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Completed documentation for the COPY-related methods.
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Daniele Varrazzo
Federico Di Gregorio
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@ -339,42 +339,67 @@ The ``cursor`` class
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This method currently does nothing but it is safe to call it.
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.. method:: copy_from(file, table, sep='\\t', null='\\N', columns=None)
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Read data *from* the file-like object :obj:`file` appending them to
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the table named :obj:`table`. :obj:`file` must have both ``read()``
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and ``readline()`` method. See :ref:`copy` for an overview. ::
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>>> f = StringIO("42\tfoo\n74\tbar\n")
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>>> cur.copy_from(f, 'test', columns=('num', 'data'))
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>>> cur.execute("select * from test where id > 5;")
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>>> cur.fetchall()
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[(7, 42, 'foo'), (8, 74, 'bar')]
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The optional argument :obj:`sep` is the columns separator and
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:obj:`null` represents ``NULL`` values in the file.
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The :obj:`columns` argument is a sequence of field names: if not
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``None`` only the specified fields will be included in the dump.
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.. versionchanged:: 2.0.6
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added the :obj:`columns` parameter.
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.. method:: copy_to(file, table, sep='\\t', null='\\N', columns=None)
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Write the content of the table named :obj:`table` *to* the file-like object :obj:`file`. :obj:`file` must have a ``write()`` method. See
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:ref:`copy` for an overview. ::
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>>> cur.copy_to(sys.stdout, 'test', sep="|")
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1|100|abc'def
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2|\N|dada
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The optional argument :obj:`sep` is the columns separator and
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:obj:`null` represents ``NULL`` values in the file.
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The :obj:`columns` argument is a sequence representing the fields
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where the read data will be entered. Its length and column type should
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match the content of the read file.
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.. versionchanged:: 2.0.6
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added the :obj:`columns` parameter.
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.. method:: copy_expert(sql, file [, size])
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Submit a user-composed COPY statement.
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Submit a user-composed ``COPY`` statement. The method is useful to
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handle all the parameters that PostgreSQL makes available (see
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|COPY|__ command documentation).
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>>> cur.copy_expert("COPY test TO STDOUT WITH CSV HEADER", sys.stdout)
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id,num,data
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1,100,abc'def
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2,,dada
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:obj:`file` must be an open, readable file for ``COPY FROM`` or an
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open, writeable file for ``COPY TO``. The optional :obj:`size`
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argument, when specified for a ``COPY FROM`` statement, will be passed
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to file's read method to control the read buffer size.
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to file's read method to control the read buffer size.
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.. todo::
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.. |COPY| replace:: ``COPY``
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.. __: http://www.postgresql.org/docs/8.4/static/sql-copy.html
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I'm sure copy_expert can be described better!
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.. method:: copy_from(file, table, sep='\t', null='\N', columns=None)
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Read data *from* the file-like object :obj:`file` appending them to
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the table named :obj:`table`. See :ref:`copy`.
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:obj:`file` must have both ``read()`` and ``readline()`` method.
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The optional arguments: :obj:`sep` is the columns separator and
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:obj:`null` represents ``NULL`` values in the file.
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.. todo:: columns argument in copy_from
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.. method:: copy_to(file, table, sep='\t', null='\N', columns=None)
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Write the content of the table named :obj:`table` *to* the file-like
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object :obj:`file`. See :ref:`copy`.
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:obj:`file` must have a ``write()`` method.
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The optional arguments: :obj:`sep` is the columns separator and
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:obj:`null` represents ``NULL`` values in the file.
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.. todo:: columns argument in copy_to
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.. versionadded:: 2.0.6
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.. attribute:: row_factory
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@ -339,19 +339,26 @@ Using COPY TO and COPY FROM
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---------------------------
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Psycopg :class:`cursor` objects provide an interface to the efficient
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PostgreSQL `COPY command`_ to move data from files to tables and back.
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PostgreSQL |COPY|__ command to move data from files to tables and back.
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The methods exposed are:
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The :meth:`cursor.copy_to()` method writes the content of a table *to* a
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file-like object. The target file must have a ``write()`` method.
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:meth:`cursor.copy_to()`
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Writes the content of a table *to* a file-like object (``COPY table TO
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file`` syntax). The target file must have a ``write()`` method.
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The :meth:`cursor.copy_from()` reads data *from* a file-like object appending
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them to a database table. The source file must have both ``read()`` and
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``readline()`` method.
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:meth:`cursor.copy_from()`
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Reads data *from* a file-like object appending them to a database table
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(``COPY table FROM file`` syntax). The source file must have both
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``read()`` and ``readline()`` method.
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Both methods accept two optional arguments: ``sep`` (defaulting to a tab) is
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the columns separator and ``null`` (defaulting to ``\N``) represents ``NULL``
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values in the file.
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:meth:`cursor.copy_expert()`
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Allows to handle more specific cases and to use all the |COPY| features
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available in PostgreSQL.
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.. _COPY command: http://www.postgresql.org/docs/8.4/static/sql-copy.html
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Please refer to the documentation of the single methods for details and
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examples.
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.. |COPY| replace:: ``COPY``
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.. __: http://www.postgresql.org/docs/8.4/static/sql-copy.html
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