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Verwandte Themen

Database abstraction layer

Allow the use of different database servers using the same code base.

Code

includes/database/query.inc, line 678

<?php
public function execute() {

  // A merge query without any key field is invalid.
  if (count($this->keyFields) == 0) {
    throw new InvalidMergeQueryException("You need to specify key fields before executing a merge query");
  }

  // In the degenerate case of this query type, we have to run multiple
  // queries as there is no universal single-query mechanism that will work.
  // Our degenerate case is not designed for performance efficiency but
  // for comprehensibility. Any practical database driver will override
  // this method with database-specific logic, so this function serves only
  // as a fallback to aid developers of new drivers.

  // Wrap multiple queries in a transaction, if the database supports it.
  $transaction = $this->connection->startTransaction();

  // Manually check if the record already exists.
  $select = $this->connection->select($this->table);
  foreach ($this->keyFields as $field => $value) {
    $select->condition($field, $value);
  }

  $select = $select->countQuery();
  $sql = (string) $select;
  $arguments = $select->getArguments();
  $num_existing = db_query($sql, $arguments)->fetchField();


  if ($num_existing) {
    // If there is already an existing record, run an update query.

    if ($this->updateFields) {
      $update_fields = $this->updateFields;
    }
    else {
      $update_fields = $this->insertFields;
      // If there are no exclude fields, this is a no-op.
      foreach ($this->excludeFields as $exclude_field) {
        unset($update_fields[$exclude_field]);
      }
    }
    if ($update_fields || $this->expressionFields) {
      // Only run the update if there are no fields or expressions to update.
      $update = $this->connection->update($this->table, $this->queryOptions)->fields($update_fields);
      foreach ($this->keyFields as $field => $value) {
        $update->condition($field, $value);
      }
      foreach ($this->expressionFields as $field => $expression) {
        $update->expression($field, $expression['expression'], $expression['arguments']);
      }
      $update->execute();
    }
  }
  else {
    // If there is no existing record, run an insert query.
    $insert_fields = $this->insertFields + $this->keyFields;
    $this->connection->insert($this->table, $this->queryOptions)->fields($insert_fields)->execute();
  }

  // Transaction commits here where $transaction looses scope.
}
?>