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// 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"
)
// 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 = $3"
// PartitionOffsetStatements represents a set of statements that can be run on a partition_offsets table.
type PartitionOffsetStatements struct {
db *sql.DB
writer Writer
selectPartitionOffsetsStmt *sql.Stmt
upsertPartitionOffsetStmt *sql.Stmt
}
// Prepare converts the raw SQL statements into prepared statements.
// Takes a prefix to prepend to the table name used to store the partition offsets.
// This allows multiple components to share the same database schema.
func (s *PartitionOffsetStatements) Prepare(db *sql.DB, writer Writer, prefix string) (err error) {
s.db = db
s.writer = writer
_, err = db.Exec(strings.Replace(partitionOffsetsSchema, "${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,
) (results []PartitionOffset, err error) {
rows, err := s.selectPartitionOffsetsStmt.QueryContext(ctx, topic)
if err != nil {
return nil, err
}
defer checkNamedErr(rows.Close, &err)
for rows.Next() {
var offset PartitionOffset
if err = rows.Scan(&offset.Partition, &offset.Offset); err != nil {
return nil, err
}
results = append(results, offset)
}
err = rows.Err()
return results, err
}
// checkNamedErr calls fn and overwrite err if it was nil and fn returned non-nil
func checkNamedErr(fn func() error, err *error) {
if e := fn(); e != nil && *err == nil {
*err = e
}
}
// 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 {
return s.writer.Do(s.db, nil, func(txn *sql.Tx) error {
stmt := TxStmt(txn, s.upsertPartitionOffsetStmt)
_, err := stmt.ExecContext(ctx, topic, partition, offset)
return err
})
}
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