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.

1 files changed, 21 insertions, 9 deletions

diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 71f4b5ef633..f9732ba7fb9 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -14,6 +14,7 @@
 #ifndef GIST_PRIVATE_H
 #define GIST_PRIVATE_H
 
+#include "access/amapi.h"
 #include "access/gist.h"
 #include "access/itup.h"
 #include "access/xlogreader.h"
@@ -426,9 +427,11 @@ typedef struct GiSTOptions
 } GiSTOptions;
 
 /* gist.c */
-extern Datum gistbuildempty(PG_FUNCTION_ARGS);
-extern Datum gistinsert(PG_FUNCTION_ARGS);
-extern Datum gistcanreturn(PG_FUNCTION_ARGS);
+extern Datum gisthandler(PG_FUNCTION_ARGS);
+extern void gistbuildempty(Relation index);
+extern bool gistinsert(Relation r, Datum *values, bool *isnull,
+		   ItemPointer ht_ctid, Relation heapRel,
+		   IndexUniqueCheck checkUnique);
 extern MemoryContext createTempGistContext(void);
 extern GISTSTATE *initGISTstate(Relation index);
 extern void freeGISTstate(GISTSTATE *giststate);
@@ -474,8 +477,12 @@ extern XLogRecPtr gistXLogSplit(RelFileNode node,
 			  Buffer leftchild, bool markfollowright);
 
 /* gistget.c */
-extern Datum gistgettuple(PG_FUNCTION_ARGS);
-extern Datum gistgetbitmap(PG_FUNCTION_ARGS);
+extern bool gistgettuple(IndexScanDesc scan, ScanDirection dir);
+extern int64 gistgetbitmap(IndexScanDesc scan, TIDBitmap *tbm);
+extern bool gistcanreturn(Relation index, int attno);
+
+/* gistvalidate.c */
+extern bool gistvalidate(Oid opclassoid);
 
 /* gistutil.c */
 
@@ -485,7 +492,7 @@ extern Datum gistgetbitmap(PG_FUNCTION_ARGS);
 #define GIST_MIN_FILLFACTOR			10
 #define GIST_DEFAULT_FILLFACTOR		90
 
-extern Datum gistoptions(PG_FUNCTION_ARGS);
+extern bytea *gistoptions(Datum reloptions, bool validate);
 extern bool gistfitpage(IndexTuple *itvec, int len);
 extern bool gistnospace(Page page, IndexTuple *itvec, int len, OffsetNumber todelete, Size freespace);
 extern void gistcheckpage(Relation rel, Buffer buf);
@@ -534,8 +541,12 @@ extern void gistMakeUnionKey(GISTSTATE *giststate, int attno,
 extern XLogRecPtr gistGetFakeLSN(Relation rel);
 
 /* gistvacuum.c */
-extern Datum gistbulkdelete(PG_FUNCTION_ARGS);
-extern Datum gistvacuumcleanup(PG_FUNCTION_ARGS);
+extern IndexBulkDeleteResult *gistbulkdelete(IndexVacuumInfo *info,
+			   IndexBulkDeleteResult *stats,
+			   IndexBulkDeleteCallback callback,
+			   void *callback_state);
+extern IndexBulkDeleteResult *gistvacuumcleanup(IndexVacuumInfo *info,
+				  IndexBulkDeleteResult *stats);
 
 /* gistsplit.c */
 extern void gistSplitByKey(Relation r, Page page, IndexTuple *itup,
@@ -544,7 +555,8 @@ extern void gistSplitByKey(Relation r, Page page, IndexTuple *itup,
 			   int attno);
 
 /* gistbuild.c */
-extern Datum gistbuild(PG_FUNCTION_ARGS);
+extern IndexBuildResult *gistbuild(Relation heap, Relation index,
+		  struct IndexInfo *indexInfo);
 extern void gistValidateBufferingOption(char *value);
 
 /* gistbuildbuffers.c */