Doc: clarify behavior of row-limit arguments in the PLs' SPI wrappers.

plperl, plpython, and pltcl all provide query-execution functions
that are thin wrappers around SPI_execute() or its variants.
The SPI functions document their row-count limit arguments clearly,
as "maximum number of rows to return, or 0 for no limit".  However
the PLs' documentation failed to explain this special behavior of
zero, so that a reader might well assume it means "fetch zero
rows".  Improve that.

Daniel Gustafsson and Tom Lane, per report from Kieran McCusker

Discussion: https://postgr.es/m/CAGgUQ6H6qYScctOhktQ9HLFDDoafBKHyUgJbZ6q_dOApnzNTXg@mail.gmail.com

1 files changed, 5 insertions, 3 deletions

diff --git a/doc/src/sgml/pltcl.sgml b/doc/src/sgml/pltcl.sgml
index bf56ba6b1c..b31f2c1330 100644
--- a/doc/src/sgml/pltcl.sgml
+++ b/doc/src/sgml/pltcl.sgml
@@ -341,9 +341,11 @@ $$ LANGUAGE pltcl;
        </para>
        <para>
         The optional <literal>-count</literal> value tells
-        <function>spi_exec</function> the maximum number of rows
-        to process in the command.  The effect of this is comparable to
-        setting up a query as a cursor and then saying <literal>FETCH <replaceable>n</replaceable></literal>.
+        <function>spi_exec</function> to stop
+        once <replaceable>n</replaceable> rows have been retrieved,
+        much as if the query included a <literal>LIMIT</literal> clause.
+        If <replaceable>n</replaceable> is zero, the query is run to
+        completion, the same as when <literal>-count</literal> is omitted.
        </para>
        <para>
         If the command is a <command>SELECT</command> statement, the values of the