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Update COPY BINARY file format spec to reflect recent decisions about

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external representation of binary data.
This commit is contained in:
Tom Lane 2003-05-07 22:23:27 +00:00
parent 2de6da832f
commit 1718f4c66c
1 changed files with 42 additions and 89 deletions
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131
doc/src/sgml/ref/copy.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.44 2003/04/20 01:52:55 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.45 2003/05/07 22:23:27 tgl Exp $
PostgreSQL documentation
-->
@ -119,7 +119,7 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
<term><literal>BINARY</literal></term>
<listitem>
<para>
Forces all data to be stored or read in binary format rather
Causes all data to be stored or read in binary format rather
than as text. You cannot specify the <option>DELIMITER</option>
or <option>NULL</option> options in binary mode.
</para>
@ -193,17 +193,18 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
</para>
<para>
The <literal>BINARY</literal> key word will force all data to be
The <literal>BINARY</literal> key word causes all data to be
stored/read as binary format rather than as text. It is
somewhat faster than the normal text mode, but a binary format
file is not portable across machine architectures.
somewhat faster than the normal text mode, but a binary-format
file is less portable across machine architectures and
<productname>PostgreSQL</productname> versions.
</para>
<para>
You must have select privilege on any table
You must have select privilege on the table
whose values are read by <command>COPY TO</command>, and
insert privilege on a table into which values
are being inserted by <command>COPY FROM</command>.
insert privilege on the table into which values
are inserted by <command>COPY FROM</command>.
</para>
<para>
@ -279,8 +280,8 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
End of data can be represented by a single line containing just
backslash-period (<literal>\.</>). An end-of-data marker is
not necessary when reading from a file, since the end of file
serves perfectly well; but an end marker must be provided when copying
data to or from a client application.
serves perfectly well; it is needed only when copying data to or from
client applications using pre-3.0 client protocol.
</para>
<para>
@ -358,6 +359,9 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
possible to represent a data carriage return by a backslash and carriage
return, and to represent a data newline by a backslash and newline.
However, these representations might not be accepted in future releases.
They are also highly vulnerable to corruption if the COPY file is
transferred across different machines (for example, from Unix to Windows
or vice versa).
</para>
<para>
@ -374,7 +378,7 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
<para>
The file format used for <command>COPY BINARY</command> changed in
<application>PostgreSQL</application> 7.1. The new format consists
<application>PostgreSQL</application> 7.4. The new format consists
of a file header, zero or more tuples containing the row data, and
a file trailer.
</para>
@ -383,7 +387,7 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
<title>File Header</title>
<para>
The file header consists of 24 bytes of fixed fields, followed
The file header consists of 15 bytes of fixed fields, followed
by a variable-length header extension area. The fixed fields are:
<variablelist>
@ -391,7 +395,7 @@ COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="
<term>Signature</term>
<listitem>
<para>
12-byte sequence <literal>PGBCOPY\n\377\r\n\0</> --- note that the zero byte
11-byte sequence <literal>PGCOPY\n\377\r\n\0</> --- note that the zero byte
is a required part of the signature. (The signature is designed to allow
easy identification of files that have been munged by a non-8-bit-clean
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.)
</listitem>
</varlistentry>
<varlistentry>
<term>Integer layout field</term>
<listitem>
<para>
32-bit integer constant 0x01020304 in source's byte order. Potentially, a reader
could engage in byte-flipping of subsequent fields if the wrong byte
order is detected here.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Flags field</term>
<listitem>
<para>
32-bit integer bit mask to denote important aspects of the file format. Bits are
numbered from 0 (<acronym>LSB</>) to 31 (<acronym>MSB</>) --- note that this field is stored
with source's endianness, as are all subsequent integer fields. Bits
32-bit integer bit mask to denote important aspects of the file format. Bits
are numbered from 0 (<acronym>LSB</>) to 31 (<acronym>MSB</>). Note that
this field is stored in network byte order (most significant byte first),
as are all the integer fields used in the file format. Bits
16-31 are reserved to denote critical file format issues; a reader
should abort if it finds an unexpected bit set in this range. Bits 0-15
are reserved to signal backwards-compatible format issues; a reader
@ -471,72 +465,28 @@ is left for a later release.
<title>Tuples</title>
<para>
Each tuple begins with a 16-bit integer count of the number of fields in the
tuple. (Presently, all tuples in a table will have the same count, but
that might not always be true.) Then, repeated for each field in the
tuple, there is a 16-bit integer <structfield>typlen</> word possibly followed by field data.
The <structfield>typlen</> field is interpreted thus:
<variablelist>
<varlistentry>
<term>Zero</term>
<listitem>
<para>
Field is null. No data follows.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>&gt; 0</term>
<listitem>
<para>
Field is a fixed-length data type. Exactly that many
bytes of data follow the <structfield>typlen</> word.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-1</term>
<listitem>
<para>
Field is a <literal>varlena</> data type. The next four
bytes are the <literal>varlena</> header, which contains
the total value length including the header itself.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>&lt; -1</term>
<listitem>
<para>
Reserved for future use.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
For nonnull fields, the reader can check that the <structfield>typlen</> matches the
expected <structfield>typlen</> for the destination column. This provides a simple
but very useful check that the data is as expected.
tuple. (Presently, all tuples in a table will have the same count, but that
might not always be true.) Then, repeated for each field in the tuple, there
is a 32-bit length word followed by that many bytes of field data. (The
length word does not include itself, and can be zero.) As a special case,
-1 indicates a NULL field value. No value bytes follow in the NULL case.
</para>
<para>
There is no alignment padding or any other extra data between fields.
Note also that the format does not distinguish whether a data type is
pass-by-reference or pass-by-value. Both of these provisions are
deliberate: they might help improve portability of the files (although
of course endianness and floating-point-format issues can still keep
you from moving a binary file across machines).
</para>
<para>
Presently, all data values in a <command>COPY BINARY</command> file are
assumed to be in binary format (format code one). It is anticipated that a
future extension may add a header field that allows per-column format codes
to be specified.
</para>
<para>
If OIDs are included in the file, the OID field immediately follows the
field-count word. It is a normal field except that it's not included
in the field-count. In particular it has a <structfield>typlen</> --- this will allow
in the field-count. In particular it has a length word --- this will allow
handling of 4-byte vs. 8-byte OIDs without too much pain, and will allow
OIDs to be shown as null if that ever proves desirable.
</para>
@ -546,8 +496,8 @@ OIDs to be shown as null if that ever proves desirable.
<title>File Trailer</title>
<para>
The file trailer consists of an 16-bit integer word containing -1. This is
easily distinguished from a tuple's field-count word.
The file trailer consists of a 16-bit integer word containing -1. This
is easily distinguished from a tuple's field-count word.
</para>
<para>
@ -579,19 +529,22 @@ COPY country FROM '/usr1/proj/bray/sql/country_data';
<para>
Here is a sample of data suitable for copying into a table from
<literal>STDIN</literal> (so it must have the termination sequence on the
last line):
<literal>STDIN</literal>:
<programlisting>
AF AFGHANISTAN
AL ALBANIA
DZ ALGERIA
ZM ZAMBIA
ZW ZIMBABWE
\.
</programlisting>
Note that the white space on each line is actually a tab character.
</para>
<para>
XXX the following example is OBSOLETE and needs to be updated for the
7.4 binary format:
</para>
<para>
The following is the same data, output in binary format on a
Linux/i586 machine. The data is shown after filtering through the