On Tue, Aug 2, 2011 at 3:45 PM, Heikki Linnakangas < heikki.linnakan...@enterprisedb.com> wrote:
> On 02.08.2011 12:54, Ashutosh Bapat wrote: > >> Hi All, >> I am looking at usage of bound parameters. >> >> In functions SPI_cursor_open_with_args() and SPI_cursor_open_with_args() >> parameters are flagged as constants and passed to the planner in following >> manner, >> paramLI = _SPI_convert_params(nargs, argtypes, >> Values, Nulls, >> PARAM_FLAG_CONST); >> >> _SPI_prepare_plan(src,&plan, paramLI); >> >> The bound params "paramLI" are then passed to the planner as boundParams. >> Before actually planning the query, these parameters are evaluated duing >> constant evaluation (eval_const_expressions_**mutator()), and the Param >> nodes >> are replaced with Constant nodes. >> Further, while executing such queries we pass the paramLI structure to the >> execution routine e.g. _SPI_execute_plan(). These parameter values are >> stored in "EState" structure. But, since these parameters are already >> folded >> into queries, it looks like parameter values stored in EState are never >> used. >> >> Is this correct? Or somewhere we use those parameter values? >> > > That is correct, at the moment. PARAM_FLAG_CONST means that the planner is > free evaluate the params during planning, but it doesn't have to. You still > need to pass the params in _SPI_execute_plan() in case the planner decided > to not convert some params to Consts, even though as the code stands today > it always will. > Ok, thanks. > > -- > Heikki Linnakangas > EnterpriseDB http://www.enterprisedb.com > -- Best Wishes, Ashutosh Bapat EntepriseDB Corporation The Enterprise Postgres Company
