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Postgres FD Implementation
Commit 676cf18c authored by Tom Lane's avatar Tom Lane
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New file format for COPY BINARY, in accordance with pghackers discussions 

of early December 2000.  COPY BINARY is now TOAST-safe.
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doc/src/sgml/ref/copy.sgml
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.18 2000/10/05 19:48:17 momjian Exp $ $Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.19 2001/01/03 20:04:09 tgl Exp $
Postgres documentation Postgres documentation
--> -->
...@@ -49,6 +49,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ] ...@@ -49,6 +49,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
<para> <para>
Changes the behavior of field formatting, forcing all data to be Changes the behavior of field formatting, forcing all data to be
stored or read in binary format rather than as text. stored or read in binary format rather than as text.
The DELIMITERS and WITH NULL options are irrelevant for binary format.
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
...@@ -66,7 +67,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ] ...@@ -66,7 +67,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
<term>WITH OIDS</term> <term>WITH OIDS</term>
<listitem> <listitem>
<para> <para>
Copies the internal unique object id (OID) for each row. Specifies copying the internal unique object id (OID) for each row.
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
...@@ -84,7 +85,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ] ...@@ -84,7 +85,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
<term><filename>stdin</filename></term> <term><filename>stdin</filename></term>
<listitem> <listitem>
<para> <para>
Specifies that input comes from a pipe or terminal. Specifies that input comes from the client application.
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
...@@ -93,7 +94,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ] ...@@ -93,7 +94,7 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
<term><filename>stdout</filename></term> <term><filename>stdout</filename></term>
<listitem> <listitem>
<para> <para>
Specifies that output goes to a pipe or terminal. Specifies that output goes to the client application.
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
...@@ -102,16 +103,16 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ] ...@@ -102,16 +103,16 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
<term><replaceable class="parameter">delimiter</replaceable></term> <term><replaceable class="parameter">delimiter</replaceable></term>
<listitem> <listitem>
<para> <para>
A character that delimits the input or output fields. The character that separates fields within each row (line) of the file.
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
<varlistentry> <varlistentry>
<term><replaceable class="parameter">null print</replaceable></term> <term><replaceable class="parameter">null string</replaceable></term>
<listitem> <listitem>
<para> <para>
A string to represent NULL values. The default is The string that represents a NULL value. The default is
<quote><literal>\N</literal></quote> (backslash-N). <quote><literal>\N</literal></quote> (backslash-N).
You might prefer an empty string, for example. You might prefer an empty string, for example.
</para> </para>
...@@ -166,7 +167,7 @@ ERROR: <replaceable>reason</replaceable> ...@@ -166,7 +167,7 @@ ERROR: <replaceable>reason</replaceable>
<refsect1 id="R1-SQL-COPY-1"> <refsect1 id="R1-SQL-COPY-1">
<refsect1info> <refsect1info>
<date>1998-09-08</date> <date>2001-01-02</date>
</refsect1info> </refsect1info>
<title> <title>
Description Description
...@@ -176,17 +177,36 @@ ERROR: <replaceable>reason</replaceable> ...@@ -176,17 +177,36 @@ ERROR: <replaceable>reason</replaceable>
<productname>Postgres</productname> tables and <productname>Postgres</productname> tables and
standard file-system files. standard file-system files.
<command>COPY TO</command> copies the entire contents of a table to
a file, while <command>COPY FROM</command> copies data from a file to a
table (appending the data to whatever is in the table already).
</para>
<para>
<command>COPY</command> instructs <command>COPY</command> instructs
the <productname>Postgres</productname> backend the <productname>Postgres</productname> backend
to directly read from or write to a file. The file must be directly visible to to directly read from or write to a file. If a file name is specified,
the backend and the name must be specified from the viewpoint of the backend. the file must be accessible to the backend and the name must be specified
If <filename>stdin</filename> or <filename>stdout</filename> are from the viewpoint of the backend.
If <filename>stdin</filename> or <filename>stdout</filename> is
specified, data flows through the client frontend to the backend. specified, data flows through the client frontend to the backend.
</para>
<tip>
<para>
Do not confuse <command>COPY</command> with the
<application>psql</application> instruction <command>\copy</command>.
<command>\copy</command> invokes <command>COPY FROM stdin</command>
or <command>COPY TO stdout</command>, and then fetches/stores the data
in a file accessible to the <application>psql</application> client.
Thus, file accessibility and access rights depend on the client
rather than the backend when <command>\copy</command> is used.
</para>
</tip>
</para>
<refsect2 id="R2-SQL-COPY-3"> <refsect2 id="R2-SQL-COPY-3">
<refsect2info> <refsect2info>
<date>1998-09-08</date> <date>2001-01-02</date>
</refsect2info> </refsect2info>
<title> <title>
Notes Notes
...@@ -194,16 +214,19 @@ ERROR: <replaceable>reason</replaceable> ...@@ -194,16 +214,19 @@ ERROR: <replaceable>reason</replaceable>
<para> <para>
The BINARY keyword will force all data to be The BINARY keyword will force all data to be
stored/read as binary format rather than as text. It is stored/read as binary format rather than as text. It is
somewhat faster than the normal copy command, but is not somewhat faster than the normal copy command, but a binary copy
generally portable, and the files generated are somewhat larger, file is not portable across machine architectures.
although this factor is highly dependent on the data itself.
</para> </para>
<para> <para>
By default, a text copy uses a tab ("\t") character as a delimiter. By default, a text copy uses a tab ("\t") character as a delimiter
The delimiter may also be changed to any other single character between fields. The field delimiter may be changed to any other single
with the keyword phrase USING DELIMITERS. Characters character with the keyword phrase USING DELIMITERS. Characters
in data fields which happen to match the delimiter character will in data fields which happen to match the delimiter character will
be backslash quoted. be backslash quoted.
