Restructure index access method API to hide most of it at the C level.

This patch reduces pg_am to just two columns, a name and a handler
function.  All the data formerly obtained from pg_am is now provided
in a C struct returned by the handler function.  This is similar to
the designs we've adopted for FDWs and tablesample methods.  There
are multiple advantages.  For one, the index AM's support functions
are now simple C functions, making them faster to call and much less
error-prone, since the C compiler can now check function signatures.
For another, this will make it far more practical to define index access
methods in installable extensions.

A disadvantage is that SQL-level code can no longer see attributes
of index AMs; in particular, some of the crosschecks in the opr_sanity
regression test are no longer possible from SQL.  We've addressed that
by adding a facility for the index AM to perform such checks instead.
(Much more could be done in that line, but for now we're content if the
amvalidate functions more or less replace what opr_sanity used to do.)
We might also want to expose some sort of reporting functionality, but
this patch doesn't do that.

Alexander Korotkov, reviewed by Petr Jelínek, and rather heavily
editorialized on by me.

8 files changed, 225 insertions, 103 deletions

diff --git a/src/backend/access/gist/Makefile b/src/backend/access/gist/Makefile
index cc9468ffb19..21875bf7aee 100644
--- a/src/backend/access/gist/Makefile
+++ b/src/backend/access/gist/Makefile
@@ -13,6 +13,6 @@ top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = gist.o gistutil.o gistxlog.o gistvacuum.o gistget.o gistscan.o \
-       gistproc.o gistsplit.o gistbuild.o gistbuildbuffers.o
+       gistproc.o gistsplit.o gistbuild.o gistbuildbuffers.o gistvalidate.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 834d9d33358..996363c2ded 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -14,17 +14,15 @@
  */
 #include "postgres.h"
 
-#include "access/genam.h"
 #include "access/gist_private.h"
-#include "access/xloginsert.h"
-#include "catalog/index.h"
+#include "access/gistscan.h"
 #include "catalog/pg_collation.h"
 #include "miscadmin.h"
-#include "storage/bufmgr.h"
-#include "storage/indexfsm.h"
+#include "utils/index_selfuncs.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
 
+
 /* non-export function prototypes */
 static void gistfixsplit(GISTInsertState *state, GISTSTATE *giststate);
 static bool gistinserttuple(GISTInsertState *state, GISTInsertStack *stack,
@@ -50,6 +48,50 @@ static void gistvacuumpage(Relation rel, Page page, Buffer buffer);
 
 
 /*
+ * GiST handler function: return IndexAmRoutine with access method parameters
+ * and callbacks.
+ */
+Datum
+gisthandler(PG_FUNCTION_ARGS)
+{
+	IndexAmRoutine *amroutine = makeNode(IndexAmRoutine);
+
+	amroutine->amstrategies = 0;
+	amroutine->amsupport = 9;
+	amroutine->amcanorder = false;
+	amroutine->amcanorderbyop = true;
+	amroutine->amcanbackward = false;
+	amroutine->amcanunique = false;
+	amroutine->amcanmulticol = true;
+	amroutine->amoptionalkey = true;
+	amroutine->amsearcharray = false;
+	amroutine->amsearchnulls = true;
+	amroutine->amstorage = true;
+	amroutine->amclusterable = true;
+	amroutine->ampredlocks = false;
+	amroutine->amkeytype = InvalidOid;
+
+	amroutine->ambuild = gistbuild;
+	amroutine->ambuildempty = gistbuildempty;
+	amroutine->aminsert = gistinsert;
+	amroutine->ambulkdelete = gistbulkdelete;
+	amroutine->amvacuumcleanup = gistvacuumcleanup;
+	amroutine->amcanreturn = gistcanreturn;
+	amroutine->amcostestimate = gistcostestimate;
+	amroutine->amoptions = gistoptions;
+	amroutine->amvalidate = gistvalidate;
+	amroutine->ambeginscan = gistbeginscan;
+	amroutine->amrescan = gistrescan;
+	amroutine->amgettuple = gistgettuple;
+	amroutine->amgetbitmap = gistgetbitmap;
+	amroutine->amendscan = gistendscan;
+	amroutine->ammarkpos = NULL;
+	amroutine->amrestrpos = NULL;
+
+	PG_RETURN_POINTER(amroutine);
+}
+
+/*
  * Create and return a temporary memory context for use by GiST. We
  * _always_ invoke user-provided methods in a temporary memory
  * context, so that memory leaks in those functions cannot cause
@@ -70,10 +112,9 @@ createTempGistContext(void)
 /*
  *	gistbuildempty() -- build an empty gist index in the initialization fork
  */
-Datum
-gistbuildempty(PG_FUNCTION_ARGS)
+void
+gistbuildempty(Relation index)
 {
-	Relation	index = (Relation) PG_GETARG_POINTER(0);
 	Buffer		buffer;
 
