IndexAM: Add amreuse

Author: e-ivkov

contrib/bloom/blutils.c

@@ -129,6 +129,7 @@ blhandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = blbuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = blbuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = blinsert;

src/backend/access/brin/brin.c

@@ -115,6 +115,7 @@ brinhandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = brinbuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = brinbuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = brininsert;

src/backend/access/gin/ginutil.c

@@ -62,6 +62,7 @@ ginhandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = ginbuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = ginbuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = gininsert;

src/backend/access/gist/gist.c

@@ -84,6 +84,7 @@ gisthandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = gistbuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = gistbuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = gistinsert;

src/backend/access/hash/hash.c

@@ -81,6 +81,7 @@ hashhandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = INT4OID;
 
 	amroutine->ambuild = hashbuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = hashbuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = hashinsert;

src/backend/access/nbtree/nbtree.c

@@ -120,6 +120,7 @@ bthandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = btbuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = btbuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = btinsert;

src/backend/access/spgist/spgutils.c

@@ -68,6 +68,7 @@ spghandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = spgbuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = spgbuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = spginsert;

src/backend/commands/tablecmds.c

@@ -92,6 +92,7 @@
 #include "tcop/utility.h"
 #include "utils/acl.h"
 #include "utils/builtins.h"
+#include "utils/elog.h"
 #include "utils/fmgroids.h"
 #include "utils/inval.h"
 #include "utils/lsyscache.h"
@@ -13942,9 +13943,50 @@ TryReuseIndex(Oid oldId, IndexStmt *stmt)
 		/* If it's a partitioned index, there is no storage to share. */
 		if (irel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
 		{
+			HeapTuple	tuple;
+			Form_pg_am	accessMethodForm;
+			IndexAmRoutine *amRoutine;
+			char	   *accessMethodName;
+			Oid heapRelId = IndexGetRelation(oldId, false);
+			Relation heapRel = table_open(heapRelId, ShareLock);
+			
 			stmt->oldNumber = irel->rd_locator.relNumber;
 			stmt->oldCreateSubid = irel->rd_createSubid;
 			stmt->oldFirstRelfilelocatorSubid = irel->rd_firstRelfilelocatorSubid;
+			
+			
+			/*
+			 * look up the access method to call amreuse
+			 */
+			accessMethodName = stmt->accessMethod;
+			tuple = SearchSysCache1(AMNAME, PointerGetDatum(accessMethodName));
+			if (!HeapTupleIsValid(tuple))
+			{
+				/*
+				 * Hack to provide more-or-less-transparent updating of old RTREE
+				 * indexes to GiST: if RTREE is requested and not found, use GIST.
+				 */
+				if (strcmp(accessMethodName, "rtree") == 0)
+				{
+					ereport(NOTICE,
+							(errmsg("substituting access method \"gist\" for obsolete method \"rtree\"")));
+					accessMethodName = "gist";
+					tuple = SearchSysCache1(AMNAME, PointerGetDatum(accessMethodName));
+				}
+
+				if (!HeapTupleIsValid(tuple))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_OBJECT),
+							 errmsg("access method \"%s\" does not exist",
+									accessMethodName)));
+			}
+			accessMethodForm = (Form_pg_am) GETSTRUCT(tuple);
+			amRoutine = GetIndexAmRoutineWithTableAM(heapRel->rd_rel->relam, accessMethodForm->amhandler);
+			table_close(heapRel, NoLock);
+			
+			if(amRoutine->amreuse) {
+				(*amRoutine->amreuse)(irel);
+			}
 		}
 		index_close(irel, NoLock);
 	}

src/include/access/amapi.h

@@ -104,6 +104,9 @@ typedef IndexBuildResult *(*ambuild_function) (Relation heapRelation,
 											   Relation indexRelation,
 											   struct IndexInfo *indexInfo);
 
+/* reuse current index - don't drop it */
+typedef void (*amreuse_function) (Relation indexRelation);
+
 /* build empty index */
 typedef void (*ambuildempty_function) (Relation indexRelation);
 
@@ -295,6 +298,7 @@ typedef struct IndexAmRoutine
 
 	/* interface functions */
 	ambuild_function ambuild;
+	amreuse_function amreuse;
 	ambuildempty_function ambuildempty;
 	aminsert_function aminsert;
 	aminsert_extended_function aminsertextended;

src/test/modules/dummy_index_am/dummy_index_am.c

@@ -301,6 +301,7 @@ dihandler(PG_FUNCTION_ARGS)
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = dibuild;
+	amroutine->amreuse = NULL;
 	amroutine->ambuildempty = dibuildempty;
 	amroutine->aminsert = NULL;
 	amroutine->aminsertextended = diinsert;