Note that the delimiter is always a single character.
If multiple characters are specified in the delimiter string,
only the first character is used.
</para> </para>
<para> <para>
...@@ -217,67 +240,63 @@ ERROR: <replaceable>reason</replaceable> ...@@ -217,67 +240,63 @@ ERROR: <replaceable>reason</replaceable>
</para> </para>
<para> <para>
The keyword phrase USING DELIMITERS specifies a single character <command>COPY TO</command> neither invokes rules nor acts on column
to be used for all delimiters between columns. If multiple characters defaults. It does invoke triggers and check constraints.
are specified in the delimiter string, only the first character is
used.
<tip>
<para>
Do not confuse <command>COPY</command> with the
<application>psql</application> instruction <command>\copy</command>.
</para>
</tip>
</para> </para>
<para>
<command>COPY</command> neither invokes rules nor acts on column defaults.
It does invoke triggers, however.
</para>
<para> <para>
<command>COPY</command> stops operation at the first error. This <command>COPY</command> stops operation at the first error. This
should not lead to problems in the event of should not lead to problems in the event of
a <command>COPY FROM</command>, but the a <command>COPY FROM</command>, but the
target relation will, of course, be partially modified in a target relation will already have received earlier rows in a
<command>COPY TO</command>. <command>COPY TO</command>. These rows will not be visible or
<command>VACUUM</command> should be used to clean up accessible, but they still occupy disk space. This may amount to a
after a failed copy. considerable amount
</para> of wasted disk space if the failure happened well into a large copy
<para> operation. You may wish to invoke <command>VACUUM</command> to recover
Because the Postgres backend's current working directory the wasted space.
is not usually the same as the user's
working directory, the result of copying to a file
"<filename>foo</filename>" (without
additional path information) may yield unexpected results for the
naive user. In this case, <filename>foo</filename>
will wind up in <filename>$PGDATA/foo</filename>. In
general, the full pathname as it would appear to the backend server machine
should be used when specifying files to
be copied.
</para> </para>
<para> <para>
Files used as arguments to <command>COPY</command> Files named in a <command>COPY</command> command are read or written
must reside on or be directly by the backend, not by the client application. Therefore,
accessible to the database server machine by being either on they must reside on or be accessible to the database server machine,
local disks or on a networked file system. not the client. They must be accessible to and readable or writable
by the Postgres user (the userid the backend runs as), not the client.
<command>COPY</command> naming a file is only allowed to database
superusers, since it allows writing on any file that the backend has
privileges to write on.
<tip>
<para>
The
<application>psql</application> instruction <command>\copy</command>
reads or writes files on the client machine with the client's
permissions, so it is not restricted to superusers.
</para>
</tip>
</para> </para>
<para> <para>
When a TCP/IP connection from one machine to another is used, and a It is recommended that the filename used in <command>COPY</command>
target file is specified, the target file will be written on the always be specified as an absolute path. This is enforced by the backend
machine where the backend is running rather than the user's in the case of <command>COPY TO</command>, but for <command>COPY
machine. FROM</command> you do have the option of reading from a file specified
by a relative path. The path will be interpreted relative to the
backend's working directory (somewhere below
<filename>$PGDATA</filename>), not the client's working directory.
</para> </para>
</refsect2> </refsect2>
</refsect1> </refsect1>
<refsect1 id="R1-SQL-COPY-2"> <refsect1 id="R1-SQL-COPY-2">
<refsect1info> <refsect1info>
<date>1998-05-04</date> <date>2001-01-02</date>
</refsect1info> </refsect1info>
<title>File Formats</title> <title>File Formats</title>
<refsect2> <refsect2>
<refsect2info> <refsect2info>
<date>1998-05-04</date> <date>2001-01-02</date>
</refsect2info> </refsect2info>
<title>Text Format</title> <title>Text Format</title>
<para> <para>
...@@ -293,27 +312,34 @@ ERROR: <replaceable>reason</replaceable> ...@@ -293,27 +312,34 @@ ERROR: <replaceable>reason</replaceable>
<para> <para>
The actual format for each instance is The actual format for each instance is
<programlisting> <programlisting>
&lt;attr1&gt;&lt;<replaceable class=parameter>separator</replaceable>&gt;&lt;attr2&gt;&lt;<replaceable class=parameter>separator</replaceable>&gt;...&lt;<replaceable class=parameter>separator</replaceable>&gt;&lt;attr<replaceable class="parameter">n</replaceable>&gt;&lt;newline&gt;. &lt;attr1&gt;&lt;<replaceable class=parameter>separator</replaceable>&gt;&lt;attr2&gt;&lt;<replaceable class=parameter>separator</replaceable>&gt;...&lt;<replaceable class=parameter>separator</replaceable>&gt;&lt;attr<replaceable class="parameter">n</replaceable>&gt;&lt;newline&gt;
</programlisting> </programlisting>
The oid is placed on the beginning of the line Note that the end of each row is marked by a Unix-style newline
if WITH OIDS is specified. ("\n"). <command>COPY FROM</command> will not behave as desired
if given a file containing DOS- or Mac-style newlines.
</para>
<para>
The OID is emitted as the first column if WITH OIDS is specified.
