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Modify COPY TO to emit carriage returns and newlines as backslash escapes
(backslash-r, backslash-n) for protection against newline-conversion munging. In future we will also tweak COPY FROM, but this part of the change should be backwards-compatible. Per pghackers discussion. Also, update COPY reference page to describe the backslash conversions more completely and accurately.
This commit is contained in:
Tom Lane
parent
c16ef167df
commit
9832a235c5
@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.27 2002/01/20 22:19:56 petere Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.28 2002/02/12 21:25:34 tgl Exp $
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PostgreSQL documentation
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-->
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@ -74,7 +74,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
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<term><replaceable class="parameter">filename</replaceable></term>
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<listitem>
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<para>
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The absolute Unix file name of the input or output file.
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The absolute Unix path name of the input or output file.
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</para>
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</listitem>
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</varlistentry>
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@ -225,7 +225,7 @@ ERROR: <replaceable>reason</replaceable>
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By default, a text copy uses a tab ("\t") character as a delimiter
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between fields. The field delimiter may be changed to any other single
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character with the keyword phrase USING DELIMITERS. Characters
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in data fields which happen to match the delimiter character will
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in data fields that happen to match the delimiter character will
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be backslash quoted.
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</para>
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@ -265,8 +265,8 @@ ERROR: <replaceable>reason</replaceable>
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by the <application>PostgreSQL</application> user (the user ID the
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server runs as), not the client.
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<command>COPY</command> naming a file is only allowed to database
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superusers, since it allows writing on any file that the backend has
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privileges to write on.
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superusers, since it allows reading or writing any file that the backend
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has privileges to access.
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<tip>
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<para>
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@ -297,57 +297,109 @@ ERROR: <replaceable>reason</replaceable>
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<title>File Formats</title>
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<refsect2>
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<refsect2info>
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<date>2001-01-02</date>
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<date>2002-02-12</date>
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</refsect2info>
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<title>Text Format</title>
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<para>
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When <command>COPY TO</command> is used without the BINARY option,
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the file generated will have each row (instance) on a single line, with each
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column (attribute) separated by the delimiter character. Embedded
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delimiter characters will be preceded by a backslash character
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("\"). The attribute values themselves are strings generated by the
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output function associated with each attribute type. The output
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function for a type should not try to generate the backslash
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character; this will be handled by <command>COPY</command> itself.
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When <command>COPY</command> is used without the BINARY option,
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the file read or written is a text file with one line per table row.
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Columns (attributes) in a row are separated by the delimiter character.
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The attribute values themselves are strings generated by the
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output function, or acceptable to the input function, of each
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attribute's data type. The specified null-value string is used in
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place of attributes that are NULL.
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</para>
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<para>
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If WITH OIDS is specified, the OID is read or written as the first column,
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preceding the user data columns. (An error is raised if WITH OIDS is
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specified for a table that does not have OIDs.)
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</para>
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<para>
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End of data can be represented by a single line containing just
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backslash-period (<literal>\.</>). An end-of-data marker is
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not necessary when reading from a Unix file, since the end of file
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serves perfectly well; but an end marker must be provided when copying
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data to or from a client application.
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</para>
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<para>
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Backslash characters (<literal>\</>) may be used in the
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<command>COPY</command> data to quote data characters that might otherwise
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be taken as row or column delimiters. In particular, the following
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characters <emphasis>must</> be preceded by a backslash if they appear
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as part of an attribute value: backslash itself, newline, and the current
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delimiter character.
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</para>
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<para>
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The following special backslash sequences are recognized by
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<command>COPY FROM</command>:
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Sequence</entry>
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<entry>Represents</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><literal>\b</></entry>
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<entry>Backspace (ASCII 8)</entry>
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</row>
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<row>
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<entry><literal>\f</></entry>
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<entry>Form feed (ASCII 12)</entry>
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</row>
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<row>
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<entry><literal>\n</></entry>
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<entry>Newline (ASCII 10)</entry>
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</row>
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<row>
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<entry><literal>\r</></entry>
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<entry>Carriage return (ASCII 13)</entry>
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</row>
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<row>
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<entry><literal>\t</></entry>
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<entry>Tab (ASCII 9)</entry>
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</row>
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<row>
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<entry><literal>\v</></entry>
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<entry>Vertical tab (ASCII 11)</entry>
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</row>
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<row>
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<entry><literal>\</><replaceable>digits</></entry>
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<entry>Backslash followed by one to three octal digits specifies
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the character with that numeric code</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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Presently, <command>COPY TO</command> will never emit an octal-digits
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backslash sequence, but it does use the other sequences listed above
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for those control characters.
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</para>
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<para>
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Never put a backslash before a data character <literal>N</> or period
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(<literal>.</>). Such pairs will be mistaken for the default null string
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or the end-of-data marker, respectively. Any other backslashed character
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that is not mentioned in the above table will be taken to represent itself.
