Separate citus and citus_columnar modules.

Now the modules are independent. Columnar can be loaded by itself, or
along with citus.

src/backend/columnar/columnar_tableam.c

@@ -103,8 +103,8 @@ typedef struct IndexFetchColumnarData
 	MemoryContext scanContext;
 } IndexFetchColumnarData;
 
-
-ColumnarTableSetOptions_hook_type ColumnarTableSetOptions_hook = NULL;
+/* available to other extensions using find_rendezvous_variable() */
+static ColumnarTableSetOptions_hook_type ColumnarTableSetOptions_hook = NULL;
 
 static object_access_hook_type PrevObjectAccessHook = NULL;
 static ProcessUtility_hook_type PrevProcessUtilityHook = NULL;
@@ -1910,6 +1910,11 @@ ColumnarSubXactCallback(SubXactEvent event, SubTransactionId mySubid,
 void
 columnar_tableam_init()
 {
+	ColumnarTableSetOptions_hook_type **ColumnarTableSetOptions_hook_ptr =
+		(ColumnarTableSetOptions_hook_type **) find_rendezvous_variable(
+			"ColumnarTableSetOptions_hook");
+	*ColumnarTableSetOptions_hook_ptr = &ColumnarTableSetOptions_hook;
+
 	RegisterXactCallback(ColumnarXactCallback, NULL);
 	RegisterSubXactCallback(ColumnarSubXactCallback, NULL);
 

src/backend/distributed/Makefile

@@ -19,8 +19,6 @@ DATA_built = $(generated_sql_files)
 
 # directories with source files
 SUBDIRS = . commands connection ddl deparser executor metadata operations planner progress relay safeclib test transaction utils worker
-# columnar modules
-SUBDIRS += ../columnar
 # enterprise modules
 SUBDIRS +=
 
@@ -30,11 +28,9 @@ ENSURE_SUBDIRS_EXIST := $(shell mkdir -p $(SUBDIRS))
 
 # That patsubst rule searches all directories listed in SUBDIRS for .c
 # files, and adds the corresponding .o files to OBJS
-ALL_OBJS = \
+OBJS += \
 	$(patsubst $(citus_abs_srcdir)/%.c,%.o,$(foreach dir,$(SUBDIRS), $(sort $(wildcard $(citus_abs_srcdir)/$(dir)/*.c))))
 
-OBJS += $(filter-out ../columnar/mod.o,$(ALL_OBJS))
-
 # be explicit about the default target
 all:
 

src/backend/distributed/commands/alter_table.c

@@ -52,6 +52,7 @@
 #include "distributed/multi_partitioning_utils.h"
 #include "distributed/reference_table_utils.h"
 #include "distributed/relation_access_tracking.h"
+#include "distributed/shared_library_init.h"
 #include "distributed/shard_utils.h"
 #include "distributed/worker_protocol.h"
 #include "distributed/worker_transaction.h"
@@ -687,7 +688,7 @@ ConvertTable(TableConversionState *con)
 		strcmp(con->originalAccessMethod, "columnar") == 0)
 	{
 		ColumnarOptions options = { 0 };
-		ReadColumnarOptions(con->relationId, &options);
+		ExternReadColumnarOptions(con->relationId, &options);
 
 		ColumnarTableDDLContext *context = (ColumnarTableDDLContext *) palloc0(
 			sizeof(ColumnarTableDDLContext));
@@ -843,7 +844,7 @@ DropIndexesNotSupportedByColumnar(Oid relationId, bool suppressNoticeMessages)
 	foreach_oid(indexId, indexIdList)
 	{
 		char *indexAmName = GetIndexAccessMethodName(indexId);
-		if (ColumnarSupportsIndexAM(indexAmName))
+		if (ExternColumnarSupportsIndexAM(indexAmName))
 		{
 			continue;
 		}

src/backend/distributed/operations/node_protocol.c

@@ -48,6 +48,7 @@
 #include "distributed/metadata_sync.h"
 #include "distributed/namespace_utils.h"
 #include "distributed/pg_dist_shard.h"
+#include "distributed/shared_library_init.h"
 #include "distributed/version_compat.h"
 #include "distributed/worker_manager.h"
 #include "foreign/foreign.h"
@@ -613,7 +614,7 @@ GetPreLoadTableCreationCommands(Oid relationId,
 