</para> </para>
<para> <para>
If <command>COPY</command> is sending its output to standard If <command>COPY TO</command> is sending its output to standard
output instead of a file, it will send a backslash("\") and a period output instead of a file, after the last row it will send a backslash ("\")
(".") followed immediately by a newline, on a separate line, and a period (".") followed by a newline.
when it is done. Similarly, if <command>COPY</command> is reading Similarly, if <command>COPY FROM</command> is reading
from standard input, it will expect a backslash ("\") and a period from standard input, it will expect a backslash ("\") and a period
(".") followed by a newline, as the first three characters on a (".") followed by a newline, as the first three characters on a
line to denote end-of-file. However, <command>COPY</command> line to denote end-of-file. However, <command>COPY FROM</command>
will terminate (followed by the backend itself) if a true EOF is will terminate correctly (followed by the backend itself) if the
encountered before this special end-of-file pattern is found. input connection is closed before this special end-of-file pattern is
found.
</para> </para>
<para> <para>
The backslash character has other special meanings. A literal backslash The backslash character has other special meanings. A literal backslash
character is represented as two character is represented as two
consecutive backslashes ("\\"). A literal tab character is represented consecutive backslashes ("\\"). A literal tab character is represented
as a backslash and a tab. A literal newline character is as a backslash and a tab. (If you are using something other than tab
as the column delimiter, backslash that delimiter character to include
it in data.) A literal newline character is
represented as a backslash and a newline. When loading text data represented as a backslash and a newline. When loading text data
not generated by <acronym>Postgres</acronym>, not generated by <acronym>Postgres</acronym>,
you will need to convert backslash you will need to convert backslash
...@@ -324,82 +350,207 @@ ERROR: <replaceable>reason</replaceable> ...@@ -324,82 +350,207 @@ ERROR: <replaceable>reason</replaceable>
<refsect2> <refsect2>
<refsect2info> <refsect2info>
<date>1998-05-04</date> <date>2001-01-02</date>
</refsect2info> </refsect2info>
<title>Binary Format</title> <title>Binary Format</title>
<para> <para>
In the case of <command>COPY BINARY</command>, the first four The file format used for <command>COPY BINARY</command> changed in
bytes in the file will be the number of instances in the file. If Postgres v7.1. The new format consists of a file header, zero or more
this number is zero, the <command>COPY BINARY</command> command tuples, and a file trailer.
will read until end-of-file is encountered. Otherwise, it will
stop reading when this number of instances has been read.
Remaining data in the file will be ignored.
</para>
<para>
The format for each instance in the file is as follows. Note that
this format must be followed <emphasis>exactly</emphasis>.
Unsigned four-byte integer quantities are called uint32 in the
table below.
</para>
<table frame="all">
<title>Contents of a binary copy file</title>
<tgroup cols="2" colsep="1" rowsep="1" align="center">
<colspec colname="col1">
<colspec colname="col2">
<spanspec namest="col1" nameend="col2" spanname="subhead">
<tbody>
<row>
<entry spanname="subhead" align="center">At the start of the file</entry>
</row>
<row>
<entry>uint32</entry>
<entry>number of tuples</entry>
</row>
<row>
<entry spanname="subhead" align="center">For each tuple</entry>
</row>
<row>
<entry>uint32</entry>
<entry>total length of tuple data</entry>
</row>
<row>
<entry>uint32</entry>
<entry>oid (if specified)</entry>
</row>
<row>
<entry>uint32</entry>
<entry>number of null attributes</entry>
</row>
<row>
<entry>[uint32,...,uint32]</entry>
<entry>attribute numbers of attributes, counting from 0</entry>
</row>
<row>
<entry>-</entry>
<entry>&lt;tuple data&gt;</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect2>
<refsect2>
<refsect2info>
<date>1998-05-04</date>
</refsect2info>
<title>Alignment of Binary Data</title>
<para>
On Sun-3s, 2-byte attributes are aligned on two-byte boundaries,
and all larger attributes are aligned on four-byte boundaries.
Character attributes are aligned on single-byte boundaries. On
most other machines, all attributes larger than 1 byte are aligned on
four-byte boundaries. Note that variable length attributes are
preceded by the attribute's length; arrays are simply contiguous
streams of the array element type.
</para> </para>
<refsect3>
<refsect3info>
<date>2001-01-02</date>
</refsect3info>
<title>
File Header
</title>
<para>
The file header consists of 24 bytes of fixed fields, followed
by a variable-length header extension area. The fixed fields are:
<variablelist>
<varlistentry>
<term>Signature</term>
<listitem>
<para>
12-byte sequence "PGBCOPY\n\377\r\n\0" --- note that the null
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 newline-translation
filters, dropped nulls, dropped high bits, or parity changes.)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Integer layout field</term>
<listitem>
<para>
int32 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>
int32 bit mask to denote important aspects of the file
format. Bits are numbered from 0 (LSB) to 31 (MSB) --- note that this
field is stored with source's endianness, as are all subsequent integer
fields. 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 should simply ignore any unexpected bits set in this range.
Currently only one flag bit is defined, and the rest must be zero:
<variablelist>
<varlistentry>
<term>Bit 16</term>
<listitem>
<para>
if 1, OIDs are included in the dump; if 0, not
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Header extension area length</term>
<listitem>
<para>
int32 length in bytes of remainder of header, not including self. In
the initial version this will be zero, and the first tuple follows
immediately. Future changes to the format might allow additional data
to be present in the header. A reader should silently skip over any header
extension data it does not know what to do with.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
The header extension area is envisioned to contain a sequence of
self-identifying chunks. The flags field is not intended to tell readers
what is in the extension area. Specific design of header extension contents
is left for a later release.
</para>
<para>
This design allows for both backwards-compatible header additions (add
header extension chunks, or set low-order flag bits) and
non-backwards-compatible changes (set high-order flag bits to signal such
changes, and add supporting data to the extension area if needed).
