dendrite/common/partition_offset_table.go
Kiril Vladimiroff d5dbe546e4
Always defer *sql.Rows.Close and consult with Err (#844)
* Always defer *sql.Rows.Close and consult with Err

database/sql.Rows.Next() makes sure to call Close only after exhausting
result rows which would NOT happen when returning early from a bad Scan.
Close being idempotent makes it a great candidate to get always deferred
regardless of what happens later on the result set.

This change also makes sure call Err() after exhausting Next() and
propagate non-nil results from it as the documentation advises.

Closes #764

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

* Override named result parameters in last returns

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

* Do the same over new changes that got merged

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>
2020-02-11 14:12:21 +00:00

112 lines
3.7 KiB
Go

// Copyright 2017 Vector Creations Ltd
//
// 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 common
import (
"context"
"database/sql"
"strings"
)
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,
CONSTRAINT ${prefix}_topic_partition_unique 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 ON CONSTRAINT ${prefix}_topic_partition_unique" +
" 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 rows.Close() // nolint: errcheck
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
}