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Commiteb4b7a0

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author
Neil Conway
committed
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 onlypossible now that DELETE has a USING clause so that the user can joinother tables in a DELETE statement without relying on this behavior.
1 parentf53cd94 commiteb4b7a0

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6 files changed

+39
-56
lines changed

6 files changed

+39
-56
lines changed

‎doc/src/sgml/ref/delete.sgml

Lines changed: 1 addition & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.23 2005/04/07 01:51:37 neilc Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.24 2005/04/08 00:59:58 neilc Exp $
33
PostgreSQL documentation
44
-->
55

@@ -148,12 +148,6 @@ DELETE FROM films
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In some cases the join style is easier to write or faster to
149149
execute than the sub-select style.
150150
</para>
151-
152-
<para>
153-
If <varname>add_missing_from</varname> is enabled, any relations
154-
mentioned in the <literal>WHERE</literal> condition will be
155-
implicitly added to the <literal>USING</literal> clause.
156-
</para>
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</refsect1>
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<refsect1>

‎doc/src/sgml/ref/select.sgml

Lines changed: 13 additions & 34 deletions
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@@ -1,5 +1,5 @@
11
<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.82 2005/03/10 23:21:20 tgl Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.83 2005/04/08 00:59:58 neilc Exp $
33
PostgreSQL documentation
44
-->
55

@@ -1011,42 +1011,21 @@ SELECT 2+2;
10111011
</para>
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10131013
<para>
1014-
A less obvious use is to abbreviate a normal
1015-
<command>SELECT</command> from tables:
1014+
Note that if a <literal>FROM</literal> clause is not specified,
1015+
the query cannot reference any database tables. For example, the
1016+
following query is invalid:
10161017
<programlisting>
10171018
SELECT distributors.* WHERE distributors.name = 'Westward';
1018-
1019-
did | name
1020-
-----+----------
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108 | Westward
1022-
</programlisting>
1023-
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
1025-
<command>SELECT</command> statement but not mentioned in
1026-
<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
1031-
example, the command
1032-
<programlisting>
1033-
SELECT distributors.* FROM distributors d;
1034-
</programlisting>
1035-
is probably a mistake; most likely the user meant
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<programlisting>
1037-
SELECT d.* FROM distributors d;
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</programlisting>
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rather than the unconstrained join
1040-
<programlisting>
1041-
SELECT distributors.* FROM distributors d, distributors distributors;
10421019
</programlisting>
1043-
that he will actually get. To help detect this sort of mistake,
1044-
<productname>PostgreSQL</productname> will warn if the
1045-
implicit-<literal>FROM</literal> feature is used in a
1046-
<command>SELECT</command> statement that also contains an explicit
1047-
<literal>FROM</literal> clause. Also, it is possible to disable
1048-
the implicit-<literal>FROM</literal> feature by setting the
1049-
<xref linkend="guc-add-missing-from"> parameter to false.
1020+
<productname>PostgreSQL</productname> releases prior to
1021+
8.1 would accept queries of this form, and add an implicit entry
1022+
to the query's <literal>FROM</literal> clause for each table
1023+
referenced by the query. This is no longer the default behavior,
1024+
because it does not comply with the SQL standard, and is
1025+
considered by many to be error-prone. For compatibility with
1026+
applications that rely on this behavior the <xref
1027+
linkend="guc-add-missing-from"> configuration variable can be
1028+
enabled.
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</para>
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</refsect2>
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‎doc/src/sgml/ref/show.sgml

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.37 2005/01/04 03:58:16 tgl Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.38 2005/04/08 00:59:58 neilc Exp $
33
PostgreSQL documentation
44
-->
55

@@ -166,7 +166,7 @@ SHOW geqo;
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SHOW ALL;
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name | setting
168168
--------------------------------+----------------------------------------------
169-
add_missing_from |on
169+
add_missing_from |off
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archive_command | unset
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australian_timezones | off
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.

‎doc/src/sgml/runtime.sgml

Lines changed: 20 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
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$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.312 2005/03/29 03:01:29 tgl Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.313 2005/04/08 00:59:57 neilc Exp $
33
-->
44

55
<chapter Id="runtime">
@@ -3553,15 +3553,25 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
35533553
</indexterm>
35543554
<listitem>
35553555
<para>
3556-
When <literal>true</>, tables that are referenced by a query will be
3557-
automatically added to the <literal>FROM</> clause if not already
3558-
present. The default is <literal>true</> for compatibility with
3559-
previous releases of <productname>PostgreSQL</>. However, this
3560-
behavior is not SQL-standard, and many people dislike it because it
3561-
can mask mistakes (such as referencing a table where you should have
3562-
referenced its alias). Set to <literal>false</> for the SQL-standard
3563-
behavior of rejecting references to tables that are not listed in
3564-
<literal>FROM</>.
3556+
When <literal>true</>, tables that are referenced by a query
3557+
will be automatically added to the <literal>FROM</> clause if
3558+
not already present. This behavior does not comply with the
3559+
SQL standard and many people dislike it because it can mask
3560+
mistakes (such as referencing a table where you should have
3561+
referenced its alias). The default is <literal>false</>. This
3562+
variable can be enabled for compatibility with releases of
3563+
<productname>PostgreSQL</> prior to 8.1, where this behavior
3564+
was allowed by default.
3565+
</para>
3566+
3567+
<para>
3568+
Note that even when this variable is enabled, a warning
3569+
message will be emitted for each implicit <literal>FROM</>
3570+
entry referenced by a query. Users are encouraged to update
3571+
their applications to not rely on this behavior, by adding all
3572+
tables referenced by a query to the query's <literal>FROM</>
3573+
clause (or its <literal>USING</> clause in the case of
3574+
<command>DELETE</>).
35653575
</para>
35663576
</listitem>
35673577
</varlistentry>

‎src/backend/utils/misc/guc.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
* Written by Peter Eisentraut <peter_e@gmx.net>.
1111
*
1212
* IDENTIFICATION
13-
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.257 2005/03/25 16:17:27 tgl Exp $
13+
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.258 2005/04/08 00:59:59 neilc Exp $
1414
*
1515
*--------------------------------------------------------------------
1616
*/
@@ -791,7 +791,7 @@ static struct config_bool ConfigureNamesBool[] =
791791
NULL
792792
},
793793
&add_missing_from,
794-
true,NULL,NULL
794+
false,NULL,NULL
795795
},
796796
{
797797
{"check_function_bodies",PGC_USERSET,CLIENT_CONN_STATEMENT,

‎src/backend/utils/misc/postgresql.conf.sample

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -313,7 +313,7 @@
313313

314314
# - Previous Postgres Versions -
315315

316-
#add_missing_from =true
316+
#add_missing_from =false
317317
#regex_flavor = advanced# advanced, extended, or basic
318318
#sql_inheritance = true
319319
#default_with_oids = false

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