Add helper method for preparing lists of statements. (#25)

* Add helper method for preparing lists of statements.

src/github.com/matrix-org/dendrite/roomserver/storage/event_json_table.go

@@ -44,13 +44,10 @@ func (s *eventJSONStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertEventJSONStmt, err = db.Prepare(insertEventJSONSQL); err != nil {
+	return statementList{
-		return
+		{&s.insertEventJSONStmt, insertEventJSONSQL},
-	}
+		{&s.bulkSelectEventJSONStmt, bulkSelectEventJSONSQL},
-	if s.bulkSelectEventJSONStmt, err = db.Prepare(bulkSelectEventJSONSQL); err != nil {
+	}.prepare(db)
-		return
-	}
-	return
 }
 
 func (s *eventJSONStatements) insertEventJSON(eventNID types.EventNID, eventJSON []byte) error {

src/github.com/matrix-org/dendrite/roomserver/storage/event_state_keys_table.go

@@ -53,16 +53,11 @@ func (s *eventStateKeyStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertEventStateKeyNIDStmt, err = db.Prepare(insertEventStateKeyNIDSQL); err != nil {
+	return statementList{
-		return
+		{&s.insertEventStateKeyNIDStmt, insertEventStateKeyNIDSQL},
-	}
+		{&s.selectEventStateKeyNIDStmt, selectEventStateKeyNIDSQL},
-	if s.selectEventStateKeyNIDStmt, err = db.Prepare(selectEventStateKeyNIDSQL); err != nil {
+		{&s.bulkSelectEventStateKeyNIDStmt, bulkSelectEventStateKeyNIDSQL},
-		return
+	}.prepare(db)
-	}
-	if s.bulkSelectEventStateKeyNIDStmt, err = db.Prepare(bulkSelectEventStateKeyNIDSQL); err != nil {
-		return
-	}
-	return
 }
 
 func (s *eventStateKeyStatements) insertEventStateKeyNID(eventStateKey string) (types.EventStateKeyNID, error) {

src/github.com/matrix-org/dendrite/roomserver/storage/event_types_table.go

@@ -76,13 +76,11 @@ func (s *eventTypeStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertEventTypeNIDStmt, err = db.Prepare(insertEventTypeNIDSQL); err != nil {
+
-		return
+	return statementList{
-	}
+		{&s.insertEventTypeNIDStmt, insertEventTypeNIDSQL},
-	if s.selectEventTypeNIDStmt, err = db.Prepare(selectEventTypeNIDSQL); err != nil {
+		{&s.selectEventTypeNIDStmt, selectEventTypeNIDSQL},
-		return
+	}.prepare(db)
-	}
-	return
 }
 
 func (s *eventTypeStatements) insertEventTypeNID(eventType string) (types.EventTypeNID, error) {

src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go

@@ -110,10 +110,7 @@ func (s *eventStatements) prepare(db *sql.DB) (err error) {
 		return
 	}
 
-	statements := []struct {
+	return statementList{
-		statement **sql.Stmt
-		sql       string
-	}{
 		{&s.insertEventStmt, insertEventSQL},
 		{&s.selectEventStmt, selectEventSQL},
 		{&s.bulkSelectStateEventByIDStmt, bulkSelectStateEventByIDSQL},
@@ -125,15 +122,7 @@ func (s *eventStatements) prepare(db *sql.DB) (err error) {
 		{&s.bulkSelectStateAtEventAndReferenceStmt, bulkSelectStateAtEventAndReferenceSQL},
 		{&s.bulkSelectEventReferenceStmt, bulkSelectEventReferenceSQL},
 		{&s.bulkSelectEventIDStmt, bulkSelectEventIDSQL},
-	}
+	}.prepare(db)
-
-	for _, statement := range statements {
-		if *statement.statement, err = db.Prepare(statement.sql); err != nil {
-			return
-		}
-	}
-
-	return
 }
 
 func (s *eventStatements) insertEvent(

src/github.com/matrix-org/dendrite/roomserver/storage/partition_offset_table.go

@@ -36,13 +36,11 @@ func (s *partitionOffsetStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.selectPartitionOffsetsStmt, err = db.Prepare(selectPartitionOffsetsSQL); err != nil {
+
-		return
+	return statementList{
-	}
+		{&s.selectPartitionOffsetsStmt, selectPartitionOffsetsSQL},
-	if s.upsertPartitionOffsetStmt, err = db.Prepare(upsertPartitionOffsetsSQL); err != nil {
+		{&s.upsertPartitionOffsetStmt, upsertPartitionOffsetsSQL},
-		return
+	}.prepare(db)
-	}
-	return
 }
 
 func (s *partitionOffsetStatements) selectPartitionOffsets(topic string) ([]types.PartitionOffset, error) {

