kvdb/postgres: remove global application level lock

kvdb/postgres/db.go

@@ -28,7 +28,6 @@ func newPostgresBackend(ctx context.Context, config *Config, prefix string) (
  Schema: "public",
  TableNamePrefix: prefix,
  SQLiteCmdReplacements: sqliteCmdReplacements,
- WithTxLevelLock: true,
  }
 
  return sqlbase.NewSqlBackend(ctx, cfg)

kvdb/sqlbase/db.go

@@ -55,10 +55,6 @@ type Config struct {
  // commands. Note that the sqlite keywords to be replaced are
  // case-sensitive.
  SQLiteCmdReplacements SQLiteCmdReplacements
-
- // WithTxLevelLock when set will ensure that there is a transaction
- // level lock.
- WithTxLevelLock bool
 }
 
 // db holds a reference to the sql db connection.
@@ -79,10 +75,6 @@ type db struct {
  // db is the underlying database connection instance.
  db *sql.DB
 
- // lock is the global write lock that ensures single writer. This is
- // only used if cfg.WithTxLevelLock is set.
- lock sync.RWMutex
-
  // table is the name of the table that contains the data for all
  // top-level buckets that have keys that cannot be mapped to a distinct
  // sql table.

kvdb/sqlbase/readwrite_tx.go

@@ -5,7 +5,6 @@ package sqlbase
 import (
  "context"
  "database/sql"
- "sync"
 
  "github.com/btcsuite/btcwallet/walletdb"
 )
@@ -20,28 +19,11 @@ type readWriteTx struct {
 
  // active is true if the transaction hasn't been committed yet.
  active bool
-
- // locker is a pointer to the global db lock.
- locker sync.Locker
 }
 
 // newReadWriteTx creates an rw transaction using a connection from the
 // specified pool.
 func newReadWriteTx(db *db, readOnly bool) (*readWriteTx, error) {
- locker := newNoopLocker()
- if db.cfg.WithTxLevelLock {
- // Obtain the global lock instance. An alternative here is to
- // obtain a database lock from Postgres. Unfortunately there is
- // no database-level lock in Postgres, meaning that each table
- // would need to be locked individually. Perhaps an advisory
- // lock could perform this function too.
- locker = &db.lock
- if readOnly {
- locker = db.lock.RLocker()
- }
- }
- locker.Lock()
-
  // Start the transaction. Don't use the timeout context because it would
  // be applied to the transaction as a whole. If possible, mark the
  // transaction as read-only to make sure that potential programming
@@ -54,15 +36,13 @@ func newReadWriteTx(db *db, readOnly bool) (*readWriteTx, error) {
  },
  )
  if err != nil {
- locker.Unlock()
  return nil, err
  }
 
  return &readWriteTx{
  db: db,
  tx: tx,
  active: true,
- locker: locker,
  }, nil
 }
 
@@ -94,7 +74,6 @@ func (tx *readWriteTx) Rollback() error {
 
  // Unlock the transaction regardless of the error result.
  tx.active = false
- tx.locker.Unlock()
  return err
 }
 
@@ -162,7 +141,6 @@ func (tx *readWriteTx) Commit() error {
 
  // Unlock the transaction regardless of the error result.
  tx.active = false
- tx.locker.Unlock()
 
  return err
 }
@@ -204,25 +182,3 @@ func (tx *readWriteTx) Exec(query string, args ...interface{}) (sql.Result,
 
  return tx.tx.ExecContext(ctx, query, args...)
 }
-
-// noopLocker is an implementation of a no-op sync.Locker.
-type noopLocker struct{}
-
-// newNoopLocker creates a new noopLocker.
-func newNoopLocker() sync.Locker {
- return &noopLocker{}
-}
-
-// Lock is a noop.
-//
-// NOTE: this is part of the sync.Locker interface.
-func (n *noopLocker) Lock() {
-}
-
-// Unlock is a noop.
-//
-// NOTE: this is part of the sync.Locker interface.
-func (n *noopLocker) Unlock() {
-}
-
-var _ sync.Locker = (*noopLocker)(nil)