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.

src/backend/access/gin/Makefile

@@ -14,6 +14,6 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = ginutil.o gininsert.o ginxlog.o ginentrypage.o gindatapage.o \
 	ginbtree.o ginscan.o ginget.o ginvacuum.o ginarrayproc.o \
-	ginbulk.o ginfast.o ginpostinglist.o ginlogic.o
+	ginbulk.o ginfast.o ginpostinglist.o ginlogic.o ginvalidate.o
 
 include $(top_srcdir)/src/backend/common.mk

src/backend/access/gin/ginget.c

@@ -1772,11 +1772,9 @@ scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
 
 #define GinIsVoidRes(s)		( ((GinScanOpaque) scan->opaque)->isVoidRes )
 
-Datum
-gingetbitmap(PG_FUNCTION_ARGS)
+int64
+gingetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
 {
-	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
-	TIDBitmap  *tbm = (TIDBitmap *) PG_GETARG_POINTER(1);
 	GinScanOpaque so = (GinScanOpaque) scan->opaque;
 	int64		ntids;
 	ItemPointerData iptr;
@@ -1790,7 +1788,7 @@ gingetbitmap(PG_FUNCTION_ARGS)
 	ginNewScanKey(scan);
 
 	if (GinIsVoidRes(scan))
-		PG_RETURN_INT64(0);
+		return 0;
 
 	ntids = 0;
 
@@ -1827,5 +1825,5 @@ gingetbitmap(PG_FUNCTION_ARGS)
 		ntids++;
 	}
 
-	PG_RETURN_INT64(ntids);
+	return ntids;
 }

src/backend/access/gin/gininsert.c

@@ -306,12 +306,9 @@ ginBuildCallback(Relation index, HeapTuple htup, Datum *values,
 	MemoryContextSwitchTo(oldCtx);
 }
 
-Datum
-ginbuild(PG_FUNCTION_ARGS)
+IndexBuildResult *
+ginbuild(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;
 	GinBuildState buildstate;
@@ -429,16 +426,15 @@ ginbuild(PG_FUNCTION_ARGS)
 	result->heap_tuples = reltuples;
 	result->index_tuples = buildstate.indtuples;
 
-	PG_RETURN_POINTER(result);
+	return result;
 }
 
 /*
  *	ginbuildempty() -- build an empty gin index in the initialization fork
  */
-Datum
-ginbuildempty(PG_FUNCTION_ARGS)
+void
+ginbuildempty(Relation index)
 {
-	Relation	index = (Relation) PG_GETARG_POINTER(0);
 	Buffer		RootBuffer,
 				MetaBuffer;
 
@@ -463,8 +459,6 @@ ginbuildempty(PG_FUNCTION_ARGS)
 	/* Unlock and release the buffers. */
 	UnlockReleaseBuffer(MetaBuffer);
 	UnlockReleaseBuffer(RootBuffer);
-
-	PG_RETURN_VOID();
 }
 
 /*
@@ -489,18 +483,11 @@ ginHeapTupleInsert(GinState *ginstate, OffsetNumber attnum,
 					   item, 1, NULL);
 }
 
-Datum
-gininsert(PG_FUNCTION_ARGS)
+bool
+gininsert(Relation index, Datum *values, bool *isnull,
+		  ItemPointer ht_ctid, Relation heapRel,
+		  IndexUniqueCheck checkUnique)
 {
-	Relation	index = (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
 	GinState	ginstate;
 	MemoryContext oldCtx;
 	MemoryContext insertCtx;
@@ -541,5 +528,5 @@ gininsert(PG_FUNCTION_ARGS)
 	MemoryContextSwitchTo(oldCtx);
 	MemoryContextDelete(insertCtx);
 
-	PG_RETURN_BOOL(false);
+	return false;
 }

src/backend/access/gin/ginscan.c

@@ -21,12 +21,9 @@
 #include "utils/rel.h"
 
 
-Datum
-ginbeginscan(PG_FUNCTION_ARGS)
+IndexScanDesc
+ginbeginscan(Relation rel, int nkeys, int norderbys)
 {
-	Relation	rel = (Relation) PG_GETARG_POINTER(0);
-	int			nkeys = PG_GETARG_INT32(1);
-	int			norderbys = PG_GETARG_INT32(2);
 	IndexScanDesc scan;
 	GinScanOpaque so;
 
@@ -53,7 +50,7 @@ ginbeginscan(PG_FUNCTION_ARGS)
 
 	scan->opaque = so;
 
-	PG_RETURN_POINTER(scan);
+	return scan;
 }
 
 /*
@@ -417,13 +414,10 @@ ginNewScanKey(IndexScanDesc scan)
 	pgstat_count_index_scan(scan->indexRelation);
 }
 
