Class: DBI::StatementHandle

Inherits:
Handle
  • Object
show all
Includes:
Enumerable
Defined in:
lib/dbi/handles/statement.rb

Overview

StatementHandle is the interface the consumer sees after successfully issuing a DatabaseHandle#prepare. They may also be exposed through other methods that send statements to the database.

Almost all methods in this class will raise InterfaceError if the statement is already finished.

Instance Attribute Summary collapse

Attributes inherited from Handle

#convert_types, #handle, #trace_mode, #trace_output

Instance Method Summary collapse

Methods inherited from Handle

#func, #trace

Constructor Details

#initialize(handle, fetchable = false, prepared = true, convert_types = true, executed = false) ⇒ StatementHandle

Returns a new instance of StatementHandle.



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# File 'lib/dbi/handles/statement.rb', line 17

def initialize(handle, fetchable=false, prepared=true, convert_types=true, executed=false)
  super(handle)
  @fetchable = fetchable
  @prepared  = prepared     # only false if immediate execute was used
  @executed  = executed     # only true if the statement was already executed.
  @cols = nil
  @coltypes = nil
  @convert_types = convert_types

  if @fetchable
    @row = DBI::Row.new(column_names, column_types, nil, @convert_types)
  else
    @row = nil
  end
end

Instance Attribute Details

#dbh ⇒ Object

Returns the value of attribute dbh.



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

def dbh
  @dbh
end

#raise_error ⇒ Object

Returns the value of attribute raise_error.



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# File 'lib/dbi/handles/statement.rb', line 15

def raise_error
  @raise_error
end

Instance Method Details

#[](attr) ⇒ Object

Get an attribute from the StatementHandle object.



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# File 'lib/dbi/handles/statement.rb', line 358

def [] (attr)
  sanity_check
  @handle[attr]
end

#[]=(attr, val) ⇒ Object

Set an attribute on the StatementHandle object.



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# File 'lib/dbi/handles/statement.rb', line 364

def []= (attr, val)
  sanity_check
  @handle[attr] = val
end

#bind_coltype(pos, type) ⇒ Object

Instruct successive calls to #fetch to cast the type returned into ‘type`, for row position `pos`. Like all bind_* calls, `pos` indexes starting at 1.

‘type` is an object with the DBI::Type calling convention.

This call must be called after #execute has successfully ran, otherwise it will raise InterfaceError.

Example:

# `foo` is an integer and this statement will return two rows.
sth = dbh.prepare("select foo from bar")
# would raise InterfaceError if called here
sth.execute

sth.bind_coltype(1, DBI::Type::Varchar)
# would normally use DBI::Type::Integer and return a Fixnum. We'll make it a string.
sth.fetch => ["1"]

# Here we coerce it to Float.
sth.bind_coltype(1, DBI::Type::Float)
sth.fetch => [1.0]
sth.finish



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# File 'lib/dbi/handles/statement.rb', line 72

def bind_coltype(pos, type)
  sanity_check({:prepared => true, :executed => true})

  coltypes = column_types

  if (pos - 1) < 1
    raise InterfaceError, "bind positions index starting at 1"
  end

  coltypes[pos-1] = type
  @row = DBI::Row.new(column_names, coltypes, nil, @convert_types)
end

#bind_param(param, value, attribs = nil) ⇒ Object

Just like BaseStatement#bind_param, but will attempt to convert the type if it’s supposed to, adhering to the DBD’s current ruleset.



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# File 'lib/dbi/handles/statement.rb', line 89

def bind_param(param, value, attribs=nil)
  sanity_check({ :prepared => true })

  if @convert_types
    value = DBI::Utils::ConvParam.conv_param(dbh.driver_name, value)[0]
  end

  @handle.bind_param(param, value, attribs)
end

#cancel ⇒ Object

Cancel the query, closing any open result cursors and truncating any result sets.

The difference between this and #finish is that cancelled statements may be re-executed.



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# File 'lib/dbi/handles/statement.rb', line 146

def cancel
  sanity_check
  @handle.cancel if @fetchable
  @fetchable = false
end

#column_info ⇒ Object

See BaseStatement#column_info.



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# File 'lib/dbi/handles/statement.rb', line 183

def column_info
  sanity_check
  @handle.column_info.collect {|col| ColumnInfo.new(col) }
end

#column_names ⇒ Object

Obtains the column names for this query as an array.



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# File 'lib/dbi/handles/statement.rb', line 155

def column_names
  sanity_check
  return @cols unless @cols.nil?
  @cols = @handle.column_info.collect {|col| col['name'] }
end

#column_types ⇒ Object

Obtain the type mappings for the columns in this query based on ColumnInfo data on the query.

The result will be a position-dependent array of objects that conform to the DBI::Type calling syntax.



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# File 'lib/dbi/handles/statement.rb', line 168

def column_types
  sanity_check
  return @coltypes unless @coltypes.nil?
  @coltypes = @handle.column_info.collect do |col|
    if col['dbi_type']
      col['dbi_type']
    else
      DBI::TypeUtil.type_name_to_module(col['type_name'])
    end
  end
end

#each(&p) ⇒ Object

Synonym for #fetch with a block.

Raises:



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# File 'lib/dbi/handles/statement.rb', line 236

def each(&p)
  sanity_check({:fetchable => true, :prepared => true, :executed => true})
  raise InterfaceError, "No block given" unless block_given?

  fetch(&p)
end

#execute(bindvars = {}) ⇒ Object

Execute the statement.