src/github.com/matrix-org/dendrite/roomserver/storage/prepare.go

@@ -0,0 +1,21 @@
+package storage
+
+import (
+	"database/sql"
+)
+
+// a statementList is a list of SQL statements to prepare and a pointer to where to store the resulting prepared statement.
+type statementList []struct {
+	statement **sql.Stmt
+	sql       string
+}
+
+// prepare the SQL for each statement in the list and assign the result to the prepared statement.
+func (s statementList) prepare(db *sql.DB) (err error) {
+	for _, statement := range s {
+		if *statement.statement, err = db.Prepare(statement.sql); err != nil {
+			return
+		}
+	}
+	return
+}

src/github.com/matrix-org/dendrite/roomserver/storage/previous_events_table.go

@@ -50,13 +50,11 @@ func (s *previousEventStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertPreviousEventStmt, err = db.Prepare(insertPreviousEventSQL); err != nil {
+
-		return
+	return statementList{
-	}
+		{&s.insertPreviousEventStmt, insertPreviousEventSQL},
-	if s.selectPreviousEventExistsStmt, err = db.Prepare(selectPreviousEventExistsSQL); err != nil {
+		{&s.selectPreviousEventExistsStmt, selectPreviousEventExistsSQL},
-		return
+	}.prepare(db)
-	}
-	return
 }
 
 func (s *previousEventStatements) insertPreviousEvent(txn *sql.Tx, previousEventID string, previousEventReferenceSHA256 []byte, eventNID types.EventNID) error {

src/github.com/matrix-org/dendrite/roomserver/storage/rooms_table.go

@@ -56,22 +56,13 @@ func (s *roomStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertRoomNIDStmt, err = db.Prepare(insertRoomNIDSQL); err != nil {
+	return statementList{
-		return
+		{&s.insertRoomNIDStmt, insertRoomNIDSQL},
-	}
+		{&s.selectRoomNIDStmt, selectRoomNIDSQL},
-	if s.selectRoomNIDStmt, err = db.Prepare(selectRoomNIDSQL); err != nil {
+		{&s.selectLatestEventNIDsStmt, selectLatestEventNIDsSQL},
-		return
+		{&s.selectLatestEventNIDsForUpdateStmt, selectLatestEventNIDsForUpdateSQL},
-	}
+		{&s.updateLatestEventNIDsStmt, updateLatestEventNIDsSQL},
-	if s.selectLatestEventNIDsStmt, err = db.Prepare(selectLatestEventNIDsSQL); err != nil {
+	}.prepare(db)
-		return
-	}
-	if s.selectLatestEventNIDsForUpdateStmt, err = db.Prepare(selectLatestEventNIDsForUpdateSQL); err != nil {
-		return
-	}
-	if s.updateLatestEventNIDsStmt, err = db.Prepare(updateLatestEventNIDsSQL); err != nil {
-		return
-	}
-	return
 }
 
 func (s *roomStatements) insertRoomNID(roomID string) (types.RoomNID, error) {

src/github.com/matrix-org/dendrite/roomserver/storage/state_block_table.go

@@ -57,16 +57,12 @@ func (s *stateBlockStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertStateDataStmt, err = db.Prepare(insertStateDataSQL); err != nil {
+
-		return
+	return statementList{
-	}
+		{&s.insertStateDataStmt, insertStateDataSQL},
-	if s.selectNextStateBlockNIDStmt, err = db.Prepare(selectNextStateBlockNIDSQL); err != nil {
+		{&s.selectNextStateBlockNIDStmt, selectNextStateBlockNIDSQL},
-		return
+		{&s.bulkSelectStateDataEntriesStmt, bulkSelectStateDataEntriesSQL},
-	}
+	}.prepare(db)
-	if s.bulkSelectStateDataEntriesStmt, err = db.Prepare(bulkSelectStateDataEntriesSQL); err != nil {
-		return
-	}
-	return
 }
 
 func (s *stateBlockStatements) bulkInsertStateData(stateBlockNID types.StateBlockNID, entries []types.StateEntry) error {

src/github.com/matrix-org/dendrite/roomserver/storage/state_snapshot_table.go

@@ -52,13 +52,11 @@ func (s *stateSnapshotStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertStateStmt, err = db.Prepare(insertStateSQL); err != nil {
+
-		return
+	return statementList{
-	}
+		{&s.insertStateStmt, insertStateSQL},
-	if s.bulkSelectStateBlockNIDsStmt, err = db.Prepare(bulkSelectStateBlockNIDsSQL); err != nil {
+		{&s.bulkSelectStateBlockNIDsStmt, bulkSelectStateBlockNIDsSQL},
-		return
+	}.prepare(db)
-	}
-	return
 }
 
 func (s *stateSnapshotStatements) insertState(roomNID types.RoomNID, stateBlockNIDs []types.StateBlockNID) (stateNID types.StateSnapshotNID, err error) {