 	/* Initialize the root page */
@@ -89,8 +130,6 @@ gistbuildempty(PG_FUNCTION_ARGS)
 
 	/* Unlock and release the buffer */
 	UnlockReleaseBuffer(buffer);
-
-	PG_RETURN_VOID();
 }
 
 /*
@@ -99,18 +138,11 @@ gistbuildempty(PG_FUNCTION_ARGS)
  *	  This is the public interface routine for tuple insertion in GiSTs.
  *	  It doesn't do any work; just locks the relation and passes the buck.
  */
-Datum
-gistinsert(PG_FUNCTION_ARGS)
+bool
+gistinsert(Relation r, Datum *values, bool *isnull,
+		   ItemPointer ht_ctid, Relation heapRel,
+		   IndexUniqueCheck checkUnique)
 {
-	Relation	r = (Relation) PG_GETARG_POINTER(0);
-	Datum	   *values = (Datum *) PG_GETARG_POINTER(1);
-	bool	   *isnull = (bool *) PG_GETARG_POINTER(2);
-	ItemPointer ht_ctid = (ItemPointer) PG_GETARG_POINTER(3);
-
-#ifdef NOT_USED
-	Relation	heapRel = (Relation) PG_GETARG_POINTER(4);
-	IndexUniqueCheck checkUnique = (IndexUniqueCheck) PG_GETARG_INT32(5);
-#endif
 	IndexTuple	itup;
 	GISTSTATE  *giststate;
 	MemoryContext oldCxt;
@@ -136,7 +168,7 @@ gistinsert(PG_FUNCTION_ARGS)
 	MemoryContextSwitchTo(oldCxt);
 	freeGISTstate(giststate);
 
-	PG_RETURN_BOOL(false);
+	return false;
 }
 
 
diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c
index 98ea0cb2d14..4e43a6932a4 100644
--- a/src/backend/access/gist/gistbuild.c
+++ b/src/backend/access/gist/gistbuild.c
@@ -109,12 +109,9 @@ static BlockNumber gistGetParent(GISTBuildState *buildstate, BlockNumber child);
  * but switches to more efficient buffering build algorithm after a certain
  * number of tuples (unless buffering mode is disabled).
  */
-Datum
-gistbuild(PG_FUNCTION_ARGS)
+IndexBuildResult *
+gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 {
-	Relation	heap = (Relation) PG_GETARG_POINTER(0);
-	Relation	index = (Relation) PG_GETARG_POINTER(1);
-	IndexInfo  *indexInfo = (IndexInfo *) PG_GETARG_POINTER(2);
 	IndexBuildResult *result;
 	double		reltuples;
 	GISTBuildState buildstate;
@@ -232,7 +229,7 @@ gistbuild(PG_FUNCTION_ARGS)
 	result->heap_tuples = reltuples;
 	result->index_tuples = (double) buildstate.indtuples;
 
-	PG_RETURN_POINTER(result);
+	return result;
 }
 
 /*
diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index 21f9de511ff..41b83431b61 100644
--- a/src/backend/access/gist/gistget.c
+++ b/src/backend/access/gist/gistget.c
@@ -618,18 +618,16 @@ getNextNearest(IndexScanDesc scan)
 /*
  * gistgettuple() -- Get the next tuple in the scan
  */
-Datum
-gistgettuple(PG_FUNCTION_ARGS)
+bool
+gistgettuple(IndexScanDesc scan, ScanDirection dir)
 {
-	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
-	ScanDirection dir = (ScanDirection) PG_GETARG_INT32(1);
 	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
 
 	if (dir != ForwardScanDirection)
 		elog(ERROR, "GiST only supports forward scan direction");
 
 	if (!so->qual_ok)
-		PG_RETURN_BOOL(false);
+		return false;
 
 	if (so->firstCall)
 	{
@@ -651,7 +649,7 @@ gistgettuple(PG_FUNCTION_ARGS)
 	if (scan->numberOfOrderBys > 0)
 	{
 		/* Must fetch tuples in strict distance order */
-		PG_RETURN_BOOL(getNextNearest(scan));
+		return getNextNearest(scan);
 	}
 	else
 	{
@@ -688,7 +686,7 @@ gistgettuple(PG_FUNCTION_ARGS)
 
 				so->curPageData++;
 
