6 files changed, 361 insertions, 3 deletions
diff --git a/internal/sqlutil/partition_offset_table.go b/internal/sqlutil/partition_offset_table.go
new file mode 100644
index 00000000..34882902
--- /dev/null
+++ b/internal/sqlutil/partition_offset_table.go
@@ -0,0 +1,126 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sqlutil
+
+import (
+	"context"
+	"database/sql"
+	"strings"
+
+	"github.com/matrix-org/util"
+)
+
+// A PartitionOffset is the offset into a partition of the input log.
+type PartitionOffset struct {
+	// The ID of the partition.
+	Partition int32
+	// The offset into the partition.
+	Offset int64
+}
+
+const partitionOffsetsSchema = `
+-- The offsets that the server has processed up to.
+CREATE TABLE IF NOT EXISTS ${prefix}_partition_offsets (
+    -- The name of the topic.
+    topic TEXT NOT NULL,
+    -- The 32-bit partition ID
+    partition INTEGER NOT NULL,
+    -- The 64-bit offset.
+    partition_offset BIGINT NOT NULL,
+    UNIQUE (topic, partition)
+);
+`
+
+const selectPartitionOffsetsSQL = "" +
+	"SELECT partition, partition_offset FROM ${prefix}_partition_offsets WHERE topic = $1"
+
+const upsertPartitionOffsetsSQL = "" +
+	"INSERT INTO ${prefix}_partition_offsets (topic, partition, partition_offset) VALUES ($1, $2, $3)" +
+	" ON CONFLICT (topic, partition)" +
+	" DO UPDATE SET partition_offset = $3"
+
+// PartitionOffsetStatements represents a set of statements that can be run on a partition_offsets table.
+type PartitionOffsetStatements struct {
+	selectPartitionOffsetsStmt *sql.Stmt
+	upsertPartitionOffsetStmt  *sql.Stmt
+}
+
+// Prepare converts the raw SQL statements into prepared statements.
+// Takes a prefix to prepend to the table name used to store the partition offsets.
+// This allows multiple components to share the same database schema.
+func (s *PartitionOffsetStatements) Prepare(db *sql.DB, prefix string) (err error) {
+	_, err = db.Exec(strings.Replace(partitionOffsetsSchema, "${prefix}", prefix, -1))
+	if err != nil {
+		return
+	}
+	if s.selectPartitionOffsetsStmt, err = db.Prepare(
+		strings.Replace(selectPartitionOffsetsSQL, "${prefix}", prefix, -1),
+	); err != nil {
+		return
+	}
+	if s.upsertPartitionOffsetStmt, err = db.Prepare(
+		strings.Replace(upsertPartitionOffsetsSQL, "${prefix}", prefix, -1),
+	); err != nil {
+		return
+	}
+	return
+}
+
+// PartitionOffsets implements PartitionStorer
+func (s *PartitionOffsetStatements) PartitionOffsets(
+	ctx context.Context, topic string,
+) ([]PartitionOffset, error) {
+	return s.selectPartitionOffsets(ctx, topic)
+}
+
+// SetPartitionOffset implements PartitionStorer
+func (s *PartitionOffsetStatements) SetPartitionOffset(
+	ctx context.Context, topic string, partition int32, offset int64,
+) error {
+	return s.upsertPartitionOffset(ctx, topic, partition, offset)
+}
+
+// selectPartitionOffsets returns all the partition offsets for the given topic.
+func (s *PartitionOffsetStatements) selectPartitionOffsets(
+	ctx context.Context, topic string,
+) ([]PartitionOffset, error) {
+	rows, err := s.selectPartitionOffsetsStmt.QueryContext(ctx, topic)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		err2 := rows.Close()
+		if err2 != nil {
+			util.GetLogger(ctx).WithError(err2).Error("selectPartitionOffsets: rows.close() failed")
+		}
+	}()
+	var results []PartitionOffset
+	for rows.Next() {
+		var offset PartitionOffset
+		if err := rows.Scan(&offset.Partition, &offset.Offset); err != nil {
+			return nil, err
+		}
+		results = append(results, offset)
+	}
+	return results, rows.Err()
+}
+
+// UpsertPartitionOffset updates or inserts the partition offset for the given topic.
