Class: DBI::BaseStatement

Inherits:
Base
  • Object
show all
Defined in:
lib/dbi/base_classes/statement.rb

Overview

StatementHandles are used to encapsulate the process of managing a statement (DDL or DML) and its parameters, sending it to the database, and gathering any results from the execution of that statement.

As with the other ‘Base` classes, the terms “DBD Required” and “DBD Optional” are defined in DBI::BaseDatabase.

Direct Known Subclasses

DBD::MSSQL::Statement

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(attr = nil) ⇒ BaseStatement

Returns a new instance of BaseStatement.



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# File 'lib/dbi/base_classes/statement.rb', line 14

def initialize(attr=nil)
  @attr = attr || {}
end

Instance Attribute Details

#raise_error ⇒ Object

Returns the value of attribute raise_error.



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# File 'lib/dbi/base_classes/statement.rb', line 12

def raise_error
  @raise_error
end

Instance Method Details

#[](attr) ⇒ Object

Get statement attributes.



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# File 'lib/dbi/base_classes/statement.rb', line 158

def [](attr)
  @attr ||= { }
  @attr[attr]
end

#[]=(attr, value) ⇒ Object

Set statement attributes. DBD Optional.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 166

def []=(attr, value)
  raise NotSupportedError
end

#bind_param(param, value, attribs) ⇒ Object

Bind a parameter to the statement. DBD Required.

The parameter number is named in a hash. This corresponds to the parameter symbols (@param_name) in the statement

The value may be any ruby type. How these are handled is DBD-dependent, but the vast majority of DBDs will convert these to string inside the query.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 28

def bind_param(param, value, attribs)
  raise NotImplementedError
end

#bind_params(bindvars) ⇒ Object

Take a list of bind variables and bind them successively using bind_param.



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# File 'lib/dbi/base_classes/statement.rb', line 73

def bind_params(bindvars)
  bindvars.each {|k, v| bind_param(k, v, nil) }
  self
end

#cancel ⇒ Object

Cancel any result cursors. DBD Optional, but intentionally does not raise any exception as it’s used internally to maintain consistency.



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# File 'lib/dbi/base_classes/statement.rb', line 82

def cancel
end

#column_info ⇒ Object

returns result-set column information as array of hashs, where each hash represents one column. See BaseDatabase#columns. DBD Required.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 62

def column_info
  raise NotImplementedError
end

#execute ⇒ Object

Execute the statement with the known binds. DBD Required.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 35

def execute
  raise NotImplementedError
end

#fetch ⇒ Object

Fetch the next row in the result set. DBD Required.

DBI::Row is responsible for formatting the data the DBD provides it.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 53

def fetch
  raise NotImplementedError
end

#fetch_all ⇒ Object

Fetch all available rows. Result is Array of DBI::Row.



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# File 'lib/dbi/base_classes/statement.rb', line 140

def fetch_all
  rows = []
  loop do
    row = fetch
    break if row.nil?
    rows << row.dup
  end

  if rows.empty?
    nil
  else
    rows
  end
end

#fetch_many(cnt) ⇒ Object

fetch x rows. The result is Array of DBI::Row.



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# File 'lib/dbi/base_classes/statement.rb', line 122

def fetch_many(cnt)
  rows = []
  cnt.times do
    row = fetch
    break if row.nil?
    rows << row.dup
  end

  if rows.empty?
    nil
  else
    rows
  end
end

#fetch_scroll(direction, offset) ⇒ Object

fetch_scroll is provided with a direction and offset and works similar to how seek() is used on files.

The constants available for direction are as follows:

  • SQL_FETCH_NEXT: fetch the next result.

  • SQL_FETCH_LAST: fetch the last result, period.

  • SQL_FETCH_RELATIVE: fetch the result at the offset.

Other constants can be used, but if this method is not supplied by the driver, they will result in a raise of DBI::NotSupportedError.



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# File 'lib/dbi/base_classes/statement.rb', line 99

def fetch_scroll(direction, offset)
  case direction
    when SQL_FETCH_NEXT
      return fetch
    when SQL_FETCH_LAST
      last_row = nil
      while (row=fetch) != nil
        last_row = row
      end
      return last_row
    when SQL_FETCH_RELATIVE
      raise NotSupportedError if offset <= 0
      row = nil
      offset.times { row = fetch; break if row.nil? }
      return row
    else
      raise NotSupportedError
  end
end

#finish ⇒ Object

Close the statement and any result cursors. DBD Required.

Note

Most implementations will fail miserably if you forget to finish your statement handles.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 44

def finish
  raise NotImplementedError
end