/*
* GetFdwRoutineForRelation - look up the handler of the foreign-data wrapper
* for the given foreign table, and retrieve its FdwRoutine struct.
*
* This function is preferred over GetFdwRoutineByRelId because it caches
* the data in the relcache entry, saving a number of catalog lookups.
*
* If makecopy is true then the returned data is freshly palloc'd in the
* caller's memory context. Otherwise, it's a pointer to the relcache data,
* which will be lost in any relcache reset --- so don't rely on it long.
*/
FdwRoutine *
GetFdwRoutineForRelation(Relation relation, bool makecopy)
{
FdwRoutine *fdwroutine;
FdwRoutine *cfdwroutine;
if (relation->rd_fdwroutine == NULL)
{
/* Get the info by consulting the catalogs and the FDW code */
fdwroutine = GetFdwRoutineByRelId(RelationGetRelid(relation));
/* Save the data for later reuse in CacheMemoryContext */
cfdwroutine = (FdwRoutine *) MemoryContextAlloc(CacheMemoryContext,
sizeof(FdwRoutine));
memcpy(cfdwroutine, fdwroutine, sizeof(FdwRoutine));
relation->rd_fdwroutine = cfdwroutine;
/* Give back the locally palloc'd copy regardless of makecopy */
return fdwroutine;
}
/* We have valid cached data --- does the caller want a copy? */
if (makecopy)
{
fdwroutine = (FdwRoutine *) palloc(sizeof(FdwRoutine));
memcpy(fdwroutine, relation->rd_fdwroutine, sizeof(FdwRoutine));
return fdwroutine;
}
/* Only a short-lived reference is needed, so just hand back cached copy */
return relation->rd_fdwroutine;
}
/* ----------------------------------------------------------------
* ExecInitForeignScan
* ----------------------------------------------------------------
*/
ForeignScanState *
ExecInitForeignScan(ForeignScan *node, EState *estate, int eflags)
{
ForeignScanState *scanstate;
Relation currentRelation;
FdwRoutine *fdwroutine;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
/*
* create state structure
*/
scanstate = makeNode(ForeignScanState);
scanstate->ss.ps.plan = (Plan *) node;
scanstate->ss.ps.state = estate;
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &scanstate->ss.ps);
scanstate->ss.ps.ps_TupFromTlist = false;
/*
* initialize child expressions
*/
scanstate->ss.ps.targetlist = (List *)
ExecInitExpr((Expr *) node->scan.plan.targetlist,
(PlanState *) scanstate);
scanstate->ss.ps.qual = (List *)
ExecInitExpr((Expr *) node->scan.plan.qual,
(PlanState *) scanstate);
/*
* tuple table initialization
*/
ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
ExecInitScanTupleSlot(estate, &scanstate->ss);
/*
* open the base relation and acquire appropriate lock on it.
*/
currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid);
scanstate->ss.ss_currentRelation = currentRelation;
/*
* get the scan type from the relation descriptor.
*/
ExecAssignScanType(&scanstate->ss, RelationGetDescr(currentRelation));
/*
* Initialize result tuple type and projection info.
*/
ExecAssignResultTypeFromTL(&scanstate->ss.ps);
ExecAssignScanProjectionInfo(&scanstate->ss);
/*
* Acquire function pointers from the FDW's handler, and init fdw_state.
*/
fdwroutine = GetFdwRoutineByRelId(RelationGetRelid(currentRelation));
scanstate->fdwroutine = fdwroutine;
scanstate->fdw_state = NULL;
/*
* Tell the FDW to initiate the scan.
*/
fdwroutine->BeginForeignScan(scanstate, eflags);
return scanstate;
}
/* ----------------------------------------------------------------
* ExecInitForeignScan
* ----------------------------------------------------------------
*/
foreign_ss *
ExecInitForeignScan(foreign_scan_sc *node, exec_state_n *estate, int eflags)
{
foreign_ss* scanstate;
struct relation* currentRelation;
FdwRoutine *fdwroutine;
/* check for unsupported flags */
ASSERT(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
/*
* create state structure
*/
scanstate = MK_N(ForeignScanState,foreign_ss);
scanstate->ss.ps.plan = (plan_n *) node;
scanstate->ss.ps.state = estate;
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &scanstate->ss.ps);
scanstate->ss.ps.ps_TupFromTlist = false;
/*
* initialize child expressions
*/
scanstate->ss.ps.targetlist = (struct list *) exec_init_expr(
(expr_n *) node->scan.plan.targetlist,
(plan_state_n *) scanstate);
scanstate->ss.ps.qual = (struct list *) exec_init_expr(
(expr_n *) node->scan.plan.qual,
(plan_state_n *) scanstate);
/*
* tuple table initialization
*/
exec_init_result_tupslot(estate, &scanstate->ss.ps);
exec_init_scan_tupslot(estate, &scanstate->ss);
/*
* open the base relation and acquire appropriate lock on it.
*/
currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid);
scanstate->ss.ss_currentRelation = currentRelation;
/*
* get the scan type from the relation descriptor.
*/
ExecAssignScanType(&scanstate->ss, REL_DESC(currentRelation));
/*
* Initialize result tuple type and projection info.
*/
ExecAssignResultTypeFromTL(&scanstate->ss.ps);
ExecAssignScanProjectionInfo(&scanstate->ss);
/*
* Acquire function pointers from the FDW's handler, and init fdw_state.
*/
fdwroutine = GetFdwRoutineByRelId(REL_ID(currentRelation));
scanstate->fdwroutine = fdwroutine;
scanstate->fdw_state = NULL;
/*
* Tell the FDW to initiate the scan.
*/
fdwroutine->BeginForeignScan(scanstate, eflags);
return scanstate;
}