+func (s *PartitionOffsetStatements) upsertPartitionOffset(
+	ctx context.Context, topic string, partition int32, offset int64,
+) error {
+	_, err := s.upsertPartitionOffsetStmt.ExecContext(ctx, topic, partition, offset)
+	return err
+}
diff --git a/internal/sqlutil/postgres.go b/internal/sqlutil/postgres.go
new file mode 100644
index 00000000..41a5508a
--- /dev/null
+++ b/internal/sqlutil/postgres.go
@@ -0,0 +1,25 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !wasm
+
+package sqlutil
+
+import "github.com/lib/pq"
+
+// IsUniqueConstraintViolationErr returns true if the error is a postgresql unique_violation error
+func IsUniqueConstraintViolationErr(err error) bool {
+	pqErr, ok := err.(*pq.Error)
+	return ok && pqErr.Code == "23505"
+}
diff --git a/internal/sqlutil/postgres_wasm.go b/internal/sqlutil/postgres_wasm.go
new file mode 100644
index 00000000..c45842f0
--- /dev/null
+++ b/internal/sqlutil/postgres_wasm.go
@@ -0,0 +1,22 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build wasm
+
+package sqlutil
+
+// IsUniqueConstraintViolationErr no-ops for this architecture
+func IsUniqueConstraintViolationErr(err error) bool {
+	return false
+}
diff --git a/internal/sqlutil/sql.go b/internal/sqlutil/sql.go
new file mode 100644
index 00000000..a25a4a5b
--- /dev/null
+++ b/internal/sqlutil/sql.go
@@ -0,0 +1,172 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sqlutil
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	"runtime"
+	"time"
+
+	"go.uber.org/atomic"
+)
+
+// ErrUserExists is returned if a username already exists in the database.
+var ErrUserExists = errors.New("Username already exists")
+
+// A Transaction is something that can be committed or rolledback.
+type Transaction interface {
+	// Commit the transaction
+	Commit() error
+	// Rollback the transaction.
+	Rollback() error
+}
+
+// EndTransaction ends a transaction.
+// If the transaction succeeded then it is committed, otherwise it is rolledback.
+// You MUST check the error returned from this function to be sure that the transaction
+// was applied correctly. For example, 'database is locked' errors in sqlite will happen here.
+func EndTransaction(txn Transaction, succeeded *bool) error {
+	if *succeeded {
+		return txn.Commit() // nolint: errcheck
+	} else {
+		return txn.Rollback() // nolint: errcheck
+	}
+}
+
+// WithTransaction runs a block of code passing in an SQL transaction
+// If the code returns an error or panics then the transactions is rolledback
+// Otherwise the transaction is committed.
+func WithTransaction(db *sql.DB, fn func(txn *sql.Tx) error) (err error) {
+	txn, err := db.Begin()
+	if err != nil {
+		return
+	}
+	succeeded := false
+	defer func() {
+		err2 := EndTransaction(txn, &succeeded)
+		if err == nil && err2 != nil { // failed to commit/rollback
+			err = err2
+		}
+	}()
+
+	err = fn(txn)
+	if err != nil {
+		return
+	}
+
+	succeeded = true
+	return
+}
+
+// TxStmt wraps an SQL stmt inside an optional transaction.
+// If the transaction is nil then it returns the original statement that will
+// run outside of a transaction.
+// Otherwise returns a copy of the statement that will run inside the transaction.
