Re: Another modest proposal for docs formatting: catalog descriptions

Here's a really quick-n-dirty prototype patch that just converts the
pg_aggregate table to the proposed style, plus a screenshot for those
who don't feel like actually building the docs with the patch.

Looking at the results, it seems like we could really use a bit more
horizontal space between the column names and data types, and perhaps
also between the types and the (references) annotations.  Other than
that it looks decent.  I don't know what's the cleanest way to add
some space there --- I'd rather not have the SGML text do it explicitly.

There's room for complaint that this takes up more vertical space than
the old way, assuming you have a reasonably wide window.  I'm not
terribly bothered by that, but maybe someone else will be?  I'm inclined
to think that that's well worth the benefit that we won't feel compelled
to keep column descriptions short.

BTW, this being just a test hack, I repurposed the "func_table_entry" and
"func_signature" style marker roles.  If we do this for real then of
course we'd want to use different roles, even if they happen to mark up
the same for now.

            regards, tom lane

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index ce33df9..efb5e64 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -388,178 +388,251 @@

   <table>
    <title><structname>pg_aggregate</structname> Columns</title>
-
-   <tgroup cols="4">
+   <tgroup cols="1">
     <thead>
      <row>
-      <entry>Name</entry>
-      <entry>Type</entry>
-      <entry>References</entry>
-      <entry>Description</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
      </row>
     </thead>
+
     <tbody>
      <row>
-      <entry><structfield>aggfnoid</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry><structname>pg_proc</structname> OID of the aggregate function</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggfnoid</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       <structname>pg_proc</structname> OID of the aggregate function
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggkind</structfield></entry>
-      <entry><type>char</type></entry>
-      <entry></entry>
-      <entry>Aggregate kind:
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggkind</structfield>
+       <type>char</type>
+      </para>
+      <para>
+       Aggregate kind:
        <literal>n</literal> for <quote>normal</quote> aggregates,
        <literal>o</literal> for <quote>ordered-set</quote> aggregates, or
        <literal>h</literal> for <quote>hypothetical-set</quote> aggregates
-      </entry>
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggnumdirectargs</structfield></entry>
-      <entry><type>int2</type></entry>
-      <entry></entry>
-      <entry>Number of direct (non-aggregated) arguments of an ordered-set or
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggnumdirectargs</structfield>
+       <type>int2</type>
+      </para>
+      <para>
+       Number of direct (non-aggregated) arguments of an ordered-set or
        hypothetical-set aggregate, counting a variadic array as one argument.
        If equal to <structfield>pronargs</structfield>, the aggregate must be variadic
        and the variadic array describes the aggregated arguments as well as
        the final direct arguments.
-       Always zero for normal aggregates.</entry>
+       Always zero for normal aggregates.
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggtransfn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Transition function</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggtransfn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Transition function
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggfinalfn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Final function (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggfinalfn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Final function (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggcombinefn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Combine function (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggcombinefn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Combine function (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggserialfn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Serialization function (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggserialfn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Serialization function (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggdeserialfn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Deserialization function (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggdeserialfn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Deserialization function (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggmtransfn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Forward transition function for moving-aggregate mode (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggmtransfn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Forward transition function for moving-aggregate mode (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggminvtransfn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Inverse transition function for moving-aggregate mode (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggminvtransfn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Inverse transition function for moving-aggregate mode (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggmfinalfn</structfield></entry>
-      <entry><type>regproc</type></entry>
-      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
-      <entry>Final function for moving-aggregate mode (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggmfinalfn</structfield>
+       <type>regproc</type>
+       (references <link
linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Final function for moving-aggregate mode (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggfinalextra</structfield></entry>
