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Modify COPY FROM to match the null-value string against the column value

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before it is de-backslashed, not after.  This allows the null string \N
to be reliably distinguished from the data value \N (which must be
represented as \\N).  Per bug report from Manfred Koizar ... but it's
amazing this hasn't been reported before ...
Also, be consistent about encoding conversion for null string: the form
specified in the command is in the server encoding, but what is sent
to/from client must be in client encoding.  This never worked quite
right before either.
This commit is contained in:
Tom Lane
2003-10-06 02:38:53 +00:00
parent 351adb8dfb
commit 0eceaaf9b7
2 changed files with 62 additions and 30 deletions
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23
doc/src/sgml/ref/copy.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.52 2003/09/30 01:56:11 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.53 2003/10/06 02:38:53 tgl Exp $
PostgreSQL documentation
-->
@ -257,7 +257,7 @@ COPY <replaceable class="parameter">tablename</replaceable> [ ( <replaceable cla
Columns in a row are separated by the delimiter character.
The column values themselves are strings generated by the
output function, or acceptable to the input function, of each
attribute's data type. The specified null-value string is used in
attribute's data type. The specified null string is used in
place of columns that are null.
<command>COPY FROM</command> will raise an error if any line of the
input file contains more or fewer columns than are expected.
@ -282,6 +282,15 @@ COPY <replaceable class="parameter">tablename</replaceable> [ ( <replaceable cla
newline, carriage return, and the current delimiter character.
</para>
<para>
The specified null string is sent by <command>COPY TO</command> without
adding any backslashes; conversely, <command>COPY FROM</command> matches
the input against the null string before removing backslashes. Therefore,
a null string such as <literal>\N</literal> cannot be confused with
the actual data value <literal>\N</literal> (which would be represented
as <literal>\\N</literal>).
</para>
<para>
The following special backslash sequences are recognized by
<command>COPY FROM</command>:
@ -335,10 +344,12 @@ COPY <replaceable class="parameter">tablename</replaceable> [ ( <replaceable cla
</para>
<para>
Never put a backslash before a data character <literal>N</> or period
(<literal>.</>). Such pairs will be mistaken for the default null string
or the end-of-data marker, respectively. Any other backslashed character
that is not mentioned in the above table will be taken to represent itself.
Any other backslashed character that is not mentioned in the above table
will be taken to represent itself. However, beware of adding backslashes
unnecessarily, since that might accidentally produce a string matching the
end-of-data marker (<literal>\.</>) or the null string (<literal>\N</> by
default). These strings will be recognized before any other backslash
processing is done.
</para>
<para>