-				PG_RETURN_BOOL(true);
+				return true;
 			}
 
 			/*
@@ -726,7 +724,7 @@ gistgettuple(PG_FUNCTION_ARGS)
 				item = getNextGISTSearchItem(so);
 
 				if (!item)
-					PG_RETURN_BOOL(false);
+					return false;
 
 				CHECK_FOR_INTERRUPTS();
 
@@ -750,17 +748,15 @@ gistgettuple(PG_FUNCTION_ARGS)
 /*
  * gistgetbitmap() -- Get a bitmap of all heap tuple locations
  */
-Datum
-gistgetbitmap(PG_FUNCTION_ARGS)
+int64
+gistgetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
 {
-	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
-	TIDBitmap  *tbm = (TIDBitmap *) PG_GETARG_POINTER(1);
 	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
 	int64		ntids = 0;
 	GISTSearchItem fakeItem;
 
 	if (!so->qual_ok)
-		PG_RETURN_INT64(0);
+		return 0;
 
 	pgstat_count_index_scan(scan->indexRelation);
 
@@ -791,7 +787,7 @@ gistgetbitmap(PG_FUNCTION_ARGS)
 		pfree(item);
 	}
 
-	PG_RETURN_INT64(ntids);
+	return ntids;
 }
 
 /*
@@ -799,14 +795,11 @@ gistgetbitmap(PG_FUNCTION_ARGS)
  *
  * Opclasses that implement a fetch function support index-only scans.
  */
-Datum
-gistcanreturn(PG_FUNCTION_ARGS)
+bool
+gistcanreturn(Relation index, int attno)
 {
-	Relation	index = (Relation) PG_GETARG_POINTER(0);
-	int			attno = PG_GETARG_INT32(1);
-
 	if (OidIsValid(index_getprocid(index, attno, GIST_FETCH_PROC)))
-		PG_RETURN_BOOL(true);
+		return true;
 	else
-		PG_RETURN_BOOL(false);
+		return false;
 }
diff --git a/src/backend/access/gist/gistscan.c b/src/backend/access/gist/gistscan.c
index 8ab41838361..31758a1c8fe 100644
--- a/src/backend/access/gist/gistscan.c
+++ b/src/backend/access/gist/gistscan.c
@@ -54,12 +54,9 @@ pairingheap_GISTSearchItem_cmp(const pairingheap_node *a, const pairingheap_node
  * Index AM API functions for scanning GiST indexes
  */
 
-Datum
-gistbeginscan(PG_FUNCTION_ARGS)
+IndexScanDesc
+gistbeginscan(Relation r, int nkeys, int norderbys)
 {
-	Relation	r = (Relation) PG_GETARG_POINTER(0);
-	int			nkeys = PG_GETARG_INT32(1);
-	int			norderbys = PG_GETARG_INT32(2);
 	IndexScanDesc scan;
 	GISTSTATE  *giststate;
 	GISTScanOpaque so;
@@ -107,16 +104,13 @@ gistbeginscan(PG_FUNCTION_ARGS)
 
 	MemoryContextSwitchTo(oldCxt);
 
-	PG_RETURN_POINTER(scan);
+	return scan;
 }
 
-Datum
-gistrescan(PG_FUNCTION_ARGS)
+void
+gistrescan(IndexScanDesc scan, ScanKey key, int nkeys,
+		   ScanKey orderbys, int norderbys)
 {
-	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
-	ScanKey		key = (ScanKey) PG_GETARG_POINTER(1);
-	ScanKey		orderbys = (ScanKey) PG_GETARG_POINTER(3);
-
 	/* nkeys and norderbys arguments are ignored */
 	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
 	bool		first_time;
@@ -314,28 +308,11 @@ gistrescan(PG_FUNCTION_ARGS)
 		if (!first_time)
 			pfree(fn_extras);
 	}
-
-	PG_RETURN_VOID();
-}
-
-Datum
-gistmarkpos(PG_FUNCTION_ARGS)
-{
-	elog(ERROR, "GiST does not support mark/restore");
-	PG_RETURN_VOID();
 }
 
-Datum
-gistrestrpos(PG_FUNCTION_ARGS)
+void
+gistendscan(IndexScanDesc scan)
 {
-	elog(ERROR, "GiST does not support mark/restore");
-	PG_RETURN_VOID();
-}
-
-Datum
-gistendscan(PG_FUNCTION_ARGS)
-{
-	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
 	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
 
