"Ramanujam H S Iyengar" <hals_ramu@hotmail.com> writes:
> Can some one tell me what and when (Plan*)()->chgParam will contain ?
It's either an integer List or a Bitmapset, depending on what version
you are looking at, but in either case it contains the integer IDs of
PARAM_EXEC Param slots that have changed recently. This is used to
force recalculation of those plan nodes (and only those plan nodes)
that depend on the parameter(s) that have changed. AFAIR the PARAM_EXEC
mechanism is only used for passing values into and out of sub-selects,
but someday it might have more general use.
See the related plan fields extParam, allParam, setParam, parParam.
These are documented reasonably well (at least in current sources)
in plannodes.h and primnodes.h.
regards, tom lane