The below code worked for me... pasting it here (May be helpful for someone)
Relation heap; ItemPointer ht_ctid; heap = heap_open(50620, AccessShareLock); /* 50620 - Table/Relation Oid - Hardcoded for better understanding */
ScanKeyInit(&skey, 1, BTEqualStrategyNumber, F_INT8EQ, Int64GetDatum(100)); /* 100 is the Value of PK of which i'm doing a lookup*/ scan = systable_beginscan(heap, 50624 , true, NULL, 1, &skey); // 50624 is the Oid of PKIndex for this Table/Relation.
PS: You have to use different Procedure(F_INT8EQ/F_TEXTEQ etc..) and Datum Conversion functions(Int64GetDatum/CStringGetTextDatum etc..) in ScanKeyInit() function as per your PK Data Types.
Michael Paquier <michael.paquier@gmail.com> writes: > On Tue, May 2, 2017 at 6:12 PM, Mahi Gurram <teckymahi@gmail.com> wrote: >> Please suggest me the easiest way to lookup into PK's B-Tree index for >> getting TIDs.
> Why don't you just use SPI within your extension? No need to copy the > logic for btree lookups this way.
There's not actually that much code needed, though -- basically index_beginscan, index_rescan, index_getnext, index_endscan. One possible model to follow is systable_beginscan and friends, in genam.c.
I think that you could possibly get away with just applying systable_beginscan to random user tables, even. But it's at least a conceptual mismatch, and there are some things in there, like the test on IgnoreSystemIndexes, that you probably don't want.