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Added documentation for the bytea parser

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This commit is contained in:
Daniele Varrazzo 2011-03-26 11:19:01 +00:00
parent e0cd6f0f00
commit da58bee70a
3 changed files with 17 additions and 12 deletions
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2
NEWS
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@ -1,6 +1,8 @@
What's new in psycopg 2.4.1
---------------------------
- Use own parser for bytea output, not requiring anymore the libpq 9.0
to parse the hex format.
- Correctly detect an empty query sent to the backend (ticket #46).

4
doc/src/faq.rst
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@ -97,7 +97,9 @@ Psycopg converts :sql:`decimal`\/\ :sql:`numeric` database types into Python `!D
Transferring binary data from PostgreSQL 9.0 doesn't work.
PostgreSQL 9.0 uses by default `the "hex" format`__ to transfer
:sql:`bytea` data: the format can't be parsed by the libpq 8.4 and
earlier. Three options to solve the problem are:
earlier. The problem is solved in Psycopg 2.4.1, that uses its own parser
for the :sql:`bytea` format. For previous Psycopg releases, three options
to solve the problem are:
- set the bytea_output__ parameter to ``escape`` in the server;
- execute the database command ``SET bytea_output TO escape;`` in the

23
doc/src/usage.rst
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@ -271,6 +271,10 @@ the SQL string that would be sent to the database.
.. versionchanged:: 2.4
only strings were supported before.
.. versionchanged:: 2.4.1
can parse the 'hex' format from 9.0 servers without relying on the
version of the client library.
.. note::
In Python 2, if you have binary data in a `!str` object, you can pass them
@ -282,18 +286,15 @@ the SQL string that would be sent to the database.
.. warning::
PostgreSQL 9 uses by default `a new "hex" format`__ to emit :sql:`bytea`
fields. Unfortunately this format can't be parsed by libpq versions
before 9.0. This means that using a library client with version lesser
than 9.0 to talk with a server 9.0 or later you may have problems
receiving :sql:`bytea` data. To work around this problem you can set the
`bytea_output`__ parameter to ``escape``, either in the server
configuration or in the client session using a query such as ``SET
bytea_output TO escape;`` before trying to receive binary data.
Since version 9.0 PostgreSQL uses by default `a new "hex" format`__ to
emit :sql:`bytea` fields. Starting from Psycopg 2.4.1 the format is
correctly supported. If you use a previous version you will need some
extra care when receiving bytea from PostgreSQL: you must have at least
the libpq 9.0 installed on the client or alternatively you can set the
`bytea_output`__ configutation parameter to ``escape``, either in the
server configuration file or in the client session (using a query such as
``SET bytea_output TO escape;``) before receiving binary data.
Starting from Psycopg 2.4 this condition is detected and signaled with a
`~psycopg2.InterfaceError`.
.. __: http://www.postgresql.org/docs/9.0/static/datatype-binary.html
.. __: http://www.postgresql.org/docs/9.0/static/runtime-config-client.html#GUC-BYTEA-OUTPUT