-Datum
-ginrescan(PG_FUNCTION_ARGS)
+void
+ginrescan(IndexScanDesc scan, ScanKey scankey, int nscankeys,
+		  ScanKey orderbys, int norderbys)
 {
-	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
-	ScanKey		scankey = (ScanKey) PG_GETARG_POINTER(1);
-
-	/* remaining arguments are ignored */
 	GinScanOpaque so = (GinScanOpaque) scan->opaque;
 
 	ginFreeScanKeys(so);
@@ -433,15 +427,12 @@ ginrescan(PG_FUNCTION_ARGS)
 		memmove(scan->keyData, scankey,
 				scan->numberOfKeys * sizeof(ScanKeyData));
 	}
-
-	PG_RETURN_VOID();
 }
 
 
-Datum
-ginendscan(PG_FUNCTION_ARGS)
+void
+ginendscan(IndexScanDesc scan)
 {
-	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
 	GinScanOpaque so = (GinScanOpaque) scan->opaque;
 
 	ginFreeScanKeys(so);
@@ -450,20 +441,4 @@ ginendscan(PG_FUNCTION_ARGS)
 	MemoryContextDelete(so->keyCtx);
 
 	pfree(so);
-
-	PG_RETURN_VOID();
-}
-
-Datum
-ginmarkpos(PG_FUNCTION_ARGS)
-{
-	elog(ERROR, "GIN does not support mark/restore");
-	PG_RETURN_VOID();
-}
-
-Datum
-ginrestrpos(PG_FUNCTION_ARGS)
-{
-	elog(ERROR, "GIN does not support mark/restore");
-	PG_RETURN_VOID();
 }

src/backend/access/gin/ginutil.c

@@ -1,7 +1,7 @@
 /*-------------------------------------------------------------------------
  *
  * ginutil.c
- *	  utilities routines for the postgres inverted index access method.
+ *	  Utility routines for the Postgres inverted index access method.
  *
  *
  * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
@@ -22,8 +22,53 @@
 #include "miscadmin.h"
 #include "storage/indexfsm.h"
 #include "storage/lmgr.h"
+#include "utils/index_selfuncs.h"
 
 
+/*
+ * GIN handler function: return IndexAmRoutine with access method parameters
+ * and callbacks.
+ */
+Datum
+ginhandler(PG_FUNCTION_ARGS)
+{
+	IndexAmRoutine *amroutine = makeNode(IndexAmRoutine);
+
+	amroutine->amstrategies = 0;
+	amroutine->amsupport = 6;
+	amroutine->amcanorder = false;
+	amroutine->amcanorderbyop = false;
+	amroutine->amcanbackward = false;
+	amroutine->amcanunique = false;
+	amroutine->amcanmulticol = true;
+	amroutine->amoptionalkey = true;
+	amroutine->amsearcharray = false;
+	amroutine->amsearchnulls = false;
+	amroutine->amstorage = true;
+	amroutine->amclusterable = false;
+	amroutine->ampredlocks = false;
+	amroutine->amkeytype = InvalidOid;
+
+	amroutine->ambuild = ginbuild;
+	amroutine->ambuildempty = ginbuildempty;
+	amroutine->aminsert = gininsert;
+	amroutine->ambulkdelete = ginbulkdelete;
+	amroutine->amvacuumcleanup = ginvacuumcleanup;
+	amroutine->amcanreturn = NULL;
+	amroutine->amcostestimate = gincostestimate;
+	amroutine->amoptions = ginoptions;
+	amroutine->amvalidate = ginvalidate;
+	amroutine->ambeginscan = ginbeginscan;
+	amroutine->amrescan = ginrescan;
+	amroutine->amgettuple = NULL;
+	amroutine->amgetbitmap = gingetbitmap;
+	amroutine->amendscan = ginendscan;
+	amroutine->ammarkpos = NULL;
+	amroutine->amrestrpos = NULL;
+
+	PG_RETURN_POINTER(amroutine);
+}
+
 /*
  * initGinState: fill in an empty GinState struct to describe the index
  *
@@ -516,11 +561,9 @@ ginExtractEntries(GinState *ginstate, OffsetNumber attnum,
 	return entries;
 }
 
-Datum
-ginoptions(PG_FUNCTION_ARGS)
+bytea *
+ginoptions(Datum reloptions, bool validate)
 {
-	Datum		reloptions = PG_GETARG_DATUM(0);
-	bool		validate = PG_GETARG_BOOL(1);
 	relopt_value *options;
 	GinOptions *rdopts;
 	int			numoptions;
@@ -535,7 +578,7 @@ ginoptions(PG_FUNCTION_ARGS)
 
