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ALTER TABLE DROP COLUMN works. Patch by Christopher Kings-Lynne,

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code review by Tom Lane.  Remaining issues: functions that take or
return tuple types are likely to break if one drops (or adds!)
a column in the table defining the type.  Need to think about what
to do here.

Along the way: some code review for recent COPY changes; mark system
columns attnotnull = true where appropriate, per discussion a month ago.
This commit is contained in:
Tom Lane
2002-08-02 18:15:10 +00:00
parent 5e6528adf7
commit 38bb77a5d1
44 changed files with 1823 additions and 891 deletions
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13
doc/src/sgml/catalogs.sgml
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@ -1,6 +1,6 @@
<!--
Documentation of the system catalogs, directed toward PostgreSQL developers
$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.50 2002/07/31 17:19:49 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.51 2002/08/02 18:15:04 tgl Exp $
-->
<chapter id="catalogs">
@ -810,6 +810,17 @@
</entry>
</row>
<row>
<entry>attisdropped</entry>
<entry><type>bool</type></entry>
<entry></entry>
<entry>
This column has been dropped and is no longer valid. A dropped
column is still physically present in the table, but is
ignored by the parser and so cannot be accessed via SQL.
</entry>
</row>
</tbody>
</tgroup>
</table>

92
doc/src/sgml/ref/alter_table.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.47 2002/07/31 17:19:50 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.48 2002/08/02 18:15:04 tgl Exp $
PostgreSQL documentation
-->
@ -23,6 +23,8 @@ PostgreSQL documentation
<synopsis>
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
ADD [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> <replaceable class="PARAMETER">type</replaceable> [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
DROP [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> [ RESTRICT | CASCADE ]
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> { SET DEFAULT <replaceable class="PARAMETER">value</replaceable> | DROP DEFAULT }
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]
@ -126,6 +128,26 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
</listitem>
</varlistentry>
<varlistentry>
<term>CASCADE</term>
<listitem>
<para>
Automatically drop objects that depend on the dropped column
or constraint (for example, views referencing the column).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>RESTRICT</term>
<listitem>
<para>
Refuse to drop the column or constraint if there are any dependent
objects. This is the default behavior.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
@ -186,6 +208,19 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
</listitem>
</varlistentry>
<varlistentry>
<term>DROP COLUMN</term>
<listitem>
<para>
This form drops a column from a table. Note that indexes and
table constraints involving the column will be automatically
dropped as well. You will need to say <literal>CASCADE</> if
anything outside the table depends on the column --- for example,
foreign key references, views, etc.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>SET/DROP DEFAULT</term>
<listitem>
@ -317,6 +352,22 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
form after you've entered non-null values for the column in all rows.
</para>
<para>
The <literal>DROP COLUMN</literal> command does not physically remove
the column, but simply makes it invisible to SQL operations. Subsequent
inserts and updates of the table will store a NULL for the column.
Thus, dropping a column is quick but it will not immediately reduce the
on-disk size of your table, as the space occupied
by the dropped column is not reclaimed. The space will be
reclaimed over time as existing rows are updated.
To reclaim the space at once, do a dummy <command>UPDATE</> of all rows
and then vacuum, as in:
<programlisting>
UPDATE table SET col = col;
VACUUM FULL table;
</programlisting>
</para>
<para>
Changing any part of the schema of a system
catalog is not permitted.
@ -342,6 +393,13 @@ ALTER TABLE distributors ADD COLUMN address VARCHAR(30);
</programlisting>
</para>
<para>
To drop a column from a table:
<programlisting>
ALTER TABLE distributors DROP COLUMN address RESTRICT;
</programlisting>
</para>
<para>
To rename an existing column:
<programlisting>
@ -420,38 +478,6 @@ ALTER TABLE distributors ADD PRIMARY KEY (dist_id);
The <literal>ALTER COLUMN</literal> form is in full compliance.
</para>
<para>
SQL92 specifies some additional capabilities for <command>ALTER TABLE</command>
statement which are not yet directly supported by <productname>PostgreSQL</productname>:
<variablelist>
<varlistentry>
<term>
<synopsis>
ALTER TABLE <replaceable class="PARAMETER">table</replaceable> DROP [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> { RESTRICT | CASCADE }
</synopsis>
</term>
<listitem>
<para>
Removes a column from a table.
Currently, to remove an existing column the table must be
recreated and reloaded:
<programlisting>
CREATE TABLE temp AS SELECT did, city FROM distributors;
DROP TABLE distributors;
CREATE TABLE distributors (
did DECIMAL(3) DEFAULT 1,
name VARCHAR(40) NOT NULL
);
INSERT INTO distributors SELECT * FROM temp;
DROP TABLE temp;
</programlisting>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
The clauses to rename tables, columns, indexes, and sequences are
<productname>PostgreSQL</productname> extensions from SQL92.

