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28th chunk of `doc/src/sgml/xfunc.sgml`
2fde97d8baeb0f51528da0e77a847ef862b4cf0b90f664cd0000000100000fa1
  <row>
         <entry><type>int8</type> (<type>bigint</type>)</entry>
         <entry><type>int64</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
        <row>
         <entry><type>interval</type></entry>
         <entry><type>Interval*</type></entry>
         <entry><filename>datatype/timestamp.h</filename></entry>
        </row>
        <row>
         <entry><type>lseg</type></entry>
         <entry><type>LSEG*</type></entry>
         <entry><filename>utils/geo_decls.h</filename></entry>
        </row>
        <row>
         <entry><type>name</type></entry>
         <entry><type>Name</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
        <row>
         <entry><type>numeric</type></entry>
         <entry><type>Numeric</type></entry>
         <entry><filename>utils/numeric.h</filename></entry>
        </row>
        <row>
         <entry><type>oid</type></entry>
         <entry><type>Oid</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
        <row>
         <entry><type>oidvector</type></entry>
         <entry><type>oidvector*</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
        <row>
         <entry><type>path</type></entry>
         <entry><type>PATH*</type></entry>
         <entry><filename>utils/geo_decls.h</filename></entry>
        </row>
        <row>
         <entry><type>point</type></entry>
         <entry><type>POINT*</type></entry>
         <entry><filename>utils/geo_decls.h</filename></entry>
        </row>
        <row>
         <entry><type>regproc</type></entry>
         <entry><type>RegProcedure</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
        <row>
         <entry><type>text</type></entry>
         <entry><type>text*</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
        <row>
         <entry><type>tid</type></entry>
         <entry><type>ItemPointer</type></entry>
         <entry><filename>storage/itemptr.h</filename></entry>
        </row>
        <row>
         <entry><type>time</type></entry>
         <entry><type>TimeADT</type></entry>
         <entry><filename>utils/date.h</filename></entry>
        </row>
        <row>
         <entry><type>time with time zone</type></entry>
         <entry><type>TimeTzADT</type></entry>
         <entry><filename>utils/date.h</filename></entry>
        </row>
        <row>
         <entry><type>timestamp</type></entry>
         <entry><type>Timestamp</type></entry>
         <entry><filename>datatype/timestamp.h</filename></entry>
        </row>
        <row>
         <entry><type>timestamp with time zone</type></entry>
         <entry><type>TimestampTz</type></entry>
         <entry><filename>datatype/timestamp.h</filename></entry>
        </row>
        <row>
         <entry><type>varchar</type></entry>
         <entry><type>VarChar*</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
        <row>
         <entry><type>xid</type></entry>
         <entry><type>TransactionId</type></entry>
         <entry><filename>postgres.h</filename></entry>
        </row>
       </tbody>
      </tgroup>
     </table>

    <para>
     Now that we've gone over all of the possible structures
     for base types, we can show some examples of real functions.
    </para>
   </sect2>

   <sect2 id="xfunc-c-v1-call-conv">
    <title>Version 1 Calling Conventions</title>

    <para>
     The version-1 calling convention relies on macros to suppress most
     of the complexity of passing arguments and results.  The C declaration
     of a version-1 function is always:
<programlisting>
Datum funcname(PG_FUNCTION_ARGS)
</programlisting>
     In addition, the macro call:
<programlisting>
PG_FUNCTION_INFO_V1(funcname);
</programlisting>
     must appear in the same source file.  (Conventionally, it's
     written just before
Title: Equivalent C Types for Built-in SQL Types in PostgreSQL (Part 2) and Version 1 Calling Conventions
Summary
This section continues the table mapping SQL data types to their corresponding C types in PostgreSQL, including oidvector, path, point, regproc, text, tid, time, time with time zone, timestamp, timestamp with time zone, varchar, and xid. It also introduces the version-1 calling convention for C functions used in PostgreSQL, which relies on macros to handle argument passing and result retrieval. It highlights the required function declaration format `Datum funcname(PG_FUNCTION_ARGS)` and the mandatory `PG_FUNCTION_INFO_V1(funcname)` macro call in the same source file.