 	/* if none set, we're done */
 	if (numoptions == 0)
-		PG_RETURN_NULL();
+		return NULL;
 
 	rdopts = allocateReloptStruct(sizeof(GinOptions), options, numoptions);
 
@@ -544,7 +587,7 @@ ginoptions(PG_FUNCTION_ARGS)
 
 	pfree(options);
 
-	PG_RETURN_BYTEA_P(rdopts);
+	return (bytea *) rdopts;
 }
 
 /*

src/backend/access/gin/ginvacuum.c

@@ -513,13 +513,10 @@ ginVacuumEntryPage(GinVacuumState *gvs, Buffer buffer, BlockNumber *roots, uint3
 	return (tmppage == origpage) ? NULL : tmppage;
 }
 
-Datum
-ginbulkdelete(PG_FUNCTION_ARGS)
+IndexBulkDeleteResult *
+ginbulkdelete(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	index = info->index;
 	BlockNumber blkno = GIN_ROOT_BLKNO;
 	GinVacuumState gvs;
@@ -634,14 +631,12 @@ ginbulkdelete(PG_FUNCTION_ARGS)
 
 	MemoryContextDelete(gvs.tmpCxt);
 
-	PG_RETURN_POINTER(gvs.result);
+	return gvs.result;
 }
 
-Datum
-ginvacuumcleanup(PG_FUNCTION_ARGS)
+IndexBulkDeleteResult *
+ginvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
 {
-	IndexVacuumInfo *info = (IndexVacuumInfo *) PG_GETARG_POINTER(0);
-	IndexBulkDeleteResult *stats = (IndexBulkDeleteResult *) PG_GETARG_POINTER(1);
 	Relation	index = info->index;
 	bool		needLock;
 	BlockNumber npages,
@@ -661,7 +656,7 @@ ginvacuumcleanup(PG_FUNCTION_ARGS)
 			initGinState(&ginstate, index);
 			ginInsertCleanup(&ginstate, true, true, stats);
 		}
-		PG_RETURN_POINTER(stats);
+		return stats;
 	}
 
 	/*
@@ -746,5 +741,5 @@ ginvacuumcleanup(PG_FUNCTION_ARGS)
 	if (needLock)
 		UnlockRelationForExtension(index, ExclusiveLock);
 
-	PG_RETURN_POINTER(stats);
+	return stats;
 }

src/backend/access/gin/ginvalidate.c

@@ -0,0 +1,145 @@
+/*-------------------------------------------------------------------------
+ *
+ * ginvalidate.c
+ *	  Opclass validator for GIN.
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *			src/backend/access/gin/ginvalidate.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/gin_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 GIN opclass.
+ */
+bool
+ginvalidate(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 > GINNProcs)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("gin 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("gin opfamily %u contains invalid strategy number %d for operator %u",
+							opfamilyoid,
+							oprform->amopstrategy, oprform->amopopr)));
+
+		/* gin doesn't support ORDER BY operators */
+		if (oprform->amoppurpose != AMOP_SEARCH ||
+			OidIsValid(oprform->amopsortfamily))
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("gin opfamily %u contains invalid ORDER BY specification for operator %u",
+							opfamilyoid, oprform->amopopr)));
+
+		/* Count operators that are specifically for the named opclass */
+		if (oprform->amoplefttype == opcintype &&
+			oprform->amoprighttype == opcintype)
+			numclassops++;
+	}
+
+	/* Check that the named opclass is complete */
+
+	/* XXX needs work: we need to detect applicability of ANYARRAY operators */
+#ifdef NOT_USED
+	if (numclassops == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("gin opclass %u is missing operator(s)",
+						opclassoid)));
+#endif
+
+	for (i = 1; i <= GINNProcs; i++)
+	{
+		if ((classfuncbits & (1 << i)) != 0)
+			continue;			/* got it */
+		if (i == GIN_COMPARE_PARTIAL_PROC)
+			continue;			/* optional method */
+		if (i == GIN_CONSISTENT_PROC || i == GIN_TRICONSISTENT_PROC)
+			continue;			/* don't need to have both, see check below
+								 * loop */
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+			 errmsg("gin opclass %u is missing required support function %d",
+					opclassoid, i)));
+	}
+	if ((classfuncbits & (1 << GIN_CONSISTENT_PROC)) == 0 &&
+		(classfuncbits & (1 << GIN_TRICONSISTENT_PROC)) == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("gin opclass %u is missing required support function",
+						opclassoid)));
+
+	ReleaseCatCacheList(proclist);
+	ReleaseCatCacheList(oprlist);
+
+	return true;
+}