From ea3be3a9cf19e08a1e6f5a684f7fcbb6cdb715cf Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Thu, 10 May 2012 14:35:54 +0200
Subject: [PATCH] CData: Added cdata_update().

This function may be used to update an existing data set by "merging" another
data set according to the consolidation function.
---
 src/cdata.c       | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 src/postrr.h.in   |  4 ++++
 src/postrr.sql.in |  5 +++++
 3 files changed, 62 insertions(+)

diff --git a/src/cdata.c b/src/cdata.c
index b47e3f8..32e8e4d 100644
--- a/src/cdata.c
+++ b/src/cdata.c
@@ -80,6 +80,8 @@ PG_FUNCTION_INFO_V1(cdata_typmodout);
 PG_FUNCTION_INFO_V1(cdata_to_cdata);
 PG_FUNCTION_INFO_V1(int32_to_cdata);
 
+PG_FUNCTION_INFO_V1(cdata_update);
+
 /*
  * public API
  */
@@ -329,5 +331,56 @@ int32_to_cdata(PG_FUNCTION_ARGS)
 	PG_RETURN_CDATA_P(data);
 } /* int32_to_cdata */
 
+Datum
+cdata_update(PG_FUNCTION_ARGS)
+{
+	cdata_t *data;
+	cdata_t *update;
+
+	if (PG_NARGS() != 2)
+		ereport(ERROR, (
+					errmsg("cdata_update() expects two arguments"),
+					errhint("Usage: cdata_update(cdata, cdata)")
+				));
+
+	data   = PG_GETARG_CDATA_P(0);
+	update = PG_GETARG_CDATA_P(1);
+
+	if ((data->cf != update->cf) && (update->val_num > 1))
+		ereport(ERROR, (
+					errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					errmsg("invalid update value: incompatible "
+						"consolidation function")
+				));
+
+	switch (data->cf) {
+		case CF_AVG:
+			data->value = (data->value * (data->val_num - data->undef_num))
+				+ (update->value * (update->val_num - update->undef_num));
+			data->value /= (data->val_num - data->undef_num)
+					+  (update->val_num - update->undef_num);
+			break;
+		case CF_MIN:
+			data->value = (data->value <= update->value)
+				? data->value : update->value;
+			break;
+		case CF_MAX:
+			data->value = (data->value >= update->value)
+				? data->value : update->value;
+			break;
+		default:
+			ereport(ERROR, (
+						errcode(ERRCODE_DATA_CORRUPTED),
+						errmsg("unknown consolidation function %d",
+							data->cf)
+					));
+			break;
+	}
+
+	data->undef_num += update->undef_num;
+	data->val_num   += update->val_num;
+	PG_RETURN_CDATA_P(data);
+} /* cdata_update */
+
 /* vim: set tw=78 sw=4 ts=4 noexpandtab : */
 
diff --git a/src/postrr.h.in b/src/postrr.h.in
index bca014a..c309ef0 100644
--- a/src/postrr.h.in
+++ b/src/postrr.h.in
@@ -135,6 +135,10 @@ cdata_to_cdata(PG_FUNCTION_ARGS);
 Datum
 int32_to_cdata(PG_FUNCTION_ARGS);
 
+/* aux. functions */
+Datum
+cdata_update(PG_FUNCTION_ARGS);
+
 #endif /* ! POSTRR_H */
 
 /* vim: set tw=78 sw=4 ts=4 noexpandtab : */
diff --git a/src/postrr.sql.in b/src/postrr.sql.in
index ed51ab6..9339e32 100644
--- a/src/postrr.sql.in
+++ b/src/postrr.sql.in
@@ -280,6 +280,11 @@ CREATE CAST (integer AS cdata)
 	WITH FUNCTION CData(integer, integer, boolean)
 	AS ASSIGNMENT;
 
+CREATE OR REPLACE FUNCTION CData_update(cdata, cdata)
+	RETURNS cdata
+	AS 'postrr-@POSTRR_MAJOR_VERSION@.@POSTRR_MINOR_VERSION@', 'cdata_update'
+	LANGUAGE 'C' IMMUTABLE STRICT;
+
 COMMIT;
 
 SET client_min_messages TO DEFAULT;
-- 
2.30.2