 
 	/* add columnar options for cstore tables */
-	if (accessMethod == NULL && IsColumnarTableAmTable(relationId))
+	if (accessMethod == NULL && ExternIsColumnarTableAmTable(relationId))
 	{
 		TableDDLCommand *cstoreOptionsDDL = ColumnarGetTableOptionsDDL(relationId);
 		if (cstoreOptionsDDL != NULL)
@@ -1047,7 +1048,8 @@ CitusCreateAlterColumnarTableSet(char *qualifiedRelationName,
 					 options->chunkRowCount,
 					 options->stripeRowCount,
 					 options->compressionLevel,
-					 quote_literal_cstr(CompressionTypeStr(options->compressionType)));
+					 quote_literal_cstr(ExternCompressionTypeStr(
+											options->compressionType)));
 
 	return buf.data;
 }
@@ -1136,7 +1138,7 @@ ColumnarGetTableOptionsDDL(Oid relationId)
 	char *relationName = get_rel_name(relationId);
 
 	ColumnarOptions options = { 0 };
-	ReadColumnarOptions(relationId, &options);
+	ExternReadColumnarOptions(relationId, &options);
 
 	return ColumnarGetCustomTableOptionsDDL(schemaName, relationName, options);
 }

src/backend/distributed/shared_library_init.c

@@ -100,6 +100,37 @@
 /* marks shared object as one loadable by the postgres version compiled against */
 PG_MODULE_MAGIC;
 
+ColumnarSupportsIndexAM_type ExternColumnarSupportsIndexAM = NULL;
+CompressionTypeStr_type ExternCompressionTypeStr = NULL;
+IsColumnarTableAmTable_type ExternIsColumnarTableAmTable = NULL;
+ReadColumnarOptions_type ExternReadColumnarOptions = NULL;
+
+/*
+ * Define "pass-through" functions so that a SQL function defined as one of
+ * these symbols in the citus module can use the definition in the columnar
+ * module.
+ */
+#define DEFINE_COLUMNAR_PASSTHROUGH_FUNC(funcname) \
+	static PGFunction CppConcat(extern_, funcname); \
+	PG_FUNCTION_INFO_V1(funcname); \
+	Datum funcname(PG_FUNCTION_ARGS) \
+	{ \
+		return CppConcat(extern_, funcname)(fcinfo); \
+	}
+#define INIT_COLUMNAR_PASSTHROUGH_SYMBOL(funcname) \
+	CppConcat(extern_, funcname) = load_external_function( \
+		COLUMNAR_MODULE_NAME, # funcname, true, &handle)
+
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_handler)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(alter_columnar_table_set)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(alter_columnar_table_reset)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(upgrade_columnar_storage)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(downgrade_columnar_storage)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_relation_storageid)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_storage_info)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(columnar_store_memory_stats)
+DEFINE_COLUMNAR_PASSTHROUGH_FUNC(test_columnar_storage_write_new_page)
+
 #define DUMMY_REAL_TIME_EXECUTOR_ENUM_VALUE 9999999
 static char *CitusVersion = CITUS_VERSION;
 
@@ -323,12 +354,6 @@ _PG_init(void)
 	original_client_auth_hook = ClientAuthentication_hook;
 	ClientAuthentication_hook = CitusAuthHook;
 
-	/*
-	 * When the options change on a columnar table, we may need to propagate
-	 * the changes to shards.
-	 */
-	ColumnarTableSetOptions_hook = ColumnarTableSetOptionsHook;
-
 	InitializeMaintenanceDaemon();
 