 	/*
@@ -343,6 +320,4 @@ gistendscan(PG_FUNCTION_ARGS)
 	 * as well as the queueCxt if there is a separate context for it.
 	 */
 	freeGISTstate(so->giststate);
-
-	PG_RETURN_VOID();
 }
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index 0995e0355cf..fac166d4c29 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -808,11 +808,9 @@ gistNewBuffer(Relation r)
 	return buffer;
 }
 
-Datum
-gistoptions(PG_FUNCTION_ARGS)
+bytea *
+gistoptions(Datum reloptions, bool validate)
 {
-	Datum		reloptions = PG_GETARG_DATUM(0);
-	bool		validate = PG_GETARG_BOOL(1);
 	relopt_value *options;
 	GiSTOptions *rdopts;
 	int			numoptions;
@@ -826,7 +824,7 @@ gistoptions(PG_FUNCTION_ARGS)
 
 	/* if none set, we're done */
 	if (numoptions == 0)
-		PG_RETURN_NULL();
+		return NULL;
 
 	rdopts = allocateReloptStruct(sizeof(GiSTOptions), options, numoptions);
 
@@ -835,8 +833,7 @@ gistoptions(PG_FUNCTION_ARGS)
 
 	pfree(options);
 
-	PG_RETURN_BYTEA_P(rdopts);
-
+	return (bytea *) rdopts;
 }
 
 /*
diff --git a/src/backend/access/gist/gistvacuum.c b/src/backend/access/gist/gistvacuum.c
index 346f6d96f4d..7947ff9dbe6 100644
--- a/src/backend/access/gist/gistvacuum.c
+++ b/src/backend/access/gist/gistvacuum.c
@@ -25,11 +25,9 @@
 /*
  * VACUUM cleanup: update FSM
  */
-Datum
-gistvacuumcleanup(PG_FUNCTION_ARGS)
+IndexBulkDeleteResult *
+gistvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
 {
-	IndexVacuumInfo *info = (IndexVacuumInfo *) PG_GETARG_POINTER(0);
-	IndexBulkDeleteResult *stats = (IndexBulkDeleteResult *) PG_GETARG_POINTER(1);
 	Relation	rel = info->index;
 	BlockNumber npages,
 				blkno;
@@ -38,7 +36,7 @@ gistvacuumcleanup(PG_FUNCTION_ARGS)
 
 	/* No-op in ANALYZE ONLY mode */
 	if (info->analyze_only)
-		PG_RETURN_POINTER(stats);
+		return stats;
 
 	/* Set up all-zero stats if gistbulkdelete wasn't called */
 	if (stats == NULL)
@@ -98,7 +96,7 @@ gistvacuumcleanup(PG_FUNCTION_ARGS)
 	if (needLock)
 		UnlockRelationForExtension(rel, ExclusiveLock);
 
-	PG_RETURN_POINTER(stats);
+	return stats;
 }
 
 typedef struct GistBDItem
@@ -137,13 +135,10 @@ pushStackIfSplited(Page page, GistBDItem *stack)
  *
  * Result: a palloc'd struct containing statistical info for VACUUM displays.
  */
-Datum
-gistbulkdelete(PG_FUNCTION_ARGS)
+IndexBulkDeleteResult *
+gistbulkdelete(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
+			   IndexBulkDeleteCallback callback, void *callback_state)
 {
-	IndexVacuumInfo *info = (IndexVacuumInfo *) PG_GETARG_POINTER(0);
-	IndexBulkDeleteResult *stats = (IndexBulkDeleteResult *) PG_GETARG_POINTER(1);
-	IndexBulkDeleteCallback callback = (IndexBulkDeleteCallback) PG_GETARG_POINTER(2);
-	void	   *callback_state = (void *) PG_GETARG_POINTER(3);
 	Relation	rel = info->index;
 	GistBDItem *stack,
 			   *ptr;
@@ -276,5 +271,5 @@ gistbulkdelete(PG_FUNCTION_ARGS)
 		vacuum_delay_point();
 	}
 
