        If set, logs system resource usage statistics (memory and CPU) on
        various B-tree operations.
       </P
><P
>        This parameter is only available if the <TT
CLASS="SYMBOL"
>BTREE_BUILD_STATS</TT
>
        macro was defined when <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> was
        compiled.
       </P
></DD
><DT
><A
NAME="GUC-WAL-DEBUG"
></A
><TT
CLASS="VARNAME"
>wal_debug</TT
> (<TT
CLASS="TYPE"
>boolean</TT
>)</DT
><DD
><P
>        If on, emit WAL-related debugging output. This par