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</para>
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<para>
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It is strongly recommended that applications generating COPY data convert
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data newlines and carriage returns to the <literal>\n</> and
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<literal>\r</> sequences respectively. At present
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(<productname>PostgreSQL</productname> 7.2 and older versions) it is
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possible to represent a data carriage return without any special quoting,
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and to represent a data newline by a backslash and newline. However,
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these representations will not be accepted by default in future releases.
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</para>
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<para>
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The actual format for each instance is
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<programlisting>
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<attr1><<replaceable class=parameter>separator</replaceable>><attr2><<replaceable class=parameter>separator</replaceable>>...<<replaceable class=parameter>separator</replaceable>><attr<replaceable class="parameter">n</replaceable>><newline>
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</programlisting>
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Note that the end of each row is marked by a Unix-style newline
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("\n"). <command>COPY FROM</command> will not behave as desired
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if given a file containing DOS- or Mac-style newlines.
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</para>
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<para>
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The OID is emitted as the first column if WITH OIDS is specified.
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(An error is raised if WITH OIDS is specified for a table that does not
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have OIDs.)
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</para>
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<para>
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If <command>COPY TO</command> is sending its output to standard
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output instead of a file, after the last row it will send a backslash ("\")
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and a period (".") followed by a newline.
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Similarly, if <command>COPY FROM</command> is reading
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from standard input, it will expect a backslash ("\") and a period
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(".") followed by a newline, as the first three characters on a
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line to denote end-of-file. However, <command>COPY FROM</command>
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will terminate correctly (followed by the backend itself) if the
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input connection is closed before this special end-of-file pattern is
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found.
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</para>
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<para>
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The backslash character has other special meanings. A literal backslash
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character is represented as two
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consecutive backslashes ("\\"). A literal tab character is represented
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as a backslash and a tab. (If you are using something other than tab
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as the column delimiter, backslash that delimiter character to include
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it in data.) A literal newline character is
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represented as a backslash and a newline. When loading text data
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not generated by <application>PostgreSQL</application>,
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you will need to convert backslash
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characters ("\") to double-backslashes ("\\") to ensure that they
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are loaded properly.
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("\n"). Presently, <command>COPY FROM</command> will not behave as
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desired if given a file containing DOS- or Mac-style newlines.
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This is expected to change in future releases.
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</para>
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</refsect2>
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@ -7,7 +7,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.144 2001/12/04 21:19:57 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.145 2002/02/12 21:25:41 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -41,7 +41,7 @@
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#endif
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#define ISOCTAL(c) (((c) >= '0') && ((c) <= '7'))
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#define VALUE(c) ((c) - '0')
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#define OCTVALUE(c) ((c) - '0')
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/* non-export function prototypes */
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@ -83,13 +83,13 @@ static int server_encoding;
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* Internal communications functions
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*/
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static void CopySendData(void *databuf, int datasize, FILE *fp);
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static void CopySendString(char *str, FILE *fp);
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static void CopySendString(const char *str, FILE *fp);
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static void CopySendChar(char c, FILE *fp);
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static void CopyGetData(void *databuf, int datasize, FILE *fp);
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static int CopyGetChar(FILE *fp);
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static int CopyGetEof(FILE *fp);
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static int CopyPeekChar(FILE *fp);
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static void CopyDonePeek(FILE *fp, int c, int pickup);
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static void CopyDonePeek(FILE *fp, int c, bool pickup);
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/*
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* CopySendData sends output data either to the file
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@ -118,9 +118,9 @@ CopySendData(void *databuf, int datasize, FILE *fp)
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}
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static void
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CopySendString(char *str, FILE *fp)
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CopySendString(const char *str, FILE *fp)
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{
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CopySendData(str, strlen(str), fp);
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CopySendData((void *) str, strlen(str), fp);
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}
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static void
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@ -178,10 +178,12 @@ CopyGetEof(FILE *fp)
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/*
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* CopyPeekChar reads a byte in "peekable" mode.
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*
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* after each call to CopyPeekChar, a call to CopyDonePeek _must_
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* follow, unless EOF was returned.
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* CopyDonePeek will either take the peeked char off the steam
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* (if pickup is != 0) or leave it on the stream (if pickup == 0)
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*
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* CopyDonePeek will either take the peeked char off the stream
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* (if pickup is true) or leave it on the stream (if pickup is false).