-	PG_RETURN_POINTER(stats);
+	return stats;
 }
diff --git a/src/backend/access/gist/gistvalidate.c b/src/backend/access/gist/gistvalidate.c
new file mode 100644
index 00000000000..86b5aeaec5c
--- /dev/null
+++ b/src/backend/access/gist/gistvalidate.c
@@ -0,0 +1,133 @@
+/*-------------------------------------------------------------------------
+ *
+ * gistvalidate.c
+ *	  Opclass validator for GiST.
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/gist/gistvalidate.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/gist_private.h"
+#include "access/htup_details.h"
+#include "catalog/pg_amop.h"
+#include "catalog/pg_amproc.h"
+#include "catalog/pg_opclass.h"
+#include "utils/catcache.h"
+#include "utils/syscache.h"
+
+
+/*
+ * Validator for a GiST opclass.
+ */
+bool
+gistvalidate(Oid opclassoid)
+{
+	HeapTuple	classtup;
+	Form_pg_opclass classform;
+	Oid			opfamilyoid;
+	Oid			opcintype;
+	int			numclassops;
+	int32		classfuncbits;
+	CatCList   *proclist,
+			   *oprlist;
+	int			i;
+
+	/* Fetch opclass information */
+	classtup = SearchSysCache1(CLAOID, ObjectIdGetDatum(opclassoid));
+	if (!HeapTupleIsValid(classtup))
+		elog(ERROR, "cache lookup failed for operator class %u", opclassoid);
+	classform = (Form_pg_opclass) GETSTRUCT(classtup);
+
+	opfamilyoid = classform->opcfamily;
+	opcintype = classform->opcintype;
+
+	ReleaseSysCache(classtup);
+
+	/* Fetch all operators and support functions of the opfamily */
+	oprlist = SearchSysCacheList1(AMOPSTRATEGY, ObjectIdGetDatum(opfamilyoid));
+	proclist = SearchSysCacheList1(AMPROCNUM, ObjectIdGetDatum(opfamilyoid));
+
+	/* We'll track the ops and functions belonging to the named opclass */
+	numclassops = 0;
+	classfuncbits = 0;
+
+	/* Check support functions */
+	for (i = 0; i < proclist->n_members; i++)
+	{
+		HeapTuple	proctup = &proclist->members[i]->tuple;
+		Form_pg_amproc procform = (Form_pg_amproc) GETSTRUCT(proctup);
+
+		/* Check that only allowed procedure numbers exist */
+		if (procform->amprocnum < 1 ||
+			procform->amprocnum > GISTNProcs)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("gist opfamily %u contains invalid support number %d for procedure %u",
+							opfamilyoid,
+							procform->amprocnum, procform->amproc)));
+
+		/* Remember functions that are specifically for the named opclass */
+		if (procform->amproclefttype == opcintype &&
+			procform->amprocrighttype == opcintype)
+			classfuncbits |= (1 << procform->amprocnum);
+	}
+
+	/* Check operators */
+	for (i = 0; i < oprlist->n_members; i++)
+	{
+		HeapTuple	oprtup = &oprlist->members[i]->tuple;
+		Form_pg_amop oprform = (Form_pg_amop) GETSTRUCT(oprtup);
+
+		/* TODO: Check that only allowed strategy numbers exist */
+		if (oprform->amopstrategy < 1)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("gist opfamily %u contains invalid strategy number %d for operator %u",
+							opfamilyoid,
+							oprform->amopstrategy, oprform->amopopr)));
+
+		/* GiST supports ORDER BY operators, but must have distance proc */
+		if (oprform->amoppurpose != AMOP_SEARCH &&
+			oprform->amoplefttype == opcintype &&
+			oprform->amoprighttype == opcintype &&
+			(classfuncbits & (1 << GIST_DISTANCE_PROC)) == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("gist opfamily %u contains unsupported ORDER BY specification for operator %u",
+							opfamilyoid, oprform->amopopr)));
+
+		/* Count operators that are specifically for the named opclass */
+		/* XXX we consider only lefttype here */
+		if (oprform->amoplefttype == opcintype)
+			numclassops++;
+	}
+
+	/* Check that the named opclass is complete */
+	if (numclassops == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("gist opclass %u is missing operator(s)",
+						opclassoid)));
+	for (i = 1; i <= GISTNProcs; i++)
+	{
+		if ((classfuncbits & (1 << i)) != 0)
+			continue;			/* got it */
+		if (i == GIST_DISTANCE_PROC || i == GIST_FETCH_PROC)
+			continue;			/* optional methods */
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+			errmsg("gist opclass %u is missing required support function %d",
+				   opclassoid, i)));
+	}
+
+	ReleaseCatCacheList(proclist);
+	ReleaseCatCacheList(oprlist);
+
+	return true;
+}