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Commit1718f4c

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Update COPY BINARY file format spec to reflect recent decisions about
external representation of binary data.
1 parent2de6da8 commit1718f4c

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1 file changed

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‎doc/src/sgml/ref/copy.sgml‎

Lines changed: 40 additions & 87 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.44 2003/04/20 01:52:55 momjian Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.45 2003/05/07 22:23:27 tgl Exp $
33
PostgreSQL documentation
44
-->
55

@@ -119,7 +119,7 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
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<term><literal>BINARY</literal></term>
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<listitem>
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<para>
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Forces all data to be stored or read in binary format rather
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Causes all data to be stored or read in binary format rather
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than as text. You cannot specify the <option>DELIMITER</option>
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or <option>NULL</option> options in binary mode.
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</para>
@@ -193,17 +193,18 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
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</para>
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<para>
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The <literal>BINARY</literal> key wordwill force all data to be
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The <literal>BINARY</literal> key wordcauses all data to be
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stored/read as binary format rather than as text. It is
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somewhat faster than the normal text mode, but a binary format
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file is not portable across machine architectures.
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somewhat faster than the normal text mode, but a binary-format
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file is less portable across machine architectures and
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<productname>PostgreSQL</productname> versions.
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</para>
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<para>
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You must have select privilege onany table
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You must have select privilege onthe table
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whose values are read by <command>COPY TO</command>, and
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insert privilege ona table into which values
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arebeinginserted by <command>COPY FROM</command>.
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insert privilege onthe table into which values
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are inserted by <command>COPY FROM</command>.
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</para>
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<para>
@@ -279,8 +280,8 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
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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 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 aclientapplication.
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serves perfectly well;it is needed only when copying data to or from
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client applications using pre-3.0clientprotocol.
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</para>
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<para>
@@ -358,6 +359,9 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
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possible to represent a data carriage return by a backslash and carriage
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return, and to represent a data newline by a backslash and newline.
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However, these representations might not be accepted in future releases.
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They are also highly vulnerable to corruption if the COPY file is
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transferred across different machines (for example, from Unix to Windows
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or vice versa).
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</para>
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<para>
@@ -374,7 +378,7 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
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<para>
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The file format used for <command>COPY BINARY</command> changed in
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<application>PostgreSQL</application> 7.1. The new format consists
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<application>PostgreSQL</application> 7.4. The new format consists
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of a file header, zero or more tuples containing the row data, and
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a file trailer.
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</para>
@@ -383,15 +387,15 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
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<title>File Header</title>
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<para>
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The file header consists of24 bytes of fixed fields, followed
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The file header consists of15 bytes of fixed fields, followed
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by a variable-length header extension area. The fixed fields are:
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<variablelist>
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<varlistentry>
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<term>Signature</term>
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<listitem>
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<para>
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12-byte sequence <literal>PGBCOPY\n\377\r\n\0</> --- note that the zero byte
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11-byte sequence <literal>PGCOPY\n\377\r\n\0</> --- note that the zero byte
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is a required part of the signature. (The signature is designed to allow
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easy identification of files that have been munged by a non-8-bit-clean
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transfer. This signature will be changed by end-of-line-translation
@@ -400,24 +404,14 @@ filters, dropped zero bytes, dropped high bits, or parity changes.)
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Integer layout field</term>
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<listitem>
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<para>
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32-bit integer constant 0x01020304 in source's byte order. Potentially, a reader
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could engage in byte-flipping of subsequent fields if the wrong byte
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order is detected here.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Flags field</term>
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<listitem>
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<para>
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32-bit integer bit mask to denote important aspects of the file format. Bits are
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numbered from 0 (<acronym>LSB</>) to 31 (<acronym>MSB</>) --- note that this field is stored
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with source's endianness, as are all subsequent integer fields. Bits
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32-bit integer bit mask to denote important aspects of the file format. Bits