</para>
</refsect3>
<refsect3>
<refsect3info>
<date>2001-01-02</date>
</refsect3info>
<title>
Tuples
</title>
<para>
Each tuple begins with an int16 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 an int16 typlen word possibly followed by field data.
The 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 datatype. Exactly N
bytes of data follow the typlen word.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-1</term>
<listitem>
<para>
Field is a varlena datatype. The next four
bytes are the varlena header, which contains
the total value length including itself.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>&lt; -1</term>
<listitem>
<para>
Reserved for future use.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
For non-NULL fields, the reader can check that the typlen matches the
expected typlen for the destination column. This provides a simple
but very useful check that the data is as expected.
</para>
<para>
There is no alignment padding or any other extra data between fields.
Note also that the format does not distinguish whether a datatype 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>
If OIDs are included in the dump, 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 typlen --- 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 we someday allow OIDs to be optional.
</para>
</refsect3>
<refsect3>
<refsect3info>
<date>2001-01-02</date>
</refsect3info>
<title>
File Trailer
</title>
<para>
The file trailer consists of an int16 word containing -1. This is
easily distinguished from a tuple's field-count word.
</para>
<para>
A reader should report an error if a field-count word is neither -1
nor the expected number of columns. This provides an extra
check against somehow getting out of sync with the data.
</para>
</refsect3>
</refsect2> </refsect2>
</refsect1> </refsect1>
<refsect1 id="R1-SQL-COPY-3"> <refsect1 id="R1-SQL-COPY-3">
<title> <title>
...@@ -407,7 +558,7 @@ ERROR: <replaceable>reason</replaceable> ...@@ -407,7 +558,7 @@ ERROR: <replaceable>reason</replaceable>
</title> </title>
<para> <para>
The following example copies a table to standard output, The following example copies a table to standard output,
using a pipe (|) as the field using a vertical bar (|) as the field
delimiter: delimiter:
</para> </para>
<programlisting> <programlisting>
...@@ -425,36 +576,36 @@ COPY country FROM '/usr1/proj/bray/sql/country_data'; ...@@ -425,36 +576,36 @@ COPY country FROM '/usr1/proj/bray/sql/country_data';
has the termination sequence on the last line): has the termination sequence on the last line):
</para> </para>
<programlisting> <programlisting>
AF AFGHANISTAN AF AFGHANISTAN
AL ALBANIA AL ALBANIA
DZ ALGERIA DZ ALGERIA
... ZM ZAMBIA
ZM ZAMBIA ZW ZIMBABWE
ZW ZIMBABWE \.
\.
</programlisting> </programlisting>
<para> <para>
The following is the same data, output in binary format on a Linux/i586 machine. Note that the white space on each line is actually a TAB.
The data is shown after filtering through </para>
the Unix utility <command>od -c</command>. The table has <para>
three fields; the first is <classname>char(2)</classname> The following is the same data, output in binary format on a Linux/i586
and the second is <classname>text</classname>. All the machine. The data is shown after filtering through
the Unix utility <command>od -c</command>. The table has
three fields; the first is <classname>char(2)</classname>,
the second is <classname>text</classname>, and the third is
<classname>int4</classname>. All the
rows have a null value in the third field. rows have a null value in the third field.
Notice how the <classname>char(2)</classname>
field is padded with nulls to four bytes and the text field is
preceded by its length:
</para> </para>
<programlisting> <programlisting>
355 \0 \0 \0 027 \0 \0 \0 001 \0 \0 \0 002 \0 \0 \0 0000000 P G B C O P Y \n 377 \r \n \0 004 003 002 001
006 \0 \0 \0 A F \0 \0 017 \0 \0 \0 A F G H 0000020 \0 \0 \0 \0 \0 \0 \0 \0 003 \0 377 377 006 \0 \0 \0
A N I S T A N 023 \0 \0 \0 001 \0 \0 \0 002 0000040 A F 377 377 017 \0 \0 \0 A F G H A N I S
\0 \0 \0 006 \0 \0 \0 A L \0 \0 \v \0 \0 \0 A 0000060 T A N \0 \0 003 \0 377 377 006 \0 \0 \0 A L 377
L B A N I A 023 \0 \0 \0 001 \0 \0 \0 002 \0 0000100 377 \v \0 \0 \0 A L B A N I A \0 \0 003 \0
\0 \0 006 \0 \0 \0 D Z \0 \0 \v \0 \0 \0 A L 0000120 377 377 006 \0 \0 \0 D Z 377 377 \v \0 \0 \0 A L
G E R I A 0000140 G E R I A \0 \0 003 \0 377 377 006 \0 \0 \0 Z
... \n \0 \0 \0 Z A M B I A 024 \0 0000160 M 377 377 \n \0 \0 \0 Z A M B I A \0 \0 003
\0 \0 001 \0 \0 \0 002 \0 \0 \0 006 \0 \0 \0 Z W 0000200 \0 377 377 006 \0 \0 \0 Z W 377 377 \f \0 \0 \0 Z
\0 \0 \f \0 \0 \0 Z I M B A B W E 0000220 I M B A B W E \0 \0 377 377
</programlisting> </programlisting>
</refsect1> </refsect1>
......
