Add support for SELECT_JSON statements.

mysql/select_json.go

@@ -0,0 +1,79 @@
+package mysql
+
+import (
+	"github.com/go-jet/jet/v2/internal/jet"
+)
+
+// SelectJsonStatement is an interface for MySQL statements that generate JSON on the server.
+type SelectJsonStatement interface {
+	Statement
+	jet.Serializer
+
+	AS(alias string) Projection
+
+	FROM(table ReadableTable) SelectJsonStatement
+	WHERE(condition BoolExpression) SelectJsonStatement
+	ORDER_BY(orderByClauses ...OrderByClause) SelectJsonStatement
+	LIMIT(limit int64) SelectJsonStatement
+	OFFSET(offset int64) SelectJsonStatement
+}
+
+// SELECT_JSON_ARR creates a new SelectJsonStatement with a list of projections.
+func SELECT_JSON_ARR(projections ...Projection) SelectJsonStatement {
+	return newSelectStatementJson(projections, jet.SelectJsonArrStatementType)
+}
+
+// SELECT_JSON_OBJ creates a new SelectJsonStatement with a list of projections.
+func SELECT_JSON_OBJ(projections ...Projection) SelectJsonStatement {
+	return newSelectStatementJson(projections, jet.SelectJsonObjStatementType)
+}
+
+type selectJsonStatement struct {
+	*selectStatementImpl
+}
+
+func newSelectStatementJson(projections []Projection, statementType jet.StatementType) SelectJsonStatement {
+	newSelect := &selectJsonStatement{
+		selectStatementImpl: newSelectStatement(statementType, nil, nil),
+	}
+
+	newSelect.Select.ProjectionList = ProjectionList{constructJsonFunc(projections, statementType).AS("json")}
+
+	return newSelect
+}
+
+func constructJsonFunc(projections []Projection, statementType jet.StatementType) Expression {
+	jsonObj := Func("JSON_OBJECT", CustomExpression(jet.JsonProjectionList(projections)))
+
+	if statementType == jet.SelectJsonArrStatementType {
+		return Func("JSON_ARRAYAGG", jsonObj)
+	}
+
+	return jsonObj
+}
+
+func (s *selectJsonStatement) FROM(table ReadableTable) SelectJsonStatement {
+	s.From.Tables = []jet.Serializer{table}
+
+	return s
+}
+
+func (s *selectJsonStatement) WHERE(condition BoolExpression) SelectJsonStatement {
+	s.Where.Condition = condition
+	return s
+}
+
+func (s *selectJsonStatement) ORDER_BY(orderByClauses ...OrderByClause) SelectJsonStatement {
+	s.OrderBy.List = orderByClauses
+	return s
+}
+
+func (s *selectJsonStatement) LIMIT(limit int64) SelectJsonStatement {
+	s.Limit.Count = limit
+	return s
+}
+
+func (s *selectJsonStatement) OFFSET(offset int64) SelectJsonStatement {
+	s.Offset.Count = Int(offset)
+	return s
+}