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Added doc notes about how to avoid JSON parsing
Added FAQ too as it has bitten more than one user (see tickets #172, #190).
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@ -189,6 +189,20 @@ the `Json` adapter::
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Reading from the database, |pgjson| values will be automatically converted to
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Reading from the database, |pgjson| values will be automatically converted to
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Python objects.
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Python objects.
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.. note::
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If you are using the PostgreSQL :sql:`json` data type but you want to read
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it as string in Python instead of having it parsed, your can either cast
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the column to :sql:`text` in the query (it is an efficient operation, that
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doesn't involve a copy)::
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cur.execute("select jsondata::text from mytable")
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or you can register a no-op `!loads()` function with
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`register_default_json()`::
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psycopg2.extras.register_default_json(loads=lambda x: x)
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.. note::
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.. note::
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You can use `~psycopg2.extensions.register_adapter()` to adapt any Python
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You can use `~psycopg2.extensions.register_adapter()` to adapt any Python
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@ -204,7 +218,7 @@ Python objects.
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effects.
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effects.
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If you want to customize the adaptation from Python to PostgreSQL you can
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If you want to customize the adaptation from Python to PostgreSQL you can
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either provide a custom `!dumps()` function to `!Json`::
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either provide a custom `!dumps()` function to `Json`::
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curs.execute("insert into mytable (jsondata) values (%s)",
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curs.execute("insert into mytable (jsondata) values (%s)",
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[Json({'a': 100}, dumps=simplejson.dumps)])
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[Json({'a': 100}, dumps=simplejson.dumps)])
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@ -125,6 +125,18 @@ Psycopg converts :sql:`decimal`\/\ :sql:`numeric` database types into Python `!D
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`!psycopg2._psycopg.DECIMAL` instead.
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`!psycopg2._psycopg.DECIMAL` instead.
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.. _faq-json-adapt:
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.. cssclass:: faq
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Psycopg automatically converts PostgreSQL :sql:`json` data into Python objects. How can I receive strings instead?
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The easiest way to avoid JSON parsing is to register a no-op function with
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`~psycopg2.extras.register_default_json()`::
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psycopg2.extras.register_default_json(loads=lambda x: x)
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See :ref:`adapt-json` for further details.
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.. _faq-bytea-9.0:
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.. _faq-bytea-9.0:
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.. cssclass:: faq
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.. cssclass:: faq
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