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Add missing_ok option to the SQL functions for reading files.

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This makes it possible to use the functions without getting errors, if there
is a chance that the file might be removed or renamed concurrently.
pg_rewind needs to do just that, although this could be useful for other
purposes too. (The changes to pg_rewind to use these functions will come in
a separate commit.)

The read_binary_file() function isn't very well-suited for extensions.c's
purposes anymore, if it ever was. So bite the bullet and make a copy of it
in extension.c, tailored for that use case. This seems better than the
accidental code reuse, even if it's a some more lines of code.

Michael Paquier, with plenty of kibitzing by me.
This commit is contained in:
Heikki Linnakangas
2015-06-28 21:35:46 +03:00
parent cca8ba9529
commit cb2acb1081
6 changed files with 274 additions and 102 deletions
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42
doc/src/sgml/func.sgml
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@ -17811,43 +17811,63 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
<tbody>
<row>
<entry>
<literal><function>pg_ls_dir(<parameter>dirname</> <type>text</>)</function></literal>
<literal><function>pg_ls_dir(<parameter>dirname</> <type>text</> [, <parameter>missing_ok</> <type>boolean</>, <parameter>include_dot_dirs</> <type>boolean</>])</function></literal>
</entry>
<entry><type>setof text</type></entry>
<entry>List the contents of a directory</entry>
<entry>
List the contents of a directory.
</entry>
</row>
<row>
<entry>
<literal><function>pg_read_file(<parameter>filename</> <type>text</> [, <parameter>offset</> <type>bigint</>, <parameter>length</> <type>bigint</>])</function></literal>
<literal><function>pg_read_file(<parameter>filename</> <type>text</> [, <parameter>offset</> <type>bigint</>, <parameter>length</> <type>bigint</> [, <parameter>missing_ok</> <type>boolean</>] ])</function></literal>
</entry>
<entry><type>text</type></entry>
<entry>Return the contents of a text file</entry>
<entry>
Return the contents of a text file.
</entry>
</row>
<row>
<entry>
<literal><function>pg_read_binary_file(<parameter>filename</> <type>text</> [, <parameter>offset</> <type>bigint</>, <parameter>length</> <type>bigint</>])</function></literal>
<literal><function>pg_read_binary_file(<parameter>filename</> <type>text</> [, <parameter>offset</> <type>bigint</>, <parameter>length</> <type>bigint</> [, <parameter>missing_ok</> <type>boolean</>] ])</function></literal>
</entry>
<entry><type>bytea</type></entry>
<entry>Return the contents of a file</entry>
<entry>
Return the contents of a file.
</entry>
</row>
<row>
<entry>
<literal><function>pg_stat_file(<parameter>filename</> <type>text</>)</function></literal>
<literal><function>pg_stat_file(<parameter>filename</> <type>text</>[, <parameter>missing_ok</> <type>boolean</type>])</function></literal>
</entry>
<entry><type>record</type></entry>
<entry>Return information about a file</entry>
<entry>
Return information about a file.
</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
All of these functions take an optional <parameter>missing_ok</> parameter,
which specifies the behaviour when the file or directory does not exist.
If <literal>true</literal>, the function returns NULL (except
<function>pg_ls_dir</>, which returns an empty result set). If
<literal>false</>, an error is raised. The default is <literal>false</>.
</para>
<indexterm>
<primary>pg_ls_dir</primary>
</indexterm>
<para>
<function>pg_ls_dir</> returns all the names in the specified
directory, except the special entries <quote><literal>.</></> and
<quote><literal>..</></>.
<function>pg_ls_dir</> returns the names of all files (and directories
and other special files) in the specified directory. The <parameter>
include_dot_dirs</> indicates whether <quote>.</> and <quote>..</> are
included in the result set. The default is to exclude them
(<literal>false/>), but including them can be useful when
<parameter>missing_ok</> is <literal>true</literal>, to distinguish an
empty directory from an non-existent directory.
</para>
<indexterm>