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are numbered from 0 (<acronym>LSB</>) to 31 (<acronym>MSB</>). Note that
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this field is stored in network byte order (most significant byte first),
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as are all the integer fields used in the file format. Bits
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16-31 are reserved to denote critical file format issues; a reader
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should abort if it finds an unexpected bit set in this range. Bits 0-15
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are reserved to signal backwards-compatible format issues; a reader
@@ -471,72 +465,28 @@ is left for a later release.
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<title>Tuples</title>
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<para>
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Each tuple begins with a 16-bit integer count of the number of fields in the
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tuple. (Presently, all tuples in a table will have the same count, but
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that might not always be true.) Then, repeated for each field in the
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tuple, there is a 16-bit integer <structfield>typlen</> word possibly followed by field data.
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The <structfield>typlen</> field is interpreted thus:
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<variablelist>
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<varlistentry>
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<term>Zero</term>
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<listitem>
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<para>
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Field is null. No data follows.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>&gt; 0</term>
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<listitem>
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<para>
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Field is a fixed-length data type. Exactly that many
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bytes of data follow the <structfield>typlen</> word.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>-1</term>
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<listitem>
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<para>
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Field is a <literal>varlena</> data type. The next four
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bytes are the <literal>varlena</> header, which contains
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the total value length including the header itself.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>&lt; -1</term>
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<listitem>
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<para>
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Reserved for future use.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
468+
tuple. (Presently, all tuples in a table will have the same count, but that
469+
might not always be true.) Then, repeated for each field in the tuple, there
470+
is a 32-bit length word followed by that many bytes of field data. (The
471+
length word does not include itself, and can be zero.) As a special case,
472+
-1 indicates a NULL field value. No value bytes follow in the NULL case.
519473
</para>
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<para>
522-
For nonnull fields, the reader can check that the <structfield>typlen</> matches the
523-
expected <structfield>typlen</> for the destination column. This provides a simple
524-
but very useful check that the data is as expected.
476+
There is no alignment padding or any other extra data between fields.
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</para>
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527479
<para>
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There is no alignment padding or any other extra data between fields.
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Note also that the format does not distinguish whether a data type is
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pass-by-reference or pass-by-value. Both of these provisions are
531-
deliberate: they might help improve portability of the files (although
532-
of course endianness and floating-point-format issues can still keep
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you from moving a binary file across machines).
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Presently, all data values in a <command>COPY BINARY</command> file are
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assumed to be in binary format (format code one). It is anticipated that a
482+
future extension may add a header field that allows per-column format codes
483+
to be specified.
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</para>
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<para>
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If OIDs are included in the file, the OID field immediately follows the
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field-count word. It is a normal field except that it's not included
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in the field-count. In particular it has a<structfield>typlen</> --- this will allow
489+
in the field-count. In particular it has alength word --- this will allow
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handling of 4-byte vs. 8-byte OIDs without too much pain, and will allow
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OIDs to be shown as null if that ever proves desirable.
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</para>
@@ -546,8 +496,8 @@ OIDs to be shown as null if that ever proves desirable.
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<title>File Trailer</title>
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<para>
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The file trailer consists ofan 16-bit integer word containing -1. This is
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easily distinguished from a tuple's field-count word.
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The file trailer consists ofa 16-bit integer word containing -1. This
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iseasily distinguished from a tuple's field-count word.
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</para>
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<para>
@@ -579,19 +529,22 @@ COPY country FROM '/usr1/proj/bray/sql/country_data';
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<para>
581531
Here is a sample of data suitable for copying into a table from
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<literal>STDIN</literal> (so it must have the termination sequence on the
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last line):
532+
<literal>STDIN</literal>:
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<programlisting>
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AF AFGHANISTAN
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AL ALBANIA
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DZ ALGERIA
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ZM ZAMBIA
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ZW ZIMBABWE
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\.
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</programlisting>
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Note that the white space on each line is actually a tab character.
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</para>
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543+
<para>
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XXX the following example is OBSOLETE and needs to be updated for the
545+
7.4 binary format:
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</para>
547+
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<para>
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The following is the same data, output in binary format on a
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Linux/i586 machine. The data is shown after filtering through the

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