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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2016-12-23 12:53:09 -0500 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2016-12-23 12:53:09 -0500 |
| commit | 3c9d398484fb6e188e665be8299d6e5e89924c94 (patch) | |
| tree | f5ee6501f3c21440d194f89b950525ff9dac2b36 | |
| parent | ff33d1456ea098e160cbbc74b332656c06abc2ab (diff) | |
| download | postgresql-3c9d398484fb6e188e665be8299d6e5e89924c94.tar.gz postgresql-3c9d398484fb6e188e665be8299d6e5e89924c94.zip | |
Doc: improve index entry for "median".
We had an index entry for "median" attached to the percentile_cont function
entry, which was pretty useless because a person following the link would
never realize that that function was the one they were being hinted to use.
Instead, make the index entry point at the example in syntax-aggregates,
and add a <seealso> link to "percentile".
Also, since that example explicitly claims to be calculating the median,
make it use percentile_cont not percentile_disc. This makes no difference
in terms of the larger goals of that section, but so far as I can find,
nearly everyone thinks that "median" means the continuous not discrete
calculation.
Per gripe from Steven Winfield. Back-patch to 9.4 where we introduced
percentile_cont.
Discussion: https://postgr.es/m/20161223102056.25614.1166@wrigleys.postgresql.org
| -rw-r--r-- | doc/src/sgml/func.sgml | 3 | ||||
| -rw-r--r-- | doc/src/sgml/syntax.sgml | 14 |
2 files changed, 12 insertions, 5 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 0f9c9bf1296..10e31868baf 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -13774,9 +13774,6 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab; <primary>percentile</primary> <secondary>continuous</secondary> </indexterm> - <indexterm> - <primary>median</primary> - </indexterm> <function>percentile_cont(<replaceable class="parameter">fraction</replaceable>) WITHIN GROUP (ORDER BY <replaceable class="parameter">sort_expression</replaceable>)</function> </entry> <entry> diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml index 000da39250f..4ea667bd52f 100644 --- a/doc/src/sgml/syntax.sgml +++ b/doc/src/sgml/syntax.sgml @@ -1694,11 +1694,21 @@ SELECT string_agg(a ORDER BY a, ',') FROM table; -- incorrect case, write just <literal>()</> not <literal>(*)</>. (<productname>PostgreSQL</> will actually accept either spelling, but only the first way conforms to the SQL standard.) + </para> + + <para> + <indexterm> + <primary>median</primary> + </indexterm> + <indexterm> + <primary>median</primary> + <seealso>percentile</seealso> + </indexterm> An example of an ordered-set aggregate call is: <programlisting> -SELECT percentile_disc(0.5) WITHIN GROUP (ORDER BY income) FROM households; - percentile_disc +SELECT percentile_cont(0.5) WITHIN GROUP (ORDER BY income) FROM households; + percentile_cont ----------------- 50489 </programlisting> |