Fix various build issues

I came across several places we weren't as flexible or resilient as we
should have been in our build logic. They include:

  * Not using `DESTDIR` in the install-header destination
  * Allowing callers to specify `VPATH` or `srcdir` (which breaks)
  * Using absolute path for SCRIPTS (9.5 prepends srcdir)
  * Including libpq-int in a confusing way (extracted this function)
  * Having server includes come first during csql build (client must)

In particular, I hit all of these attempting to build with pg_buildext
in Debian. It passes in an explicit VPATH, as well as srcdir (breaking
all recursive make invocations), and also uses DESTDIR during install.

In addition, a PGDG-enabled Debian box will have the latest libpq-dev
headers (e.g. 9.5) even when building against an older server version
(e.g. 9.4). This leads to problems when including e.g. `c.h`, which
is ambiguous. While compiling more client-side code (csql), we need to
ensure the newer libpq headers are included _first_, so I fixed that.

Makefile

@@ -18,11 +18,11 @@ extension:
 install-extension: extension
 	$(MAKE) -C src/backend/distributed/ install
 install-headers: extension
-	$(MKDIR_P) '$(includedir_server)/distributed/'
+	$(MKDIR_P) '$(DESTDIR)$(includedir_server)/distributed/'
 # generated headers are located in the build directory
-	$(INSTALL_DATA) src/include/citus_config.h '$(includedir_server)/'
+	$(INSTALL_DATA) src/include/citus_config.h '$(DESTDIR)$(includedir_server)/'
 # the rest in the source tree
-	$(INSTALL_DATA) $(citus_abs_srcdir)/src/include/distributed/*.h '$(includedir_server)/distributed/'
+	$(INSTALL_DATA) $(citus_abs_srcdir)/src/include/distributed/*.h '$(DESTDIR)$(includedir_server)/distributed/'
 clean-extension:
 	$(MAKE) -C src/backend/distributed/ clean
 .PHONY: extension install-extension clean-extension

Makefile.global.in

@@ -17,9 +17,10 @@ PGXS:=$(shell $(PG_CONFIG) --pgxs)
 # Support for VPATH builds (i.e. builds from outside the source tree)
 vpath_build=@vpath_build@
 ifeq ($(vpath_build),yes)
-	VPATH:=$(citus_abs_srcdir)
+	override VPATH:=$(citus_abs_srcdir)
 	USE_VPATH:=$(VPATH)
 	citus_top_srcdir:=$(citus_abs_top_srcdir)
+	override srcdir=$(VPATH)
 else
 	citus_top_srcdir:=$(citus_top_builddir)
 endif

src/backend/distributed/Makefile

@@ -7,8 +7,7 @@ MODULE_big = citus
 EXTENSION = citus
 EXTVERSION = 5.0
 DATA_built = $(EXTENSION)--$(EXTVERSION).sql
-# Install scripts in build and/or source directory, but only once if those are the same
+SCRIPTS = ../../bin/scripts/copy_to_distributed_table
-SCRIPTS = $(sort $(wildcard $(citus_top_builddir)/src/bin/scripts/* $(citus_top_srcdir)/src/bin/scripts/*))
 
 # directories with source files
 SUBDIRS = . commands executor master planner relay test utils worker

src/backend/distributed/test/connection_cache.c

@@ -13,7 +13,8 @@
 #include "postgres.h"
 #include "c.h"
 #include "fmgr.h"
-#include "libpq-int.h"
+
+#include "libpq-fe.h"
 
 #include <stddef.h>
 #include <string.h>
@@ -143,7 +144,7 @@ set_connection_status_bad(PG_FUNCTION_ARGS)
 	}
 
 	/* set the connection status */
-	connection->status = CONNECTION_BAD;
+	SetConnectionStatus(connection, CONNECTION_BAD);
 
 	PG_RETURN_BOOL(true);
 }

src/backend/distributed/test/connection_utils.c

@@ -0,0 +1,31 @@
+/*-------------------------------------------------------------------------
+ *
+ * test/src/connection_utils.c
+ *
+ * This file isolates a test function which modifies private connection
+ * state, ensuring the correct ("internal") headers are included, rather
+ * than the version-specific server ones. Without this kludge, builds on
+ * certain platforms (those which install a single libpq version but can
+ * have multiple PostgreSQL server versions) will faile.
+ *
+ * Copyright (c) 2014-2015, Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "internal/c.h"
+#include "libpq-fe.h"
+#include "internal/libpq-int.h"
+
+#include "distributed/test_helper_functions.h"
+
+/*
+ * SetConnectionStatus simply uses the internal headers to access "private"
+ * fields of the connection struct in order to force a cache connection to a
+ * particular status.
+ */
+void
+SetConnectionStatus(PGconn *connection, ConnStatusType status)
+{
+	connection->status = status;
+}

src/bin/csql/Makefile

@@ -28,7 +28,10 @@ PG_LIBS = $(libpq)
 
 include $(citus_top_builddir)/Makefile.global
 
-override CPPFLAGS += -I$(libpq_srcdir) -I$(top_srcdir)/src/bin/csql
+# ensure client includes occur before server
+client_includes := $(shell $(PG_CONFIG) --includedir)/internal
+
+override CPPFLAGS := -I$(client_includes) -I$(libpq_srcdir) -I$(citus_abs_top_srcdir)/src/bin/csql $(CPPFLAGS)
 
 # psqlscan is compiled as part of mainloop
 mainloop.o: psqlscan.c

src/include/distributed/test_helper_functions.h

@@ -16,6 +16,7 @@
 #include "postgres.h"
 #include "c.h"
 #include "fmgr.h"
+#include "libpq-fe.h"
 
 #include "utils/array.h"
 
@@ -29,6 +30,7 @@
 /* function declarations for generic test functions */
 extern ArrayType * DatumArrayToArrayType(Datum *datumArray, int datumCount,
 										 Oid datumTypeId);
+extern void SetConnectionStatus(PGconn *connection, ConnStatusType status);
 
 /* fake FDW for use in tests */
 extern Datum fake_fdw_handler(PG_FUNCTION_ARGS);