private void maybeBeginImplicitTransaction()

in src/main/java/com/google/cloud/spanner/pgadapter/statements/BackendConnection.java [1228:1281]
42 lines of code
20 McCabe index (conditional complexity)

  private void maybeBeginImplicitTransaction(int index, boolean isSync) {
    if (connectionState != ConnectionState.IDLE) {
      return;
    }

    // Only start an implicit transaction if we have more than one statement left. Otherwise, just
    // let the Spanner connection execute the statement in auto-commit mode.
    if (isSync && index == bufferedStatements.size() - 1) {
      return;
    }
    // Don't start an implicit transaction if this is already a transaction statement.
    if (isTransactionStatement(index)) {
      return;
    }
    // No need to start a transaction for DDL or client side statements.
    if (bufferedStatements.get(index).parsedStatement.getType() == StatementType.DDL
        || bufferedStatements.get(index).parsedStatement.getType() == StatementType.CLIENT_SIDE) {
      return;
    }
    // If there are only DML statements left, those can be executed as an auto-commit dml batch.
    if (isSync && hasOnlyDmlStatementsAfter(index)) {
      return;
    }
    // Do not start a transaction if a batch is already active.
    if (spannerConnection.isDdlBatchActive() || spannerConnection.isDmlBatchActive()) {
      return;
    }
    // Do not start an implicit transaction if all that is in the buffer is a DESCRIBE and an
    // EXECUTE message for the same statement.
    if (isSync
        && bufferedStatements.size() == 2
        && bufferedStatements.get(0) instanceof Execute
        && bufferedStatements.get(1) instanceof Execute
        && ((Execute) bufferedStatements.get(0)).analyze
        && !((Execute) bufferedStatements.get(1)).analyze
        && bufferedStatements
            .get(0)
            .statement
            .getSql()
            .equals(bufferedStatements.get(1).statement.getSql())) {
      return;
    }

    // We need to start an implicit transaction.
    // Check if a read-only transaction suffices.
    spannerConnection.beginTransaction();
    if (isSync && !hasUpdateStatementsAfter(index)) {
      spannerConnection.setTransactionMode(
          com.google.cloud.spanner.connection.TransactionMode.READ_ONLY_TRANSACTION);
    }
    transactionMode = TransactionMode.IMPLICIT;
    connectionState = ConnectionState.TRANSACTION;
    currentTransactionId = UUID.randomUUID();
  }