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Added docs about the usability of sql objects with copy_expert()

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See issue #529.
This commit is contained in:
Daniele Varrazzo 2017-03-16 00:12:13 +00:00
parent 3bfbd3a0a5
commit c7f5690426
3 changed files with 15 additions and 6 deletions
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5
doc/src/cursor.rst
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@ -601,7 +601,10 @@ The ``cursor`` class
The *sql* statement should be in the form :samp:`COPY {table} TO
STDOUT` to export :samp:`{table}` to the *file* object passed as
argument or :samp:`COPY {table} FROM STDIN` to import the content of
the *file* object into :samp:`{table}`.
the *file* object into :samp:`{table}`. If you need to compose a
:sql:`COPY` statement dynamically (because table, fields, or query
parameters are in Python variables) you may use the objects provided
by the `psycopg2.sql` module.
*file* must be a readable file-like object (as required by
`~cursor.copy_from()`) for *sql* statement :sql:`COPY ... FROM STDIN`

5
doc/src/sql.rst
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@ -55,6 +55,11 @@ from the query parameters::
.format(sql.Identifier('my_table')),
[10, 20])
The objects exposed by the `!sql` module can be used to compose a query as a
Python string (using the `~Composable.as_string()` method) or passed directly
to cursor methods such as `~cursor.execute()`, `~cursor.executemany()`,
`~cursor.copy_expert()`.
.. autoclass:: Composable

11
lib/sql.py
View File

@ -36,8 +36,9 @@ class Composable(object):
"""
Abstract base class for objects that can be used to compose an SQL string.
`!Composable` objects can be passed directly to `~cursor.execute()` and
`~cursor.executemany()` in place of the query string.
`!Composable` objects can be passed directly to `~cursor.execute()`,
`~cursor.executemany()`, `~cursor.copy_expert()` in place of the query
string.
`!Composable` objects can be joined using the ``+`` operator: the result
will be a `Composed` instance containing the objects joined. The operator
@ -58,9 +59,9 @@ class Composable(object):
:param context: the context to evaluate the string into.
:type context: `connection` or `cursor`
The method is automatically invoked by `~cursor.execute()` and
`~cursor.executemany()` if a `!Composable` is passed instead of the
query string.
The method is automatically invoked by `~cursor.execute()`,
`~cursor.executemany()`, `~cursor.copy_expert()` if a `!Composable` is
passed instead of the query string.
"""
raise NotImplementedError