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Support MERGE into updatable views.

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This allows the target relation of MERGE to be an auto-updatable or
trigger-updatable view, and includes support for WITH CHECK OPTION,
security barrier views, and security invoker views.

A trigger-updatable view must have INSTEAD OF triggers for every type
of action (INSERT, UPDATE, and DELETE) mentioned in the MERGE command.
An auto-updatable view must not have any INSTEAD OF triggers. Mixing
auto-update and trigger-update actions (i.e., having a partial set of
INSTEAD OF triggers) is not supported.

Rule-updatable views are also not supported, since there is no
rewriter support for non-SELECT rules with MERGE operations.

Dean Rasheed, reviewed by Jian He and Alvaro Herrera.

Discussion: https://postgr.es/m/CAEZATCVcB1g0nmxuEc-A+gGB0HnfcGQNGYH7gS=7rq0u0zOBXA@mail.gmail.com
This commit is contained in:
Dean Rasheed
2024-02-29 15:56:59 +00:00
parent 8b29a119fd
commit 5f2e179bd3
23 changed files with 1380 additions and 288 deletions
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42
doc/src/sgml/ref/create_view.sgml
View File

@@ -192,12 +192,14 @@ CREATE VIEW [ <replaceable>schema</replaceable> . ] <replaceable>view_name</repl
<listitem>
<para>
This option controls the behavior of automatically updatable views. When
this option is specified, <command>INSERT</command> and <command>UPDATE</command>
this option is specified, <command>INSERT</command>,
<command>UPDATE</command>, and <command>MERGE</command>
commands on the view will be checked to ensure that new rows satisfy the
view-defining condition (that is, the new rows are checked to ensure that
they are visible through the view). If they are not, the update will be
rejected. If the <literal>CHECK OPTION</literal> is not specified,
<command>INSERT</command> and <command>UPDATE</command> commands on the view are
<command>INSERT</command>, <command>UPDATE</command>, and
<command>MERGE</command> commands on the view are
allowed to create rows that are not visible through the view. The
following check options are supported:
@@ -247,7 +249,8 @@ CREATE VIEW [ <replaceable>schema</replaceable> . ] <replaceable>view_name</repl
<command>INSERT</command> or <command>UPDATE</command> command to be rewritten, then
all check options will be ignored in the rewritten query, including any
checks from automatically updatable views defined on top of the relation
with the <literal>INSTEAD</literal> rule.
with the <literal>INSTEAD</literal> rule. <command>MERGE</command> is not
supported if the view or any of its base relations have rules.
</para>
</listitem>
</varlistentry>
@@ -360,7 +363,8 @@ CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
<para>
Simple views are automatically updatable: the system will allow
<command>INSERT</command>, <command>UPDATE</command> and <command>DELETE</command> statements
<command>INSERT</command>, <command>UPDATE</command>,
<command>DELETE</command>, and <command>MERGE</command> statements
to be used on the view in the same way as on a regular table. A view is
automatically updatable if it satisfies all of the following conditions:
@@ -400,13 +404,15 @@ CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
An automatically updatable view may contain a mix of updatable and
non-updatable columns. A column is updatable if it is a simple reference
to an updatable column of the underlying base relation; otherwise the
column is read-only, and an error will be raised if an <command>INSERT</command>
or <command>UPDATE</command> statement attempts to assign a value to it.
column is read-only, and an error will be raised if an
<command>INSERT</command>, <command>UPDATE</command>, or
<command>MERGE</command> statement attempts to assign a value to it.
</para>
<para>
If the view is automatically updatable the system will convert any
<command>INSERT</command>, <command>UPDATE</command> or <command>DELETE</command> statement
<command>INSERT</command>, <command>UPDATE</command>,
<command>DELETE</command>, or <command>MERGE</command> statement
on the view into the corresponding statement on the underlying base
relation. <command>INSERT</command> statements that have an <literal>ON
CONFLICT UPDATE</literal> clause are fully supported.
@@ -415,17 +421,21 @@ CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
<para>
If an automatically updatable view contains a <literal>WHERE</literal>
condition, the condition restricts which rows of the base relation are
available to be modified by <command>UPDATE</command> and <command>DELETE</command>
statements on the view. However, an <command>UPDATE</command> is allowed to
available to be modified by <command>UPDATE</command>,
<command>DELETE</command>, and <command>MERGE</command>
statements on the view. However, an <command>UPDATE</command> or
<command>MERGE</command> is allowed to
change a row so that it no longer satisfies the <literal>WHERE</literal>
condition, and thus is no longer visible through the view. Similarly,
an <command>INSERT</command> command can potentially insert base-relation rows
an <command>INSERT</command> or <command>MERGE</command> command can
potentially insert base-relation rows
that do not satisfy the <literal>WHERE</literal> condition and thus are not
visible through the view (<literal>ON CONFLICT UPDATE</literal> may
similarly affect an existing row not visible through the view).
The <literal>CHECK OPTION</literal> may be used to prevent
<command>INSERT</command> and <command>UPDATE</command> commands from creating
such rows that are not visible through the view.
<command>INSERT</command>, <command>UPDATE</command>, and
<command>MERGE</command> commands from creating such rows that are not
visible through the view.
</para>
<para>
@@ -443,14 +453,16 @@ CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
<para>
A more complex view that does not satisfy all these conditions is
read-only by default: the system will not allow an insert, update, or
delete on the view. You can get the effect of an updatable view by
read-only by default: the system will not allow an <command>INSERT</command>,
<command>UPDATE</command>, <command>DELETE</command>, or <command>MERGE</command>
on the view. You can get the effect of an updatable view by
creating <literal>INSTEAD OF</literal> triggers on the view, which must
convert attempted inserts, etc. on the view into appropriate actions
on other tables. For more information see <xref
linkend="sql-createtrigger"/>. Another possibility is to create rules
(see <xref linkend="sql-createrule"/>), but in practice triggers are
easier to understand and use correctly.
easier to understand and use correctly. Also note that <command>MERGE</command>
is not supported on relations with rules.
</para>
<para>