This generally means that the statement will be sent to the database and some form of result cursor will be obtained, but is ultimately driver-dependent.

If arguments are supplied, these are fed to #bind_param.



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# File 'lib/dbi/handles/statement.rb', line 107

def execute(bindvars={})
  cancel     # cancel before
  sanity_check({:prepared => true })

  if @convert_types
      bindvars = DBI::Utils::ConvParam.conv_param(dbh.driver_name, bindvars)
  end

  @handle.bind_params(bindvars)
  @handle.execute
  @fetchable = true
  @executed = true

  # TODO:?
  #if @row.nil?
  @row = DBI::Row.new(column_names, column_types, nil, @convert_types)
  #end
  return nil
end

#fetch(&p) ⇒ Object

See BaseStatement#fetch.

fetch can also take a block which will be applied to each row in a similar fashion to Enumerable#collect. See #each.



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# File 'lib/dbi/handles/statement.rb', line 207

def fetch(&p)
  sanity_check({ :fetchable => true, :prepared => true, :executed => true })

  if block_given?
    while (res = @handle.fetch) != nil
      @row = @row.dup
      @row.set_values(res)
      yield @row
    end
    @handle.cancel
    @fetchable = false
    return nil
  else
    res = @handle.fetch
    if res.nil?
      @handle.cancel
      @fetchable = false
    else
      @row = @row.dup
      @row.set_values(res)
      res = @row
    end
    return res
  end
end

#fetch_all ⇒ Object

Fetch the entire result set. Result is array of DBI::Row.



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# File 'lib/dbi/handles/statement.rb', line 321

def fetch_all
  sanity_check({:fetchable => true, :prepared => true, :executed => true})

  cols = column_names
  fetched_rows = []

  begin
    while row = fetch do
      fetched_rows.push(row)
    end
  rescue Exception
  end

  @handle.cancel
  @fetchable = false

  return fetched_rows
end

#fetch_array ⇒ Object

Similar to #fetch, but returns Array of Array instead of Array of DBI::Row objects (and therefore does not perform type mapping). This is basically a way to get the raw data from the DBD.



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# File 'lib/dbi/handles/statement.rb', line 248

def fetch_array
  sanity_check({:fetchable => true, :prepared => true, :executed => true})

  if block_given?
    while (res = @handle.fetch) != nil
      yield res
    end
    @handle.cancel
    @fetchable = false
    return nil
  else
    res = @handle.fetch
    if res.nil?
      @handle.cancel
      @fetchable = false
    end
    return res
  end
end

#fetch_hash ⇒ Object

Map the columns and results into an Array of Hash resultset.

No type conversion is performed here. Expect this to change in 0.6.0.



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# File 'lib/dbi/handles/statement.rb', line 273

def fetch_hash
  sanity_check({:fetchable => true, :prepared => true, :executed => true})

  cols = column_names

  if block_given?
    while (row = @handle.fetch) != nil
      hash = {}
      row.each_with_index {|v, i| hash[cols[i]] = v}
      yield hash
    end
    @handle.cancel
    @fetchable = false
    return nil
  else
    row = @handle.fetch
    if row.nil?
      @handle.cancel
      @fetchable = false
      return nil
    else
      hash = {}
      row.each_with_index {|v, i| hash[cols[i]] = v}
      return hash
    end
  end
end

#fetch_many(cnt) ⇒ Object

Fetch ‘cnt` rows. Result is array of DBI::Row



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# File 'lib/dbi/handles/statement.rb', line 304

def fetch_many(cnt)
  sanity_check({:fetchable => true, :prepared => true, :executed => true})

  cols = column_names
  rows = @handle.fetch_many(cnt)
  if rows.nil? or rows.empty?
    @handle.cancel
    @fetchable = false
    return []
  else
    return rows.collect{|r| tmp = @row.dup; tmp.set_values(r); tmp }
  end
end

#fetch_scroll(direction, offset = 1) ⇒ Object

See BaseStatement#fetch_scroll.



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# File 'lib/dbi/handles/statement.rb', line 343

def fetch_scroll(direction, offset=1)
  sanity_check({:fetchable => true, :prepared => true, :executed => true})

  row = @handle.fetch_scroll(direction, offset)
  if row.nil?
    #@handle.cancel
    #@fetchable = false
    return nil
  else
    @row.set_values(row)
    return @row
  end
end

#fetchable? ⇒ Boolean

Returns true if the statement is believed to return data upon #fetch.

The current reliability of this (and the concept in general) is suspect.

Returns:

  • (Boolean) 


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# File 'lib/dbi/handles/statement.rb', line 43

def fetchable?
  @fetchable
end

#finish ⇒ Object

Finish the statement, causing the database to release all assets related to it (any result cursors, normally).

StatementHandles that have already been finished will normally be inoperable and unavailable for further use.



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# File 'lib/dbi/handles/statement.rb', line 134

def finish
  sanity_check
  @handle.finish
  @handle = nil
end

#finished? ⇒ Boolean

Returns true if the StatementHandle has had #finish called on it, explicitly or otherwise.

Returns:

  • (Boolean) 


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

def finished?
  @handle.nil?
end

#rows ⇒ Object

Should return the row modified count as the result of statement execution.

However, some low-level drivers do not supply this information or supply misleading information (> 0 rows for read-only select statements, f.e.)



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# File 'lib/dbi/handles/statement.rb', line 195

def rows
  sanity_check
  @handle.rows
end