Re: [HACKERS] record identical operator - Review

[Steve Singer]

On 09/28/2013 03:03 PM, Kevin Grittner wrote:
<para>
+    To support matching of rows which include elements without a default
+    B-tree operator class, the following operators are defined for composite
+    type comparison:
+    <literal>*=</>,
+    <literal>*&lt;&gt;</>,
+    <literal>*&lt;</>,
+    <literal>*&lt;=</>,
+    <literal>*&gt;</>, and
+    <literal>*&gt;=</>.
+    These operators are also used internally to maintain materialized views,
+    and may be useful to replication software.  To ensure that all user
+    visible changes are detected, even when the equality operator for the
+    type treats old and new values as equal, the byte images of the stored
+    data are compared.  While ordering is deterministic, it is not generally
+    useful except to facilitate merge joins.  Ordering may differ between
+    system architectures and major releases of
+    <productname>PostgreSQL</productname>.
+   </para>

How about

 To support matching of rows which include elements without a default
    B-tree operator class, the following operators are defined for composite
    type comparison:
    <literal>*=</>,
    <literal>*&lt;&gt;</>,
    <literal>*&lt;</>,
    <literal>*&lt;=</>,
    <literal>*&gt;</>, and
   <literal>*&gt;=</>.

These operators compare the internal binary representation of the two 
rows.   Two rows might have a different binary representation even 
though comparisons of the two rows with the equality operator is true.   
The ordering of rows under these comparision operators is deterministic 
but not otherwise meaningful.  These operators are used internally for 
materialized views and might be useful for other specialized purposes 
such as replication but are not intended to be generally useful for 
writing queries.




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