/*-------------------------------------------------------------------------
 *
 * indexam.c--
 *    general index access method routines
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/access/index/indexam.c,v 1.11 1997/08/12 22:51:48 momjian Exp $
 *
 * INTERFACE ROUTINES
 *	index_open 	- open an index relation by relationId
 *	index_openr 	- open a index relation by name
 *	index_close 	- close a index relation
 *	index_beginscan - start a scan of an index
 *	index_rescan  	- restart a scan of an index
 *	index_endscan 	- end a scan
 *	index_insert 	- insert an index tuple into a relation
 *	index_delete 	- delete an item from an index relation
 *	index_markpos  	- mark a scan position
 *	index_restrpos  - restore a scan position
 *	index_getnext 	- get the next tuple from a scan
 * **	index_fetch	- retrieve tuple with tid
 * **	index_replace	- replace a tuple
 * **	index_getattr	- get an attribute from an index tuple
 *	index_getprocid - get a support procedure id from the rel tuple
 *	
 *	IndexScanIsValid - check index scan
 *
 * NOTES
 *	This file contains the index_ routines which used
 *	to be a scattered collection of stuff in access/genam.
 *
 *	The ** routines: index_fetch, index_replace, and index_getattr
 *	have not yet been implemented.  They may not be needed.
 *
 * old comments
 * 	Scans are implemented as follows:
 *
 * 	`0' represents an invalid item pointer.
 * 	`-' represents an unknown item pointer.
 * 	`X' represents a known item pointers.
 * 	`+' represents known or invalid item pointers.
 * 	`*' represents any item pointers.
 *
 * 	State is represented by a triple of these symbols in the order of
 * 	previous, current, next.  Note that the case of reverse scans works
 * 	identically.
 *
 *		State	Result
 * 	(1)	+ + -	+ 0 0		(if the next item pointer is invalid)
 * 	(2)		+ X -		(otherwise)
 * 	(3)	* 0 0	* 0 0		(no change)
 * 	(4)	+ X 0	X 0 0		(shift)
 * 	(5)	* + X	+ X -		(shift, add unknown)
 *
 * 	All other states cannot occur.
 *
 * 	Note: It would be possible to cache the status of the previous and
 *	      next item pointer using the flags.
 *
 *-------------------------------------------------------------------------
 */

#include <postgres.h>
 
#include <access/genam.h>  
#include <utils/relcache.h>
#include <fmgr.h>
#include <storage/lmgr.h>
#include <access/heaptuple.h>

/* ----------------
 *   undefine macros we aren't going to use that would otherwise
 *   get in our way..  delete is defined in c.h and the am's are
 *   defined in heapam.h
 * ----------------
 */
#undef delete
#undef aminsert
#undef amdelete
#undef ambeginscan
#undef amrescan
#undef amendscan
#undef ammarkpos
#undef amrestrpos
#undef amgettuple

/* ----------------------------------------------------------------
 *		    macros used in index_ routines
 * ----------------------------------------------------------------
 */
#define RELATION_CHECKS \
Assert(RelationIsValid(relation)); \
	 Assert(PointerIsValid(relation->rd_am))
     
#define SCAN_CHECKS \
     Assert(IndexScanIsValid(scan)); \
	 Assert(RelationIsValid(scan->relation)); \
	 Assert(PointerIsValid(scan->relation->rd_am))
     
#define GET_REL_PROCEDURE(x,y) \
	 procedure = relation->rd_am->y; \
	 if (! RegProcedureIsValid(procedure)) \
	 elog(WARN, "index_%s: invalid %s regproc", \
	      CppAsString(x), CppAsString(y))
     
#define GET_SCAN_PROCEDURE(x,y) \
	 procedure = scan->relation->rd_am->y; \
	 if (! RegProcedureIsValid(procedure)) \
	 elog(WARN, "index_%s: invalid %s regproc", \
	      CppAsString(x), CppAsString(y))
     
     
/* ----------------------------------------------------------------
 *		   index_ interface functions
 * ----------------------------------------------------------------
 */
/* ----------------
 *	index_open - open an index relation by relationId
 *
 *	presently the relcache routines do all the work we need
 *	to open/close index relations.
 * ----------------
 */
Relation
index_open(Oid relationId)
{
    return RelationIdGetRelation(relationId);
}

/* ----------------
 *	index_openr - open a index relation by name
 *
 *	presently the relcache routines do all the work we need
 *	to open/close index relations.
 * ----------------
 */
Relation
index_openr(char *relationName)
{
    return RelationNameGetRelation(relationName);
}

/* ----------------
 *	index_close - close a index relation
 *
 *	presently the relcache routines do all the work we need
 *	to open/close index relations.
 * ----------------
 */
void
index_close(Relation relation)
{
    RelationClose(relation);
}

/* ----------------
 *	index_insert - insert an index tuple into a relation
 * ----------------
 */
InsertIndexResult
index_insert(Relation relation,
	     Datum *datum,
	     char *nulls,
	     ItemPointer heap_t_ctid,
	     Relation heapRel)
{
    RegProcedure		procedure;
    InsertIndexResult		specificResult;
    
    RELATION_CHECKS;
    GET_REL_PROCEDURE(insert,aminsert);
    
    /* ----------------
     *	have the am's insert proc do all the work.  
     * ----------------
     */
    specificResult = (InsertIndexResult)
	fmgr(procedure, relation, datum, nulls, heap_t_ctid, heapRel, NULL);
    