29
doc/src/sgml/ref/copy.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.34 2002/07/30 16:55:05 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.35 2002/08/02 18:15:04 tgl Exp $
PostgreSQL documentation
-->
@ -21,16 +21,14 @@ PostgreSQL documentation
<date>1999-12-11</date>
</refsynopsisdivinfo>
<synopsis>
COPY <replaceable class="parameter">table</replaceable>
[ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
FROM { '<replaceable class="parameter">filename</replaceable>' | <filename>stdin</filename> }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] '<replaceable class="parameter">delimiter</replaceable>' ]
[ NULL [ AS ] '<replaceable class="parameter">null string</replaceable>' ] ]
COPY <replaceable class="parameter">table</replaceable>
[ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
COPY <replaceable class="parameter">table</replaceable> [ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
TO { '<replaceable class="parameter">filename</replaceable>' | <filename>stdout</filename> }
[ [ WITH ]
[ BINARY ]
@ -201,10 +199,10 @@ ERROR: <replaceable>reason</replaceable>
<para>
If a list of columns is specified, <command>COPY</command> will
only copy the data in the specified columns to or from the table.
If there are any columns in the table that are not in the table,
<command>COPY FROM</command> will insert the default value for
that column.
only copy the data in the specified columns to or from the file.
If there are any columns in the table that are not in the file,
<command>COPY FROM</command> will insert the default values for
those columns.
</para>
<para>
@ -266,8 +264,8 @@ ERROR: <replaceable>reason</replaceable>
</para>
<para>
<command>COPY FROM</command> will invoke any triggers or check
constraints. However, it will not invoke rules.
<command>COPY FROM</command> will invoke any triggers and check
constraints on the destination table. However, it will not invoke rules.
</para>
<para>
@ -330,12 +328,9 @@ ERROR: <replaceable>reason</replaceable>
The attribute values themselves are strings generated by the
output function, or acceptable to the input function, of each
attribute's data type. The specified null-value string is used in
place of attributes that are NULL. When using <command>COPY
FROM</command> without a column list, each row of the input file
must contain data for each attribute in the table: no missing data
is allowed. Similarly, <command>COPY FROM</command> will raise
an error if it encounters any data in the input file that would
not be inserted into the table: extra data is not allowed.
place of attributes that are NULL.
<command>COPY FROM</command> will raise an error if any line of the
input file contains more or fewer columns than are expected.
</para>
<para>
If OIDS is specified, the OID is read or written as the first column,

4
doc/src/sgml/release.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.144 2002/07/29 22:14:10 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.145 2002/08/02 18:15:04 tgl Exp $
-->
<appendix id="release">
@ -24,6 +24,8 @@ CDATA means the content is "SGML-free", so you can write without
worries about funny characters.
-->
<literallayout><![CDATA[
COPY accepts a list of columns to copy
ALTER TABLE DROP COLUMN
CREATE OPERATOR CLASS/DROP OPERATOR CLASS
CREATE CAST/DROP CAST
Sequences created by SERIAL column definitions now auto-drop with the column