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*/
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static int
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CopyPeekChar(FILE *fp)
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@ -199,15 +201,13 @@ CopyPeekChar(FILE *fp)
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}
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static void
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CopyDonePeek(FILE *fp, int c, int pickup)
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CopyDonePeek(FILE *fp, int c, bool pickup)
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{
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if (!fp)
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{
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if (pickup)
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{
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/*
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* We want to pick it up
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*/
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/* We want to pick it up */
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(void) pq_getbyte();
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}
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/* If we didn't want to pick it up, just leave it where it sits */
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@ -219,7 +219,7 @@ CopyDonePeek(FILE *fp, int c, int pickup)
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/* We don't want to pick it up - so put it back in there */
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ungetc(c, fp);
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}
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/* If we wanted to pick it up, it's already there */
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/* If we wanted to pick it up, it's already done */
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}
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}
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@ -1078,31 +1078,30 @@ CopyReadAttribute(FILE *fp, bool *isnull, char *delim, int *newline, char *null_
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{
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int val;
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val = VALUE(c);
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val = OCTVALUE(c);
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c = CopyPeekChar(fp);
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if (ISOCTAL(c))
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{
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val = (val << 3) + VALUE(c);
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CopyDonePeek(fp, c, 1); /* Pick up the
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* character! */
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val = (val << 3) + OCTVALUE(c);
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CopyDonePeek(fp, c, true /*pick up*/);
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c = CopyPeekChar(fp);
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if (ISOCTAL(c))
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{
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CopyDonePeek(fp, c, 1); /* pick up! */
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val = (val << 3) + VALUE(c);
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val = (val << 3) + OCTVALUE(c);
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CopyDonePeek(fp, c, true /*pick up*/);
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}
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else
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{
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if (c == EOF)
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goto endOfFile;
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CopyDonePeek(fp, c, 0); /* Return to stream! */
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CopyDonePeek(fp, c, false /*put back*/);
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}
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}
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else
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{
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if (c == EOF)
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goto endOfFile;
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CopyDonePeek(fp, c, 0); /* Return to stream! */
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CopyDonePeek(fp, c, false /*put back*/);
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}
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c = val & 0377;
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}
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@ -1144,6 +1143,7 @@ CopyReadAttribute(FILE *fp, bool *isnull, char *delim, int *newline, char *null_
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}
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appendStringInfoCharMacro(&attribute_buf, c);
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#ifdef MULTIBYTE
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/* XXX shouldn't this be done even when encoding is the same? */
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if (client_encoding != server_encoding)
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{
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/* get additional bytes of the char, if any */
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@ -1190,15 +1190,18 @@ CopyAttributeOut(FILE *fp, char *server_string, char *delim)
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{
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char *string;
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char c;
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char delimc = delim[0];
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#ifdef MULTIBYTE
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bool same_encoding;
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char *string_start;
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int mblen;
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int i;
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#endif
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#ifdef MULTIBYTE
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if (client_encoding != server_encoding)
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same_encoding = (server_encoding == client_encoding);
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if (!same_encoding)
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{
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string = (char *) pg_server_to_client((unsigned char *) server_string,
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strlen(server_string));
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@ -1207,31 +1210,64 @@ CopyAttributeOut(FILE *fp, char *server_string, char *delim)
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else
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{
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string = server_string;
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string_start = NULL; /* unused, but keep compiler quiet */
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string_start = NULL;
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}
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#else
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string = server_string;
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#endif
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#ifdef MULTIBYTE
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for (; (mblen = (server_encoding == client_encoding ? 1 : pg_encoding_mblen(client_encoding, string))) &&
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((c = *string) != '\0'); string += mblen)
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for (; (c = *string) != '\0'; string += mblen)
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#else
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for (; (c = *string) != '\0'; string++)
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#endif
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{
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if (c == delim[0] || c == '\n' || c == '\\')
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CopySendChar('\\', fp);
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#ifdef MULTIBYTE
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for (i = 0; i < mblen; i++)
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CopySendChar(*(string + i), fp);
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#else
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CopySendChar(c, fp);
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mblen = 1;
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#endif
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switch (c)
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{
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case '\b':
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CopySendString("\\b", fp);
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break;
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case '\f':
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CopySendString("\\f", fp);
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break;
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case '\n':
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CopySendString("\\n", fp);
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break;
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case '\r':
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CopySendString("\\r", fp);
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break;
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case '\t':
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CopySendString("\\t", fp);
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break;
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case '\v':
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CopySendString("\\v", fp);
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break;
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case '\\':
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CopySendString("\\\\", fp);
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break;
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default:
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if (c == delimc)
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CopySendChar('\\', fp);
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CopySendChar(c, fp);
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#ifdef MULTIBYTE
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/* XXX shouldn't this be done even when encoding is same? */
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if (!same_encoding)
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{
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/* send additional bytes of the char, if any */
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mblen = pg_encoding_mblen(client_encoding, string);
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for (i = 1; i < mblen; i++)
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CopySendChar(string[i], fp);
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}
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#endif
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break;
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}
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}
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#ifdef MULTIBYTE
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if (client_encoding != server_encoding)
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if (string_start)
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pfree(string_start); /* pfree pg_server_to_client result */
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#endif
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}
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