diff -ruN ../base/src/backend/optimizer/path/costsize.c src/backend/optimizer/path/costsize.c
--- ../base/src/backend/optimizer/path/costsize.c	2002-07-04 18:04:57.000000000 +0200
+++ src/backend/optimizer/path/costsize.c	2002-10-03 09:53:06.000000000 +0200
@@ -72,6 +72,7 @@
 double		cpu_tuple_cost = DEFAULT_CPU_TUPLE_COST;
 double		cpu_index_tuple_cost = DEFAULT_CPU_INDEX_TUPLE_COST;
 double		cpu_operator_cost = DEFAULT_CPU_OPERATOR_COST;
+int			index_cost_algorithm = DEFAULT_INDEX_COST_ALGORITHM;
 
 Cost		disable_cost = 100000000.0;
 
@@ -213,8 +214,8 @@
 	Cost		indexStartupCost;
 	Cost		indexTotalCost;
 	Selectivity indexSelectivity;
-	double		indexCorrelation,
-				csquared;
+	double		indexCorrelation;
+	Cost		IO_cost;
 	Cost		min_IO_cost,
 				max_IO_cost;
 	Cost		cpu_per_tuple;
@@ -329,13 +330,62 @@
 	min_IO_cost = ceil(indexSelectivity * T);
 	max_IO_cost = pages_fetched * random_page_cost;
 
-	/*
-	 * Now interpolate based on estimated index order correlation to get
-	 * total disk I/O cost for main table accesses.
-	 */
-	csquared = indexCorrelation * indexCorrelation;
+	switch (index_cost_algorithm) {
+	case 1: {
+		/*
+		** Use abs(correlation) for linear interpolation
+		*/
+		double absC = fabs(indexCorrelation);
+
+		IO_cost = absC * min_IO_cost + (1 - absC) * max_IO_cost;
+	}
+
+	case 2: {
+		/*
+		** First estimate number of pages and cost per page,
+		** then multiply the results.  min_IO_cost is used for
+		** min_pages, because seq_page_cost = 1.
+		*/
+		double absC = fabs(indexCorrelation);
+
+		double estPages = absC * min_IO_cost + (1 - absC) * pages_fetched;
+		double estPCost = absC * 1 + (1 - absC) * random_page_cost;
+		IO_cost = estPages * estPCost;
+	}
+
+	case 3: {
+		/*
+		** Interpolate based on independence squared, thus forcing the
+		** result to be closer to min_IO_cost
+		*/
+		double independence = 1 - fabs(indexCorrelation);
+		double isquared = independence * independence;
+
+		IO_cost = (1 - isquared) * min_IO_cost + isquared * max_IO_cost;
+	}
+
+	case 4: {
+		/*
+		** Interpolate geometrically
+		*/
+		double absC = fabs(indexCorrelation);
+
+		IO_cost = exp(absC * log(min_IO_cost) +
+		              (1 - absC) * log(max_IO_cost));
+	}
+
+	default: {
+		/*
+		 * Interpolate based on estimated index order correlation
+		 * to get total disk I/O cost for main table accesses.
+		 */
+		double csquared = indexCorrelation * indexCorrelation;
+
+		IO_cost = max_IO_cost + csquared * (min_IO_cost - max_IO_cost);
+	}
+	}
 
-	run_cost += max_IO_cost + csquared * (min_IO_cost - max_IO_cost);
+	run_cost += IO_cost;
 
 	/*
 	 * Estimate CPU costs per tuple.
diff -ruN ../base/src/backend/utils/misc/guc.c src/backend/utils/misc/guc.c
--- ../base/src/backend/utils/misc/guc.c	2002-07-20 17:27:19.000000000 +0200
+++ src/backend/utils/misc/guc.c	2002-10-03 10:03:37.000000000 +0200
@@ -644,6 +644,11 @@
 	},
 
 	{
+		{ "index_cost_algorithm", PGC_USERSET }, &index_cost_algorithm,
+		DEFAULT_INDEX_COST_ALGORITHM, 0, INT_MAX, NULL, NULL
+	},
+
+	{
 		{ NULL, 0 }, NULL, 0, 0, 0, NULL, NULL
 	}
 };
diff -ruN ../base/src/include/optimizer/cost.h src/include/optimizer/cost.h
--- ../base/src/include/optimizer/cost.h	2002-06-21 02:12:29.000000000 +0200
+++ src/include/optimizer/cost.h	2002-10-03 09:56:28.000000000 +0200
@@ -24,6 +24,7 @@
 #define DEFAULT_CPU_TUPLE_COST	0.01
 #define DEFAULT_CPU_INDEX_TUPLE_COST 0.001
 #define DEFAULT_CPU_OPERATOR_COST  0.0025
+#define DEFAULT_INDEX_COST_ALGORITHM 3
 
 /* defaults for function attributes used for expensive function calculations */
 #define BYTE_PCT 100
@@ -43,6 +44,7 @@
 extern double cpu_tuple_cost;
 extern double cpu_index_tuple_cost;
 extern double cpu_operator_cost;
+extern int index_cost_algorithm;
 extern Cost disable_cost;
 extern bool enable_seqscan;
 extern bool enable_indexscan;