src/backend/commands/copy.c
View file @ 676cf18c
...@@ -7,7 +7,7 @@ ...@@ -7,7 +7,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.126 2000/12/27 23:59:14 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.127 2001/01/03 20:04:10 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
...@@ -52,7 +52,8 @@ static Oid GetTypeElement(Oid type); ...@@ -52,7 +52,8 @@ static Oid GetTypeElement(Oid type);
static void CopyReadNewline(FILE *fp, int *newline); static void CopyReadNewline(FILE *fp, int *newline);
static char *CopyReadAttribute(FILE *fp, bool *isnull, char *delim, int *newline, char *null_print); static char *CopyReadAttribute(FILE *fp, bool *isnull, char *delim, int *newline, char *null_print);
static void CopyAttributeOut(FILE *fp, char *string, char *delim); static void CopyAttributeOut(FILE *fp, char *string, char *delim);
static int CountTuples(Relation relation);
static const char BinarySignature[12] = "PGBCOPY\n\377\r\n\0";
/* /*
* Static communication variables ... pretty grotty, but COPY has * Static communication variables ... pretty grotty, but COPY has
...@@ -387,7 +388,8 @@ DoCopy(char *relname, bool binary, bool oids, bool from, bool pipe, ...@@ -387,7 +388,8 @@ DoCopy(char *relname, bool binary, bool oids, bool from, bool pipe,
* Copy from relation TO file. * Copy from relation TO file.
*/ */
static void static void
CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_print) CopyTo(Relation rel, bool binary, bool oids, FILE *fp,
char *delim, char *null_print)
{ {
HeapTuple tuple; HeapTuple tuple;
TupleDesc tupDesc; TupleDesc tupDesc;
...@@ -398,20 +400,9 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p ...@@ -398,20 +400,9 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
FmgrInfo *out_functions; FmgrInfo *out_functions;
Oid *elements; Oid *elements;
bool *isvarlena; bool *isvarlena;
int32 *typmod; int16 fld_size;
char *nulls;
/*
* <nulls> is a (dynamically allocated) array with one character per
* attribute in the instance being copied. nulls[I-1] is 'n' if
* Attribute Number I is null, and ' ' otherwise.
*
* <nulls> is meaningful only if we are doing a binary copy.
*/
char *string; char *string;
scandesc = heap_beginscan(rel, 0, QuerySnapshot, 0, NULL);
tupDesc = rel->rd_att; tupDesc = rel->rd_att;
attr_count = rel->rd_att->natts; attr_count = rel->rd_att->natts;
attr = rel->rd_att->attrs; attr = rel->rd_att->attrs;
...@@ -420,7 +411,6 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p ...@@ -420,7 +411,6 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
out_functions = (FmgrInfo *) palloc(attr_count * sizeof(FmgrInfo)); out_functions = (FmgrInfo *) palloc(attr_count * sizeof(FmgrInfo));
elements = (Oid *) palloc(attr_count * sizeof(Oid)); elements = (Oid *) palloc(attr_count * sizeof(Oid));
isvarlena = (bool *) palloc(attr_count * sizeof(bool)); isvarlena = (bool *) palloc(attr_count * sizeof(bool));
typmod = (int32 *) palloc(attr_count * sizeof(int32));
for (i = 0; i < attr_count; i++) for (i = 0; i < attr_count; i++)
{ {
Oid out_func_oid; Oid out_func_oid;
...@@ -430,40 +420,62 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p ...@@ -430,40 +420,62 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
elog(ERROR, "COPY: couldn't lookup info for type %u", elog(ERROR, "COPY: couldn't lookup info for type %u",
attr[i]->atttypid); attr[i]->atttypid);
fmgr_info(out_func_oid, &out_functions[i]); fmgr_info(out_func_oid, &out_functions[i]);
typmod[i] = attr[i]->atttypmod;
} }
if (!binary) if (binary)
{ {
nulls = NULL; /* meaningless, but compiler doesn't know /* Generate header for a binary copy */
* that */ int32 tmp;
/* Signature */
CopySendData((char *) BinarySignature, 12, fp);
/* Integer layout field */
tmp = 0x01020304;
CopySendData(&tmp, sizeof(int32), fp);
/* Flags field */
tmp = 0;
if (oids)
tmp |= (1 << 16);
CopySendData(&tmp, sizeof(int32), fp);
/* No header extension */
tmp = 0;
CopySendData(&tmp, sizeof(int32), fp);
} }
else
{
int32 ntuples;
nulls = (char *) palloc(attr_count); scandesc = heap_beginscan(rel, 0, QuerySnapshot, 0, NULL);
for (i = 0; i < attr_count; i++)
nulls[i] = ' ';
/* XXX expensive */
ntuples = CountTuples(rel);
CopySendData(&ntuples, sizeof(int32), fp);
}
while (HeapTupleIsValid(tuple = heap_getnext(scandesc, 0))) while (HeapTupleIsValid(tuple = heap_getnext(scandesc, 0)))
{ {
bool need_delim = false;
if (QueryCancel) if (QueryCancel)
CancelQuery(); CancelQuery();
if (oids && !binary) if (binary)
{
/* Binary per-tuple header */
int16 fld_count = attr_count;
CopySendData(&fld_count, sizeof(int16), fp);
/* Send OID if wanted --- note fld_count doesn't include it */
if (oids)
{
fld_size = sizeof(Oid);
CopySendData(&fld_size, sizeof(int16), fp);
CopySendData(&tuple->t_data->t_oid, sizeof(Oid), fp);
}
}
else
{ {
string = DatumGetCString(DirectFunctionCall1(oidout, /* Text format has no per-tuple header, but send OID if wanted */
ObjectIdGetDatum(tuple->t_data->t_oid))); if (oids)
CopySendString(string, fp); {
CopySendChar(delim[0], fp); string = DatumGetCString(DirectFunctionCall1(oidout,
pfree(string); ObjectIdGetDatum(tuple->t_data->t_oid)));
CopySendString(string, fp);
pfree(string);
need_delim = true;
}
} }
for (i = 0; i < attr_count; i++) for (i = 0; i < attr_count; i++)
...@@ -474,18 +486,31 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p ...@@ -474,18 +486,31 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
origvalue = heap_getattr(tuple, i + 1, tupDesc, &isnull); origvalue = heap_getattr(tuple, i + 1, tupDesc, &isnull);
if (!binary)
{
if (need_delim)
CopySendChar(delim[0], fp);
need_delim = true;
}
if (isnull) if (isnull)
{ {
if (!binary) if (!binary)
{
CopySendString(null_print, fp); /* null indicator */ CopySendString(null_print, fp); /* null indicator */
}
else else
nulls[i] = 'n'; {
fld_size = 0; /* null marker */
CopySendData(&fld_size, sizeof(int16), fp);
}
} }
else else
{ {
/* /*
* If we have a toasted datum, forcibly detoast it to avoid * If we have a toasted datum, forcibly detoast it to avoid
* memory leakage inside the type's output routine. * memory leakage inside the type's output routine (or
* for binary case, becase we must output untoasted value).
