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Update release notes to show how to upgrade a database to use the new

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early binding for nextval() calls in default clauses.
This commit is contained in:
Bruce Momjian 2005-10-03 01:57:59 +00:00
parent 6a17577933
commit 07e74305fe
1 changed files with 62 additions and 10 deletions
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72
doc/src/sgml/release.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.381 2005/10/02 23:50:06 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.382 2005/10/03 01:57:59 momjian Exp $
Typical markup:
@ -262,6 +262,21 @@ pg_[A-Za-z0-9_] <application>
<itemizedlist>
<listitem>
<para>
<varname>Add proper sequence function dependencies (Tom)
</para>
<para>
In previous releases, <function>nextval()</>,
<function>currval</>, and <function>setval()</> recorded
sequence names as simple text strings, meaning that renaming or
dropping a sequence used in a <command>DEFAULT</> made the
clause invalid. This release stores all newly-created sequence
function arguments using internal oids, allowing them to handle
sequence renaming, and adding dependency information that
</para>
</listitem>
<listitem>
<para>
<varname>add_missing_from</> is now false by default (Neil)
@ -398,16 +413,53 @@ pg_[A-Za-z0-9_] <application>
</para>
<para>
When an expression like <literal>nextval('myseq')</> appears in a
column default expression or view, the referenced sequence (here
<literal>myseq</>) is now looked up immediately, and its pg_class
OID is placed in the stored expression. This representation will
survive renaming of the referenced sequence, as well as changes in
schema search paths. The system also understands that the sequence
reference represents a dependency, so the sequence cannot be dropped
without dropping the referencing object. To get the old behavior of
run-time lookup of the sequence by name, cast the argument to
<type>text</>, for example <literal>nextval('myseq'::text)</>.
column <command>DEFAULT</> expression or view, the referenced
sequence (here <literal>myseq</>) is now looked up immediately,
and its pg_class OID is placed in the stored expression. This
representation will survive renaming of the referenced sequence,
as well as changes in schema search paths. The system also
understands that the sequence reference represents a dependency,
so the sequence cannot be dropped without dropping the
referencing object. Previous releases stored this information as
a simple text string, with none of the benefits outlined above.
To get the old text-based behavior of run-time lookup of the
sequence name, cast the argument to <type>text</>, for example
<literal>nextval('myseq'::text)</>.
</para>
<para>
Pre-8.1 schemas loaded into 8.1 will use the previous, text-based
representation and therefore will not have these protections.
However, it is possible to upgrade a database to the newer
OID-based arguments. First, save this query into a file, such as
<filename>fixseq.sql</>:
<programlisting>
SELECT 'ALTER TABLE ' ||
pg_catalog.quote_ident(n.nspname) || '.' ||
pg_catalog.quote_ident(c.relname) ||
' ALTER COLUMN ' || pg_catalog.quote_ident(a.attname) ||
' SET DEFAULT ' ||
regexp_replace(d.adsrc, '(nextval\\(''[^'']*'')::text', '\\1', 'g') ||
';'
FROM pg_namespace n, pg_class c, pg_attribute a, pg_attrdef d
WHERE n.oid = c.relnamespace AND
c.oid = a.attrelid AND
a.attrelid = d.adrelid AND
a.attnum = d.adnum AND
d.adsrc ~ '.*nextval\\(''[^'']*''::text';
</programlisting>
Next, run the query against a database to find what
adjustments are required, like this for database <literal>db1</>:
<programlisting>
psql -aT -f fixseq.sql db1
</programlisting>
This will show the <command>ALTER TABLE</> commands needed to
convert the database to the newer OID-based representation.
Finally, run this to update the database:
<programlisting>
psql -aT -f fixseq.sql db1 | psql -e db1
</programlisting>
This process should be done for each database loaded with pre-8.1
schemas.
</listitem>
<listitem>