Merge pull request #922 from go-kivik/preparedStatements

Cache prepared statements

.golangci.toml

@@ -55,3 +55,8 @@ 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."""
+
+# Prepared statements on transactions are closed by the transaction.
+[[issues.exclude-rules]]
+source = "tx.Prepare|stmts.prepare"
+linters = ["sqlclosecheck"]

x/sqlite/util.go

@@ -90,6 +90,25 @@ func (d *db) winningRev(ctx context.Context, tx *sql.Tx, docID string) (revision
  return curRev, hash, err
 }
 
+type stmtCache map[string]*sql.Stmt
+
+func newStmtCache() stmtCache {
+ return make(stmtCache)
+}
+
+func (c stmtCache) prepare(ctx context.Context, tx *sql.Tx, query string) (*sql.Stmt, error) {
+ stmt, ok := c[query]
+ if !ok {
+ var err error
+ stmt, err = tx.PrepareContext(ctx, query)
+ if err != nil {
+ return nil, err
+ }
+ c[query] = stmt
+ }
+ return stmt, nil
+}
+
 // createRev creates a new entry in the revs table, inserts the document data
 // into the docs table, attachments into the attachments table, and returns the
 // new revision.
@@ -144,47 +163,28 @@ func (d *db) createRev(ctx context.Context, tx *sql.Tx, data *docData, curRev re
  }
  sort.Strings(orderedFilenames)
 
- attStmt, err := tx.PrepareContext(ctx, d.query(`
- INSERT INTO {{ .Attachments }} (rev_pos, filename, content_type, length, digest, data)
- VALUES ($1, $2, $3, $4, $5, $6)
- RETURNING pk
- `))
- if err != nil {
- return r, err
- }
- defer attStmt.Close()
-
- stubStmt, err := tx.PrepareContext(ctx, d.query(`
- INSERT INTO {{ .AttachmentsBridge }} (pk, id, rev, rev_id)
- SELECT att.pk, $1, $2, $3
- FROM {{ .Attachments }} AS att
- JOIN {{ .AttachmentsBridge }} AS bridge ON att.pk = bridge.pk
- WHERE bridge.id = $1
- AND bridge.rev = $4
- AND bridge.rev_id = $5
- AND att.filename = $6
- RETURNING pk
- `))
- if err != nil {
- return r, err
- }
- defer stubStmt.Close()
-
- bridgeStmt, err := tx.PrepareContext(ctx, d.query(`
- INSERT INTO {{ .AttachmentsBridge }} (pk, id, rev, rev_id)
- VALUES ($1, $2, $3, $4)
- `))
- if err != nil {
- return r, err
- }
- defer bridgeStmt.Close()
+ stmts := newStmtCache()
 
  for _, filename := range orderedFilenames {
  att := data.Attachments[filename]
 
  var pk int
  if att.Stub {
- err := stubStmt.QueryRowContext(ctx, data.ID, r.rev, r.id, curRev.rev, curRev.id, filename).Scan(&pk)
+ stubStmt, err := stmts.prepare(ctx, tx, d.query(`
+ INSERT INTO {{ .AttachmentsBridge }} (pk, id, rev, rev_id)
+ SELECT att.pk, $1, $2, $3
+ FROM {{ .Attachments }} AS att
+ JOIN {{ .AttachmentsBridge }} AS bridge ON att.pk = bridge.pk
+ WHERE bridge.id = $1
+ AND bridge.rev = $4
+ AND bridge.rev_id = $5
+ AND att.filename = $6
+ RETURNING pk
+ `))
+ if err != nil {
+ return r, err
+ }
+ err = stubStmt.QueryRowContext(ctx, data.ID, r.rev, r.id, curRev.rev, curRev.id, filename).Scan(&pk)
  switch {
  case errors.Is(err, sql.ErrNoRows):
  return r, &internal.Error{Status: http.StatusPreconditionFailed, Message: fmt.Sprintf("invalid attachment stub in bar for %s", filename)}
@@ -199,11 +199,28 @@ func (d *db) createRev(ctx context.Context, tx *sql.Tx, data *docData, curRev re
  if contentType == "" {
  contentType = "application/octet-stream"
  }
- err := attStmt.QueryRowContext(ctx, r.rev, filename, contentType, att.Length, att.Digest, att.Content).Scan(&pk)
+
+ attStmt, err := stmts.prepare(ctx, tx, d.query(`
+ INSERT INTO {{ .Attachments }} (rev_pos, filename, content_type, length, digest, data)
+ VALUES ($1, $2, $3, $4, $5, $6)
+ RETURNING pk
+ `))
+ if err != nil {
+ return r, err
+ }
+
+ err = attStmt.QueryRowContext(ctx, r.rev, filename, contentType, att.Length, att.Digest, att.Content).Scan(&pk)
  if err != nil {
  return r, err
  }
 
+ bridgeStmt, err := stmts.prepare(ctx, tx, d.query(`
+ INSERT INTO {{ .AttachmentsBridge }} (pk, id, rev, rev_id)
+ VALUES ($1, $2, $3, $4)
+ `))
+ if err != nil {
+ return r, err
+ }
  _, err = bridgeStmt.ExecContext(ctx, pk, data.ID, r.rev, r.id)
  if err != nil {
  return r, err