjectionList = append(newProjectionList, p.As(tableAlias))
+		case ColumnExpression:
+			newProjectionList = append(newProjectionList, newAlias(p, joinAlias(tableAlias, p.Name())))
+		case *alias:
+			newAlias := *p
+			_, columnName := extractTableAndColumnName(newAlias.alias)
+			newAlias.alias = joinAlias(tableAlias, columnName)
+			newProjectionList = append(newProjectionList, &newAlias)
+		}
+	}
+
+	return newProjectionList
+}
+
+// Except will create new projection list in which columns contained in excluded column names are removed
+func (pl ProjectionList) Except(toExclude ...Column) ProjectionList {
+	excludedColumnList := UnwidColumnList(toExclude)
+	excludedColumnNames := map[string]bool{}
+
+	for _, excludedColumn := range excludedColumnList {
+		excludedColumnNames[excludedColumn.Name()] = true
+	}
+
+	var ret ProjectionList
+
+	for _, projection := range pl {
+		switch p := projection.(type) {
+		case ProjectionList:
+			ret = append(ret, p.Except(toExclude...))
+		case ColumnExpression:
+			if excludedColumnNames[p.Name()] {
+				continue
+			}
+			ret = append(ret, p)
+		}
+	}
+
+	return ret
+}