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Fix the problem that creating a user-defined type named _foo, followed by one

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named foo, would work but the other ordering would not.  If a user-specified
type or table name collides with an existing auto-generated array name, just
rename the array type out of the way by prepending more underscores.  This
should not create any backward-compatibility issues, since the cases in which
this will happen would have failed outright in prior releases.

Also fix an oversight in the arrays-of-composites patch: ALTER TABLE RENAME
renamed the table's rowtype but not its array type.
This commit is contained in:
Tom Lane
2007-05-12 00:55:00 +00:00
parent d8326119c8
commit 9aa3c782c9
8 changed files with 251 additions and 43 deletions
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35
doc/src/sgml/ref/create_type.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.70 2007/05/11 17:57:11 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.71 2007/05/12 00:54:59 tgl Exp $
PostgreSQL documentation
-->
@ -529,18 +529,6 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
<refsect1 id="SQL-CREATETYPE-notes">
<title>Notes</title>
<para>
It is best to avoid using type names that begin with the underscore
character (<literal>_</literal>). <productname>PostgreSQL</productname>
forms the name of an array type by prepending one or more underscores
to the element type's name, and these names may collide with user-defined
type names that begin with underscore. While the system will modify
generated array type names to avoid collisions, this does not help if the
conflicting array type already exists when you try to create your type.
Also, various old client software may assume that names beginning with
underscores always represent arrays.
</para>
<para>
Because there are no restrictions on use of a data type once it's been
created, creating a base type is tantamount to granting public execute
@ -552,6 +540,27 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
while converting it to or from external form.
</para>
<para>
Before <productname>PostgreSQL</productname> version 8.3, the name of
a generated array type was always exactly the element type's name with one
underscore character (<literal>_</literal>) prepended. (Type names were
therefore restricted in length to one less character than other names.)
While this is still usually the case, the array type name may vary from
this in case of maximum-length names or collisions with user type names
that begin with underscore. Writing code that depends on this convention
is therefore deprecated. Instead, use
<structname>pg_type</>.<structfield>typarray</> to locate the array type
associated with a given type.
</para>
<para>
It may be advisable to avoid using type and table names that begin with
underscore. While the server will change generated array type names to
avoid collisions with user-given names, there is still risk of confusion,
particularly with old client software that may assume that type names
beginning with underscores always represent arrays.
</para>
<para>
Before <productname>PostgreSQL</productname> version 8.2, the syntax
<literal>CREATE TYPE <replaceable>name</></literal> did not exist.