*/ */
if (isvarlena[i]) if (isvarlena[i])
value = PointerGetDatum(PG_DETOAST_DATUM(origvalue)); value = PointerGetDatum(PG_DETOAST_DATUM(origvalue));
...@@ -495,75 +520,71 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p ...@@ -495,75 +520,71 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
if (!binary) if (!binary)
{ {
string = DatumGetCString(FunctionCall3(&out_functions[i], string = DatumGetCString(FunctionCall3(&out_functions[i],
value, value,
ObjectIdGetDatum(elements[i]), ObjectIdGetDatum(elements[i]),
Int32GetDatum(typmod[i]))); Int32GetDatum(attr[i]->atttypmod)));
CopyAttributeOut(fp, string, delim); CopyAttributeOut(fp, string, delim);
pfree(string); pfree(string);
} }
else
{
fld_size = attr[i]->attlen;
CopySendData(&fld_size, sizeof(int16), fp);
if (isvarlena[i])
{
/* varlena */
Assert(fld_size == -1);
CopySendData(DatumGetPointer(value),
VARSIZE(value),
fp);
}
else if (!attr[i]->attbyval)
{
/* fixed-length pass-by-reference */
Assert(fld_size > 0);
CopySendData(DatumGetPointer(value),
fld_size,
fp);
}
else
{
/* pass-by-value */
Datum datumBuf;
/*
* We need this horsing around because we don't know
* how shorter data values are aligned within a Datum.
*/
store_att_byval(&datumBuf, value, fld_size);
CopySendData(&datumBuf,
fld_size,
fp);
}
}
/* Clean up detoasted copy, if any */ /* Clean up detoasted copy, if any */
if (value != origvalue) if (value != origvalue)
pfree(DatumGetPointer(value)); pfree(DatumGetPointer(value));
} }
if (!binary)
{
if (i == attr_count - 1)
CopySendChar('\n', fp);
else
{
/*
* when copying out, only use the first char of the
* delim string
*/
CopySendChar(delim[0], fp);
}
}
} }
if (binary) if (!binary)
{ CopySendChar('\n', fp);
int32 null_ct = 0, }
length;
for (i = 0; i < attr_count; i++) heap_endscan(scandesc);
{
if (nulls[i] == 'n')
null_ct++;
}
length = tuple->t_len - tuple->t_data->t_hoff; if (binary)
CopySendData(&length, sizeof(int32), fp); {
if (oids) /* Generate trailer for a binary copy */
CopySendData((char *) &tuple->t_data->t_oid, sizeof(int32), fp); int16 fld_count = -1;
CopySendData(&null_ct, sizeof(int32), fp); CopySendData(&fld_count, sizeof(int16), fp);
if (null_ct > 0)
{
for (i = 0; i < attr_count; i++)
{
if (nulls[i] == 'n')
{
CopySendData(&i, sizeof(int32), fp);
nulls[i] = ' ';
}
}
}
CopySendData((char *) tuple->t_data + tuple->t_data->t_hoff,
length, fp);
}
} }
heap_endscan(scandesc);
pfree(out_functions); pfree(out_functions);
pfree(elements); pfree(elements);
pfree(isvarlena); pfree(isvarlena);
pfree(typmod);
if (binary)
pfree(nulls);
} }
...@@ -580,27 +601,20 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, ...@@ -580,27 +601,20 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp,
AttrNumber attr_count; AttrNumber attr_count;
FmgrInfo *in_functions; FmgrInfo *in_functions;
Oid *elements; Oid *elements;
int32 *typmod;
int i; int i;
Oid in_func_oid; Oid in_func_oid;
Datum *values; Datum *values;
char *nulls; char *nulls;
bool isnull; bool isnull;
int done = 0; int done = 0;
char *string = NULL, char *string;
*ptr;
int32 len,
null_ct,
null_id;
int32 ntuples,
tuples_read = 0;
bool reading_to_eof = true;
ResultRelInfo *resultRelInfo; ResultRelInfo *resultRelInfo;
EState *estate = CreateExecutorState(); /* for ExecConstraints() */ EState *estate = CreateExecutorState(); /* for ExecConstraints() */
TupleTable tupleTable; TupleTable tupleTable;
TupleTableSlot *slot; TupleTableSlot *slot;
Oid loaded_oid = InvalidOid; Oid loaded_oid = InvalidOid;
bool skip_tuple = false; bool skip_tuple = false;
bool file_has_oids;
tupDesc = RelationGetDescr(rel); tupDesc = RelationGetDescr(rel);
attr = tupDesc->attrs; attr = tupDesc->attrs;
...@@ -630,31 +644,58 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, ...@@ -630,31 +644,58 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp,
{ {
in_functions = (FmgrInfo *) palloc(attr_count * sizeof(FmgrInfo)); in_functions = (FmgrInfo *) palloc(attr_count * sizeof(FmgrInfo));
elements = (Oid *) palloc(attr_count * sizeof(Oid)); elements = (Oid *) palloc(attr_count * sizeof(Oid));
typmod = (int32 *) palloc(attr_count * sizeof(int32));
for (i = 0; i < attr_count; i++) for (i = 0; i < attr_count; i++)
{ {
in_func_oid = (Oid) GetInputFunction(attr[i]->atttypid); in_func_oid = (Oid) GetInputFunction(attr[i]->atttypid);
fmgr_info(in_func_oid, &in_functions[i]); fmgr_info(in_func_oid, &in_functions[i]);
