Create UDF which returns the currently running version

src/backend/distributed/Makefile

@@ -8,7 +8,21 @@ EXTENSION = citus
 EXTVERSIONS = 5.0 5.0-1 5.0-2  \
 	5.1-1 5.1-2 5.1-3 5.1-4 5.1-5 5.1-6 5.1-7 5.1-8 \
 	5.2-1 5.2-2 5.2-3 5.2-4 \
-	6.0-1 6.0-2 6.0-3 6.0-4 6.0-5 6.0-6 6.0-7 6.0-8 6.0-9 6.0-10 6.0-11 6.0-12 6.0-13 6.0-14 6.0-15
+	6.0-1 6.0-2 6.0-3 6.0-4 6.0-5 6.0-6 6.0-7 6.0-8 6.0-9 6.0-10 6.0-11 6.0-12 \
+	6.0-13 6.0-14 6.0-15 6.0-16
+
+ifeq ($(wildcard citus.control),)
+  $(error citus.control not found!)
+endif
+MODVERSION = $(shell grep "default_version" citus.control | grep -oE "'[0-9]+\.[0-9]+-[0-9]+'")
+ifeq ($(MODVERSION),)
+WRONGVERSION = $(shell grep "default_version" citus.control | grep -oE "'.*'")
+  $(warning version $(WRONGVERSION) is incorrect)
+  $(error the version in citus.control should match: \d+.\d+-\d+)
+endif
+CITUS_VERSION = $(shell echo $(MODVERSION) | sed "s/\'//")
+$(info building citus version $(CITUS_VERSION))
+override CFLAGS+=-DCITUS_VERSION=$(CITUS_VERSION)
 
 # All citus--*.sql files in the source directory
 DATA = $(patsubst $(citus_abs_srcdir)/%.sql,%.sql,$(wildcard $(citus_abs_srcdir)/$(EXTENSION)--*--*.sql))
@@ -88,6 +102,8 @@ $(EXTENSION)--6.0-14.sql: $(EXTENSION)--6.0-13.sql $(EXTENSION)--6.0-13--6.0-14.
 	cat $^ > $@
 $(EXTENSION)--6.0-15.sql: $(EXTENSION)--6.0-14.sql $(EXTENSION)--6.0-14--6.0-15.sql
 	cat $^ > $@
+$(EXTENSION)--6.0-16.sql: $(EXTENSION)--6.0-15.sql $(EXTENSION)--6.0-15--6.0-16.sql
+	cat $^ > $@
 
 NO_PGXS = 1
 

src/backend/distributed/citus--6.0-15--6.0-16.sql

@@ -0,0 +1,8 @@
+/* citus--6.0-9--6.0-10.sql */
+
+CREATE FUNCTION citus_running_version()
+  RETURNS text
+  LANGUAGE C IMMUTABLE
+  AS 'MODULE_PATHNAME', $$citus_running_version$$;
+COMMENT ON FUNCTION citus_running_version()
+  IS 'Get the version of the loaded citus module';

src/backend/distributed/citus.control

@@ -1,6 +1,6 @@
 # Citus extension
 comment = 'Citus distributed database'
-default_version = '6.0-15'
+default_version = '6.0-16'
 module_pathname = '$libdir/citus'
 relocatable = false
 schema = pg_catalog

src/backend/distributed/commands/citus_version.c

@@ -0,0 +1,40 @@
+/*-------------------------------------------------------------------------
+ *
+ * create_distributed_relation.c
+ *	  Routines relation to the creation of distributed relations.
+ *
+ * Copyright (c) 2012-2016, Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+#include "lib/stringinfo.h"
+
+#include "utils/builtins.h"
+
+
+/* exports for SQL callable functions */
+PG_FUNCTION_INFO_V1(citus_running_version);
+
+#if !defined(CITUS_VERSION)
+#error Something went wrong, CITUS_VERSION is not set!
+#endif
+
+#define STRINGIFY(x) #x
+#define MACRO(x) STRINGIFY(x)
+
+/*
+ * citus_running_version returns the version string the currently running code was built
+ * with.
+ */
+Datum
+citus_running_version(PG_FUNCTION_ARGS)
+{
+	const char *versionStr = MACRO(CITUS_VERSION);
+	text *versionText = cstring_to_text(versionStr);
+
+	PG_RETURN_TEXT_P(versionText);
+}