-      <entry><type>bool</type></entry>
-      <entry></entry>
-      <entry>True to pass extra dummy arguments to <structfield>aggfinalfn</structfield></entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggfinalextra</structfield>
+       <type>bool</type>
+      </para>
+      <para>
+       True to pass extra dummy arguments to <structfield>aggfinalfn</structfield>
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggmfinalextra</structfield></entry>
-      <entry><type>bool</type></entry>
-      <entry></entry>
-      <entry>True to pass extra dummy arguments to <structfield>aggmfinalfn</structfield></entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggmfinalextra</structfield>
+       <type>bool</type>
+      </para>
+      <para>
+       True to pass extra dummy arguments to <structfield>aggmfinalfn</structfield>
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggfinalmodify</structfield></entry>
-      <entry><type>char</type></entry>
-      <entry></entry>
-      <entry>Whether <structfield>aggfinalfn</structfield> modifies the
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggfinalmodify</structfield>
+       <type>char</type>
+      </para>
+      <para>
+       Whether <structfield>aggfinalfn</structfield> modifies the
        transition state value:
        <literal>r</literal> if it is read-only,
        <literal>s</literal> if the <structfield>aggtransfn</structfield>
        cannot be applied after the <structfield>aggfinalfn</structfield>, or
        <literal>w</literal> if it writes on the value
-      </entry>
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggmfinalmodify</structfield></entry>
-      <entry><type>char</type></entry>
-      <entry></entry>
-      <entry>Like <structfield>aggfinalmodify</structfield>, but for
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggmfinalmodify</structfield>
+       <type>char</type>
+      </para>
+      <para>
+       Like <structfield>aggfinalmodify</structfield>, but for
        the <structfield>aggmfinalfn</structfield>
-      </entry>
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggsortop</structfield></entry>
-      <entry><type>oid</type></entry>
-      <entry><literal><link
linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.oid</literal></entry>
-      <entry>Associated sort operator (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggsortop</structfield>
+       <type>oid</type>
+       (references <link
linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Associated sort operator (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggtranstype</structfield></entry>
-      <entry><type>oid</type></entry>
-      <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
-      <entry>Data type of the aggregate function's internal transition (state) data</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggtranstype</structfield>
+       <type>oid</type>
+       (references <link
linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Data type of the aggregate function's internal transition (state) data
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggtransspace</structfield></entry>
-      <entry><type>int4</type></entry>
-      <entry></entry>
-      <entry>Approximate average size (in bytes) of the transition state
-       data, or zero to use a default estimate</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggtransspace</structfield>
+       <type>int4</type>
+      </para>
+      <para>
+       Approximate average size (in bytes) of the transition state
+       data, or zero to use a default estimate
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggmtranstype</structfield></entry>
-      <entry><type>oid</type></entry>
-      <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
-      <entry>Data type of the aggregate function's internal transition (state)
-       data for moving-aggregate mode (zero if none)</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggmtranstype</structfield>
+       <type>oid</type>
+       (references <link
linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
+      </para>
+      <para>
+       Data type of the aggregate function's internal transition (state)
+       data for moving-aggregate mode (zero if none)
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggmtransspace</structfield></entry>
-      <entry><type>int4</type></entry>
-      <entry></entry>
-      <entry>Approximate average size (in bytes) of the transition state data
-       for moving-aggregate mode, or zero to use a default estimate</entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggmtransspace</structfield>
+       <type>int4</type>
+      </para>
+      <para>
+       Approximate average size (in bytes) of the transition state data
+       for moving-aggregate mode, or zero to use a default estimate
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>agginitval</structfield></entry>
-      <entry><type>text</type></entry>
-      <entry></entry>
-      <entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>agginitval</structfield>
+       <type>text</type>
+      </para>
+      <para>
        The initial value of the transition state.  This is a text
        field containing the initial value in its external string
        representation.  If this field is null, the transition state
        value starts out null.
-      </entry>
+      </para></entry>
      </row>
      <row>
-      <entry><structfield>aggminitval</structfield></entry>
-      <entry><type>text</type></entry>
-      <entry></entry>
-      <entry>
+      <entry role="func_table_entry"><para role="func_signature">
+       <structfield>aggminitval</structfield>
+       <type>text</type>
+      </para>
+      <para>
        The initial value of the transition state for moving-aggregate mode.
        This is a text field containing the initial value in its external
        string representation.  If this field is null, the transition state
        value starts out null.
-      </entry>
+      </para></entry>
      </row>
     </tbody>
    </tgroup>