elements[i] = GetTypeElement(attr[i]->atttypid); elements[i] = GetTypeElement(attr[i]->atttypid);
typmod[i] = attr[i]->atttypmod;
} }
file_has_oids = oids; /* must rely on user to tell us this... */
} }
else else
{ {
/* Read and verify binary header */
char readSig[12];
int32 tmp;
/* Signature */
CopyGetData(readSig, 12, fp);
if (CopyGetEof(fp) ||
memcmp(readSig, BinarySignature, 12) != 0)
elog(ERROR, "COPY BINARY: file signature not recognized");
/* Integer layout field */
CopyGetData(&tmp, sizeof(int32), fp);
if (CopyGetEof(fp) ||
tmp != 0x01020304)
elog(ERROR, "COPY BINARY: incompatible integer layout");
/* Flags field */
CopyGetData(&tmp, sizeof(int32), fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: bogus file header (missing flags)");
file_has_oids = (tmp & (1 << 16)) != 0;
tmp &= ~ (1 << 16);
if ((tmp >> 16) != 0)
elog(ERROR, "COPY BINARY: unrecognized critical flags in header");
/* Header extension length */
CopyGetData(&tmp, sizeof(int32), fp);
if (CopyGetEof(fp) ||
tmp < 0)
elog(ERROR, "COPY BINARY: bogus file header (missing length)");
/* Skip extension header, if present */
while (tmp-- > 0)
{
CopyGetData(readSig, 1, fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: bogus file header (wrong length)");
}
in_functions = NULL; in_functions = NULL;
elements = NULL; elements = NULL;
typmod = NULL;
CopyGetData(&ntuples, sizeof(int32), fp);
if (ntuples != 0)
reading_to_eof = false;
} }
values = (Datum *) palloc(attr_count * sizeof(Datum)); values = (Datum *) palloc(attr_count * sizeof(Datum));
nulls = (char *) palloc(attr_count * sizeof(char)); nulls = (char *) palloc(attr_count * sizeof(char));
for (i = 0; i < attr_count; i++)
nulls[i] = ' ';
lineno = 0; lineno = 0;
fe_eof = false; fe_eof = false;
...@@ -668,15 +709,22 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, ...@@ -668,15 +709,22 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp,
lineno++; lineno++;
/* Initialize all values for row to NULL */
MemSet(values, 0, attr_count * sizeof(Datum));
MemSet(nulls, 'n', attr_count * sizeof(char));
if (!binary) if (!binary)
{ {
int newline = 0; int newline = 0;
if (oids) if (file_has_oids)
{ {
string = CopyReadAttribute(fp, &isnull, delim, &newline, null_print); string = CopyReadAttribute(fp, &isnull, delim,
if (string == NULL) &newline, null_print);
done = 1; if (isnull)
elog(ERROR, "COPY TEXT: NULL Oid");
else if (string == NULL)
done = 1; /* end of file */
else else
{ {
loaded_oid = DatumGetObjectId(DirectFunctionCall1(oidin, loaded_oid = DatumGetObjectId(DirectFunctionCall1(oidin,
...@@ -685,22 +733,24 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, ...@@ -685,22 +733,24 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp,
elog(ERROR, "COPY TEXT: Invalid Oid"); elog(ERROR, "COPY TEXT: Invalid Oid");
} }
} }
for (i = 0; i < attr_count && !done; i++) for (i = 0; i < attr_count && !done; i++)
{ {
string = CopyReadAttribute(fp, &isnull, delim, &newline, null_print); string = CopyReadAttribute(fp, &isnull, delim,
&newline, null_print);
if (isnull) if (isnull)
{ {
values[i] = PointerGetDatum(NULL); /* already set values[i] and nulls[i] */
nulls[i] = 'n';
} }
else if (string == NULL) else if (string == NULL)
done = 1; done = 1; /* end of file */
else else
{ {
values[i] = FunctionCall3(&in_functions[i], values[i] = FunctionCall3(&in_functions[i],
CStringGetDatum(string), CStringGetDatum(string),
ObjectIdGetDatum(elements[i]), ObjectIdGetDatum(elements[i]),
Int32GetDatum(typmod[i])); Int32GetDatum(attr[i]->atttypmod));
nulls[i] = ' ';
} }
} }
if (!done) if (!done)
...@@ -708,47 +758,103 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, ...@@ -708,47 +758,103 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp,
} }
else else
{ /* binary */ { /* binary */
CopyGetData(&len, sizeof(int32), fp); int16 fld_count,
if (CopyGetEof(fp)) fld_size;
CopyGetData(&fld_count, sizeof(int16), fp);
if (CopyGetEof(fp) ||
fld_count == -1)
done = 1; done = 1;
else else
{ {
if (oids) if (fld_count <= 0 || fld_count > attr_count)
elog(ERROR, "COPY BINARY: tuple field count is %d, expected %d",
(int) fld_count, attr_count);
if (file_has_oids)
{ {
CopyGetData(&loaded_oid, sizeof(int32), fp); CopyGetData(&fld_size, sizeof(int16), fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: unexpected EOF");
if (fld_size != (int16) sizeof(Oid))
elog(ERROR, "COPY BINARY: sizeof(Oid) is %d, expected %d",
(int) fld_size, (int) sizeof(Oid));