+func TxStmt(transaction *sql.Tx, statement *sql.Stmt) *sql.Stmt {
+	if transaction != nil {
+		statement = transaction.Stmt(statement)
+	}
+	return statement
+}
+
+// Hack of the century
+func QueryVariadic(count int) string {
+	return QueryVariadicOffset(count, 0)
+}
+
+func QueryVariadicOffset(count, offset int) string {
+	str := "("
+	for i := 0; i < count; i++ {
+		str += fmt.Sprintf("$%d", i+offset+1)
+		if i < (count - 1) {
+			str += ", "
+		}
+	}
+	str += ")"
+	return str
+}
+
+func SQLiteDriverName() string {
+	if runtime.GOOS == "js" {
+		return "sqlite3_js"
+	}
+	return "sqlite3"
+}
+
+// DbProperties functions return properties used by database/sql/DB
+type DbProperties interface {
+	MaxIdleConns() int
+	MaxOpenConns() int
+	ConnMaxLifetime() time.Duration
+}
+
+// TransactionWriter allows queuing database writes so that you don't
+// contend on database locks in, e.g. SQLite. Only one task will run
+// at a time on a given TransactionWriter.
+type TransactionWriter struct {
+	running atomic.Bool
+	todo    chan transactionWriterTask
+}
+
+func NewTransactionWriter() *TransactionWriter {
+	return &TransactionWriter{
+		todo: make(chan transactionWriterTask),
+	}
+}
+
+// transactionWriterTask represents a specific task.
+type transactionWriterTask struct {
+	db   *sql.DB
+	f    func(txn *sql.Tx) error
+	wait chan error
+}
+
+// Do queues a task to be run by a TransactionWriter. The function
+// provided will be ran within a transaction as supplied by the
+// database parameter. This will block until the task is finished.
+func (w *TransactionWriter) Do(db *sql.DB, f func(txn *sql.Tx) error) error {
+	if w.todo == nil {
+		return errors.New("not initialised")
+	}
+	if !w.running.Load() {
+		go w.run()
+	}
+	task := transactionWriterTask{
+		db:   db,
+		f:    f,
+		wait: make(chan error, 1),
+	}
+	w.todo <- task
+	return <-task.wait
+}
+
+// run processes the tasks for a given transaction writer. Only one
+// of these goroutines will run at a time. A transaction will be
+// opened using the database object from the task and then this will
+// be passed as a parameter to the task function.
+func (w *TransactionWriter) run() {
+	if !w.running.CAS(false, true) {
+		return
+	}
+	defer w.running.Store(false)
+	for task := range w.todo {
+		task.wait <- WithTransaction(task.db, func(txn *sql.Tx) error {
+			return task.f(txn)
+		})
+		close(task.wait)
+	}
+}
diff --git a/internal/sqlutil/trace.go b/internal/sqlutil/trace.go
index 1b008e1b..f6644d59 100644
--- a/internal/sqlutil/trace.go
+++ b/internal/sqlutil/trace.go
@@ -25,7 +25,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/matrix-org/dendrite/internal"
 	"github.com/ngrok/sqlmw"
 	"github.com/sirupsen/logrus"
 )
@@ -78,7 +77,7 @@ func (in *traceInterceptor) RowsNext(c context.Context, rows driver.Rows, dest [
 // Open opens a database specified by its database driver name and a driver-specific data source name,
 // usually consisting of at least a database name and connection information. Includes tracing driver
 // if DENDRITE_TRACE_SQL=1
-func Open(driverName, dsn string, dbProperties internal.DbProperties) (*sql.DB, error) {
+func Open(driverName, dsn string, dbProperties DbProperties) (*sql.DB, error) {
 	if tracingEnabled {
 		// install the wrapped driver
 		driverName += "-trace"
@@ -87,7 +86,7 @@ func Open(driverName, dsn string, dbProperties internal.DbProperties) (*sql.DB,
 	if err != nil {
 		return nil, err
 	}
-	if driverName != internal.SQLiteDriverName() && dbProperties != nil {
+	if driverName != SQLiteDriverName() && dbProperties != nil {
 		logrus.WithFields(logrus.Fields{
 			"MaxOpenConns":    dbProperties.MaxOpenConns(),
 			"MaxIdleConns":    dbProperties.MaxIdleConns(),
diff --git a/internal/sqlutil/uri.go b/internal/sqlutil/uri.go
index f72e0242..703258e6 100644
--- a/internal/sqlutil/uri.go
+++ b/internal/sqlutil/uri.go
@@ -1,3 +1,17 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package sqlutil
 
 import (