    /* ----------------
     *	the insert proc is supposed to return a "specific result" and
     *  this routine has to return a "general result" so after we get
     *  something back from the insert proc, we allocate a
     *  "general result" and copy some crap between the two.
     *
     *  As far as I'm concerned all this result shit is needlessly c
     *  omplicated and should be eliminated.  -cim 1/19/91
     *
     *  mao concurs.  regardless of how we feel here, however, it is
     *  important to free memory we don't intend to return to anyone.
     *  2/28/91
     *
     *  this "general result" crap is now gone. -ay 3/6/95
     * ----------------
     */
    
    return (specificResult);
}

/* ----------------
 *	index_delete - delete an item from an index relation
 * ----------------
 */
void
index_delete(Relation relation, ItemPointer indexItem)
{
    RegProcedure	procedure;
    
    RELATION_CHECKS;
    GET_REL_PROCEDURE(delete,amdelete);
    
    fmgr(procedure, relation, indexItem);    
}

/* ----------------
 *	index_beginscan - start a scan of an index
 * ----------------
 */
IndexScanDesc
index_beginscan(Relation relation,
		bool scanFromEnd,
		uint16 numberOfKeys,
		ScanKey key)
{
    IndexScanDesc	scandesc;
    RegProcedure	procedure;
    
    RELATION_CHECKS;
    GET_REL_PROCEDURE(beginscan,ambeginscan);
    
    RelationSetRIntentLock(relation);
    
    scandesc = (IndexScanDesc)
	fmgr(procedure, relation, scanFromEnd, numberOfKeys, key);
    
    return scandesc;
}

/* ----------------
 *	index_rescan  - restart a scan of an index
 * ----------------
 */
void
index_rescan(IndexScanDesc scan, bool scanFromEnd, ScanKey key)
{
    RegProcedure	procedure;
    
    SCAN_CHECKS;
    GET_SCAN_PROCEDURE(rescan,amrescan);
    
    fmgr(procedure, scan, scanFromEnd, key);
}

/* ----------------
 *	index_endscan - end a scan
 * ----------------
 */
void
index_endscan(IndexScanDesc scan)
{
    RegProcedure	procedure;
    
    SCAN_CHECKS;
    GET_SCAN_PROCEDURE(endscan,amendscan);
    
    fmgr(procedure, scan);
    
    RelationUnsetRIntentLock(scan->relation);
}

/* ----------------
 *	index_markpos  - mark a scan position
 * ----------------
 */
void
index_markpos(IndexScanDesc scan)
{
    RegProcedure	procedure;
    
    SCAN_CHECKS;
    GET_SCAN_PROCEDURE(markpos,ammarkpos);
    
    fmgr(procedure, scan);
}

/* ----------------
 *	index_restrpos  - restore a scan position
 * ----------------
 */
void
index_restrpos(IndexScanDesc scan)
{
    RegProcedure	procedure;
    
    SCAN_CHECKS;
    GET_SCAN_PROCEDURE(restrpos,amrestrpos);
    
    fmgr(procedure, scan);
}

/* ----------------
 *	index_getnext - get the next tuple from a scan
 *
 *  	A RetrieveIndexResult is a index tuple/heap tuple pair
 * ----------------
 */
RetrieveIndexResult
index_getnext(IndexScanDesc scan,
	      ScanDirection direction)
{
    RegProcedure		procedure;
    RetrieveIndexResult		result;
    
    SCAN_CHECKS;
    GET_SCAN_PROCEDURE(getnext,amgettuple);
    
    /* ----------------
     *	have the am's gettuple proc do all the work.  
     * ----------------
     */
    result = (RetrieveIndexResult)
	fmgr(procedure, scan, direction);
    
    return result;
}

/* ----------------
 *	index_getprocid
 *
 *	Some indexed access methods may require support routines that are
 *	not in the operator class/operator model imposed by pg_am.  These
 *	access methods may store the OIDs of registered procedures they
 *	need in pg_amproc.  These registered procedure OIDs are ordered in
 *	a way that makes sense to the access method, and used only by the
 *	access method.  The general index code doesn't know anything about
 *	the routines involved; it just builds an ordered list of them for
 *	each attribute on which an index is defined.
 *
 *	This routine returns the requested procedure OID for a particular
 *	indexed attribute.
 * ----------------
 */
RegProcedure
index_getprocid(Relation irel,
		AttrNumber attnum,
		uint16 procnum)
{
    RegProcedure *loc;
    int natts;
    
    natts = irel->rd_rel->relnatts;
    
    loc = irel->rd_support;

    Assert(loc != NULL);
    
    return (loc[(natts * (procnum - 1)) + (attnum - 1)]);
}

Datum
GetIndexValue(HeapTuple tuple,
	      TupleDesc hTupDesc,
	      int attOff,
	      AttrNumber attrNums[],
	      FuncIndexInfo *fInfo,
	      bool *attNull,
	      Buffer buffer)
{
    Datum returnVal;
    bool	isNull;
    
    if (PointerIsValid(fInfo) && FIgetProcOid(fInfo) != InvalidOid) {
	int i;
	Datum *attData = (Datum *)palloc(FIgetnArgs(fInfo)*sizeof(Datum));
	
	for (i = 0; i < FIgetnArgs(fInfo); i++) {
	    attData[i] = (Datum) heap_getattr(tuple, 
					      buffer, 
					      attrNums[i], 
					      hTupDesc,
					      attNull);
	}
	returnVal = (Datum)fmgr_array_args(FIgetProcOid(fInfo),
					   FIgetnArgs(fInfo),
					   (char **) attData,
					   &isNull);
	pfree(attData);
	*attNull = FALSE;
    }else {
	returnVal = (Datum) heap_getattr(tuple, buffer, attrNums[attOff], 
					 hTupDesc, attNull);
    }
    return returnVal;
}