CopyGetData(&loaded_oid, sizeof(Oid), fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: unexpected EOF");
if (loaded_oid == InvalidOid) if (loaded_oid == InvalidOid)
elog(ERROR, "COPY BINARY: Invalid Oid"); elog(ERROR, "COPY BINARY: Invalid Oid");
} }
CopyGetData(&null_ct, sizeof(int32), fp);
if (null_ct > 0) for (i = 0; i < (int) fld_count; i++)
{ {
for (i = 0; i < null_ct; i++) CopyGetData(&fld_size, sizeof(int16), fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: unexpected EOF");
if (fld_size == 0)
continue; /* it's NULL; nulls[i] already set */
if (fld_size != attr[i]->attlen)
elog(ERROR, "COPY BINARY: sizeof(field %d) is %d, expected %d",
i+1, (int) fld_size, (int) attr[i]->attlen);
if (fld_size == -1)
{ {
CopyGetData(&null_id, sizeof(int32), fp); /* varlena field */
nulls[null_id] = 'n'; int32 varlena_size;
Pointer varlena_ptr;
CopyGetData(&varlena_size, sizeof(int32), fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: unexpected EOF");
if (varlena_size < (int32) sizeof(int32))
elog(ERROR, "COPY BINARY: bogus varlena length");
varlena_ptr = (Pointer) palloc(varlena_size);
VARATT_SIZEP(varlena_ptr) = varlena_size;
CopyGetData(VARDATA(varlena_ptr),
varlena_size - sizeof(int32),
fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: unexpected EOF");
values[i] = PointerGetDatum(varlena_ptr);
}
else if (!attr[i]->attbyval)
{
/* fixed-length pass-by-reference */
Pointer refval_ptr;
Assert(fld_size > 0);
refval_ptr = (Pointer) palloc(fld_size);
CopyGetData(refval_ptr, fld_size, fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: unexpected EOF");
values[i] = PointerGetDatum(refval_ptr);
}
else
{
/* pass-by-value */
Datum datumBuf;
/*
* We need this horsing around because we don't know
* how shorter data values are aligned within a Datum.
*/
Assert(fld_size > 0 && fld_size <= sizeof(Datum));
CopyGetData(&datumBuf, fld_size, fp);
if (CopyGetEof(fp))
elog(ERROR, "COPY BINARY: unexpected EOF");
values[i] = fetch_att(&datumBuf, true, fld_size);
} }
}
string = (char *) palloc(len);
CopyGetData(string, len, fp);
ptr = string;
for (i = 0; i < attr_count; i++) nulls[i] = ' ';
{
if (nulls[i] == 'n')
continue;
ptr = (char *) att_align((long) ptr, attr[i]->attlen, attr[i]->attalign);
values[i] = fetchatt(attr[i], ptr);
ptr = att_addlength(ptr, attr[i]->attlen, ptr);
} }
} }
} }
if (done) if (done)
continue; break;
tuple = heap_formtuple(tupDesc, values, nulls); tuple = heap_formtuple(tupDesc, values, nulls);
if (oids)
if (oids && file_has_oids)
tuple->t_data->t_oid = loaded_oid; tuple->t_data->t_oid = loaded_oid;
skip_tuple = false; skip_tuple = false;
...@@ -796,25 +902,13 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, ...@@ -796,25 +902,13 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp,
ExecARInsertTriggers(rel, tuple); ExecARInsertTriggers(rel, tuple);
} }
if (binary)
pfree(string);
for (i = 0; i < attr_count; i++) for (i = 0; i < attr_count; i++)
{ {
if (!attr[i]->attbyval && nulls[i] != 'n') if (!attr[i]->attbyval && nulls[i] != 'n')
{ pfree(DatumGetPointer(values[i]));
if (!binary)
pfree((void *) values[i]);
}
/* reset nulls[] array for next time */
nulls[i] = ' ';
} }
heap_freetuple(tuple); heap_freetuple(tuple);
tuples_read++;
if (!reading_to_eof && ntuples == tuples_read)
done = true;
} }
/* /*
...@@ -829,7 +923,6 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, ...@@ -829,7 +923,6 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp,
{ {
pfree(in_functions); pfree(in_functions);
pfree(elements); pfree(elements);
pfree(typmod);
} }
ExecDropTupleTable(tupleTable, true); ExecDropTupleTable(tupleTable, true);
...@@ -1099,26 +1192,3 @@ CopyAttributeOut(FILE *fp, char *server_string, char *delim) ...@@ -1099,26 +1192,3 @@ CopyAttributeOut(FILE *fp, char *server_string, char *delim)
pfree(string_start); /* pfree pg_server_to_client result */ pfree(string_start); /* pfree pg_server_to_client result */
#endif #endif
} }
/*
* Returns the number of tuples in a relation. Unfortunately, currently
* must do a scan of the entire relation to determine this.
*
* relation is expected to be an open relation descriptor.
*/
static int
CountTuples(Relation relation)
{
HeapScanDesc scandesc;
HeapTuple tuple;
int i;
scandesc = heap_beginscan(relation, 0, QuerySnapshot, 0, NULL);
i = 0;
while (HeapTupleIsValid(tuple = heap_getnext(scandesc, 0)))
i++;
heap_endscan(scandesc);
return i;
}
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