mirror of https://github.com/postgres/postgres
Change the default setting of "add_missing_from" to false. This has been
the long-term plan for this behavior for quite some time, but it is only possible now that DELETE has a USING clause so that the user can join other tables in a DELETE statement without relying on this behavior.
This commit is contained in:
Neil Conway
parent
f53cd94a78
commit
eb4b7a0b77
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.23 2005/04/07 01:51:37 neilc Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.24 2005/04/08 00:59:58 neilc Exp $
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PostgreSQL documentation
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-->
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@ -148,12 +148,6 @@ DELETE FROM films
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In some cases the join style is easier to write or faster to
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execute than the sub-select style.
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</para>
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<para>
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If <varname>add_missing_from</varname> is enabled, any relations
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mentioned in the <literal>WHERE</literal> condition will be
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implicitly added to the <literal>USING</literal> clause.
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</para>
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</refsect1>
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<refsect1>
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.82 2005/03/10 23:21:20 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.83 2005/04/08 00:59:58 neilc Exp $
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PostgreSQL documentation
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-->
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@ -1011,42 +1011,21 @@ SELECT 2+2;
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</para>
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<para>
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A less obvious use is to abbreviate a normal
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<command>SELECT</command> from tables:
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Note that if a <literal>FROM</literal> clause is not specified,
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the query cannot reference any database tables. For example, the
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following query is invalid:
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<programlisting>
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SELECT distributors.* WHERE distributors.name = 'Westward';
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did | name
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-----+----------
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108 | Westward
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</programlisting>
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This works because an implicit <literal>FROM</literal> item is
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added for each table that is referenced in other parts of the
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<command>SELECT</command> statement but not mentioned in
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<literal>FROM</literal>.
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</para>
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<para>
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While this is a convenient shorthand, it's easy to misuse. For
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example, the command
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<programlisting>
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SELECT distributors.* FROM distributors d;
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</programlisting>
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is probably a mistake; most likely the user meant
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<programlisting>
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SELECT d.* FROM distributors d;
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</programlisting>
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rather than the unconstrained join
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<programlisting>
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SELECT distributors.* FROM distributors d, distributors distributors;
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</programlisting>
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that he will actually get. To help detect this sort of mistake,
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<productname>PostgreSQL</productname> will warn if the
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implicit-<literal>FROM</literal> feature is used in a
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<command>SELECT</command> statement that also contains an explicit
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<literal>FROM</literal> clause. Also, it is possible to disable
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the implicit-<literal>FROM</literal> feature by setting the
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<xref linkend="guc-add-missing-from"> parameter to false.
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<productname>PostgreSQL</productname> releases prior to
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8.1 would accept queries of this form, and add an implicit entry
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to the query's <literal>FROM</literal> clause for each table
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referenced by the query. This is no longer the default behavior,
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because it does not comply with the SQL standard, and is
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considered by many to be error-prone. For compatibility with
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applications that rely on this behavior the <xref
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linkend="guc-add-missing-from"> configuration variable can be
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enabled.
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</para>
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</refsect2>
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.37 2005/01/04 03:58:16 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.38 2005/04/08 00:59:58 neilc Exp $
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PostgreSQL documentation
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-->
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@ -166,7 +166,7 @@ SHOW geqo;
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SHOW ALL;
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name | setting
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--------------------------------+----------------------------------------------
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add_missing_from | on
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add_missing_from | off
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archive_command | unset
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australian_timezones | off
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.
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.312 2005/03/29 03:01:29 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.313 2005/04/08 00:59:57 neilc Exp $
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-->
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<chapter Id="runtime">
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@ -3553,15 +3553,25 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
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</indexterm>
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<listitem>
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<para>
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When <literal>true</>, tables that are referenced by a query will be
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automatically added to the <literal>FROM</> clause if not already
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present. The default is <literal>true</> for compatibility with
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previous releases of <productname>PostgreSQL</>. However, this
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behavior is not SQL-standard, and many people dislike it because it
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can mask mistakes (such as referencing a table where you should have
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referenced its alias). Set to <literal>false</> for the SQL-standard
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behavior of rejecting references to tables that are not listed in
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<literal>FROM</>.
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When <literal>true</>, tables that are referenced by a query
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will be automatically added to the <literal>FROM</> clause if
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not already present. This behavior does not comply with the
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SQL standard and many people dislike it because it can mask
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mistakes (such as referencing a table where you should have
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referenced its alias). The default is <literal>false</>. This
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variable can be enabled for compatibility with releases of
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<productname>PostgreSQL</> prior to 8.1, where this behavior
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was allowed by default.
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</para>
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<para>
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Note that even when this variable is enabled, a warning
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message will be emitted for each implicit <literal>FROM</>
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entry referenced by a query. Users are encouraged to update
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their applications to not rely on this behavior, by adding all
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tables referenced by a query to the query's <literal>FROM</>
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clause (or its <literal>USING</> clause in the case of
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<command>DELETE</>).
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</para>
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</listitem>
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</varlistentry>
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@ -10,7 +10,7 @@
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* Written by Peter Eisentraut <peter_e@gmx.net>.
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.257 2005/03/25 16:17:27 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.258 2005/04/08 00:59:59 neilc Exp $
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*
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*--------------------------------------------------------------------
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*/
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@ -791,7 +791,7 @@ static struct config_bool ConfigureNamesBool[] =
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NULL
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},
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&add_missing_from,
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true, NULL, NULL
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false, NULL, NULL
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},
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{
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{"check_function_bodies", PGC_USERSET, CLIENT_CONN_STATEMENT,
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@ -313,7 +313,7 @@
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# - Previous Postgres Versions -
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#add_missing_from = true
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#add_missing_from = false
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#regex_flavor = advanced # advanced, extended, or basic
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#sql_inheritance = true
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#default_with_oids = false
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