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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.
REL7_4_STABLE
Tom Lane 22 years ago
parent 351adb8dfb
commit 0eceaaf9b7
2 changed files with 62 additions and 30 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 23
      doc/src/sgml/ref/copy.sgml
  2. 69
      src/backend/commands/copy.c

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>

69
src/backend/commands/copy.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.212 2003/09/29 22:06:40 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.213 2003/10/06 02:38:53 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -122,7 +122,7 @@ static StringInfoData attribute_buf;
* to server encoding, and then extract individual attribute fields into
* attribute_buf. (We used to have CopyReadAttribute read the input source
* directly, but that caused a lot of encoding issues and unnecessary logic
* complexity).
* complexity.)
*/
static StringInfoData line_buf;
static bool line_buf_converted;
@ -133,7 +133,8 @@ static void CopyTo(Relation rel, List *attnumlist, bool binary, bool oids,
static void CopyFrom(Relation rel, List *attnumlist, bool binary, bool oids,
char *delim, char *null_print);
static bool CopyReadLine(void);
static char *CopyReadAttribute(const char *delim, CopyReadResult *result);
static char *CopyReadAttribute(const char *delim, const char *null_print,
CopyReadResult *result, bool *isnull);
static Datum CopyReadBinaryAttribute(int column_no, FmgrInfo *flinfo,
Oid typelem, bool *isnull);
static void CopyAttributeOut(char *string, char *delim);
@ -1014,6 +1015,17 @@ CopyTo(Relation rel, List *attnumlist, bool binary, bool oids,
tmp = 0;
CopySendInt32(tmp);
}
else
{
/*
* For non-binary copy, we need to convert null_print to client
* encoding, because it will be sent directly with CopySendString.
*/
if (server_encoding != client_encoding)
null_print = (char *)
pg_server_to_client((unsigned char *) null_print,
strlen(null_print));
}
mySnapshot = CopyQuerySnapshot();
@ -1441,9 +1453,10 @@ CopyFrom(Relation rel, List *attnumlist, bool binary, bool oids,
if (file_has_oids)
{
string = CopyReadAttribute(delim, &result);
string = CopyReadAttribute(delim, null_print,
&result, &isnull);
if (strcmp(string, null_print) == 0)
if (isnull)
ereport(ERROR,
(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
errmsg("null OID in COPY data")));
@ -1478,9 +1491,10 @@ CopyFrom(Relation rel, List *attnumlist, bool binary, bool oids,
errmsg("missing data for column \"%s\"",
NameStr(attr[m]->attname))));
string = CopyReadAttribute(delim, &result);
string = CopyReadAttribute(delim, null_print,
&result, &isnull);
if (strcmp(string, null_print) == 0)
if (isnull)
{
/* we read an SQL NULL, no need to do anything */
}
@ -1880,25 +1894,33 @@ CopyReadLine(void)
return result;
}
/*
/*----------
* Read the value of a single attribute, performing de-escaping as needed.
*
* delim is the column delimiter string (must be just one byte for now).
* null_print is the null marker string. Note that this is compared to
* the pre-de-escaped input string.
*
* *result is set to indicate what terminated the read:
* NORMAL_ATTR: column delimiter
* END_OF_LINE: end of line
* In either case, the string read up to the terminator is returned.
*
* Note: This function does not care about SQL NULL values -- it
* is the caller's responsibility to check if the returned string
* matches what the user specified for the SQL NULL value.
*
* delim is the column delimiter string.
* *isnull is set true or false depending on whether the input matched
* the null marker. Note that the caller cannot check this since the
* returned string will be the post-de-escaping equivalent, which may
* look the same as some valid data string.
*----------
*/
static char *
CopyReadAttribute(const char *delim, CopyReadResult *result)
CopyReadAttribute(const char *delim, const char *null_print,
CopyReadResult *result, bool *isnull)
{
char c;
char delimc = delim[0];
int start_cursor = line_buf.cursor;
int end_cursor;
int input_len;
/* reset attribute_buf to empty */
attribute_buf.len = 0;
@ -1909,6 +1931,7 @@ CopyReadAttribute(const char *delim, CopyReadResult *result)
for (;;)
{
end_cursor = line_buf.cursor;
if (line_buf.cursor >= line_buf.len)
break;
c = line_buf.data[line_buf.cursor++];
@ -1957,16 +1980,6 @@ CopyReadAttribute(const char *delim, CopyReadResult *result)
c = val & 0377;
}
break;
/*
* This is a special hack to parse `\N' as
* <backslash-N> rather then just 'N' to provide
* compatibility with the default NULL output. -- pe
*/
case 'N':
appendStringInfoCharMacro(&attribute_buf, '\\');
c = 'N';
break;
case 'b':
c = '\b';
break;
@ -1993,6 +2006,14 @@ CopyReadAttribute(const char *delim, CopyReadResult *result)
appendStringInfoCharMacro(&attribute_buf, c);
}
/* check whether raw input matched null marker */
input_len = end_cursor - start_cursor;
if (input_len == strlen(null_print) &&
strncmp(&line_buf.data[start_cursor], null_print, input_len) == 0)
*isnull = true;
else
*isnull = false;
return attribute_buf.data;
}

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