public function Schema::calculateClusteredIndexRowSizeBytes in Drupal driver for SQL Server and SQL Azure 4.0.x

Same name and namespace in other branches

1. 4.2.x src/Driver/Database/sqlsrv/Schema.php \Drupal\sqlsrv\Driver\Database\sqlsrv\Schema::calculateClusteredIndexRowSizeBytes()
2. 3.1.x src/Driver/Database/sqlsrv/Schema.php \Drupal\sqlsrv\Driver\Database\sqlsrv\Schema::calculateClusteredIndexRowSizeBytes()
3. 4.1.x src/Driver/Database/sqlsrv/Schema.php \Drupal\sqlsrv\Driver\Database\sqlsrv\Schema::calculateClusteredIndexRowSizeBytes()

Estimates the row size of a clustered index.

See also

https://msdn.microsoft.com/en-us/library/ms178085.aspx

2 calls to Schema::calculateClusteredIndexRowSizeBytes()

Schema::addIndex in src/Driver/Database/sqlsrv/Schema.php

Add an index.

Schema::createPrimaryKey in src/Driver/Database/sqlsrv/Schema.php

Create primary key.

File

src/Driver/Database/sqlsrv/Schema.php, line 1172

Class

Schema

Namespace

Drupal\sqlsrv\Driver\Database\sqlsrv

Code

public function calculateClusteredIndexRowSizeBytes($table, $fields, $unique = TRUE) {

  // The fields must already be in the database to retrieve their real size.
  $info = $this
    ->queryColumnInformation($table);

  // Specify the number of fixed-length and variable-length columns
  // and calculate the space that is required for their storage.
  $num_cols = count($fields);
  $num_variable_cols = 0;
  $max_var_size = 0;
  $max_fixed_size = 0;
  foreach ($fields as $field) {
    if ($this
      ->isVariableLengthType($info['columns'][$field]['type'])) {
      $num_variable_cols++;
      $max_var_size += $info['columns'][$field]['max_length'];
    }
    else {
      $max_fixed_size += $info['columns'][$field]['max_length'];
    }
  }

  // If the clustered index is nonunique, account for the uniqueifier column.
  if (!$unique) {
    $num_cols++;
    $num_variable_cols++;
    $max_var_size += 4;
  }

  // Part of the row, known as the null bitmap, is reserved to manage column
  // nullability. Calculate its size.
  $null_bitmap = 2 + ($num_cols + 7) / 8;

  // Calculate the variable-length data size.
  $variable_data_size = empty($num_variable_cols) ? 0 : 2 + $num_variable_cols * 2 + $max_var_size;

  // Calculate total row size.
  $row_size = $max_fixed_size + $variable_data_size + $null_bitmap + 4;
  return $row_size;
}