 	/* initialize coordinated transaction management */
@@ -357,7 +382,56 @@ _PG_init(void)
 	{
 		DoInitialCleanup();
 	}
-	columnar_init();
+
+	/* ensure columnar module is loaded at the right time */
+	load_file(COLUMNAR_MODULE_NAME, false);
+
+	/*
+	 * Now, acquire symbols from columnar module. First, acquire
+	 * the address of the set options hook, and set it so that we
+	 * can propagate options changes.
+	 */
+	ColumnarTableSetOptions_hook_type **ColumnarTableSetOptions_hook_ptr =
+		(ColumnarTableSetOptions_hook_type **) find_rendezvous_variable(
+			"ColumnarTableSetOptions_hook");
+
+	/* rendezvous variable registered during columnar initialization */
+	Assert(ColumnarTableSetOptions_hook_ptr != NULL);
+	Assert(*ColumnarTableSetOptions_hook_ptr != NULL);
+
+	**ColumnarTableSetOptions_hook_ptr = ColumnarTableSetOptionsHook;
+
+	/*
+	 * Acquire symbols for columnar functions that citus calls.
+	 */
+	void *handle = NULL;
+	ExternColumnarSupportsIndexAM = (ColumnarSupportsIndexAM_type) (void *)
+									load_external_function(COLUMNAR_MODULE_NAME,
+														   "ColumnarSupportsIndexAM",
+														   true, &handle);
+	ExternCompressionTypeStr = (CompressionTypeStr_type) (void *)
+							   load_external_function(COLUMNAR_MODULE_NAME,
+													  "CompressionTypeStr",
+													  true, &handle);
+	ExternIsColumnarTableAmTable = (IsColumnarTableAmTable_type) (void *)
+								   load_external_function(COLUMNAR_MODULE_NAME,
+														  "IsColumnarTableAmTable",
+														  true, &handle);
+	ExternReadColumnarOptions = (ReadColumnarOptions_type) (void *)
+								load_external_function(COLUMNAR_MODULE_NAME,
+													   "ReadColumnarOptions",
+													   true, &handle);
+
+	/* initialize symbols for "pass-through" functions */
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(columnar_handler);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(alter_columnar_table_set);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(alter_columnar_table_reset);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(upgrade_columnar_storage);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(downgrade_columnar_storage);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(columnar_relation_storageid);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(columnar_storage_info);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(columnar_store_memory_stats);
+	INIT_COLUMNAR_PASSTHROUGH_SYMBOL(test_columnar_storage_write_new_page);
 }
 
 

src/include/columnar/columnar.h

@@ -25,6 +25,8 @@
 #include "columnar/columnar_compression.h"
 #include "columnar/columnar_metadata.h"
 
+#define COLUMNAR_MODULE_NAME "citus_columnar"
+
 /* Defines for valid option names */
 #define OPTION_NAME_COMPRESSION_TYPE "compression"
 #define OPTION_NAME_STRIPE_ROW_COUNT "stripe_row_limit"
@@ -187,6 +189,10 @@ typedef enum StripeWriteStateEnum
 	STRIPE_WRITE_IN_PROGRESS
 } StripeWriteStateEnum;
 
+typedef bool (*ColumnarSupportsIndexAM_type)(char *);
+typedef const char *(*CompressionTypeStr_type)(CompressionType);
+typedef bool (*IsColumnarTableAmTable_type)(Oid);
+typedef bool (*ReadColumnarOptions_type)(Oid, ColumnarOptions *);
 
 /* ColumnarReadState represents state of a columnar scan. */
 struct ColumnarReadState;
@@ -205,7 +211,6 @@ extern int columnar_compression_level;
 
 /* called when the user changes options on the given relation */
 typedef void (*ColumnarTableSetOptions_hook_type)(Oid relid, ColumnarOptions options);
-extern ColumnarTableSetOptions_hook_type ColumnarTableSetOptions_hook;
 
 extern void columnar_init(void);
 extern void columnar_init_gucs(void);
@@ -316,5 +321,4 @@ extern bool PendingWritesInUpperTransactions(Oid relfilenode,
 											 SubTransactionId currentSubXid);
 extern MemoryContext GetWriteContextForDebug(void);
 
-
 #endif /* COLUMNAR_H */

src/include/distributed/shared_library_init.h

@@ -11,10 +11,17 @@
 #ifndef SHARED_LIBRARY_INIT_H
 #define SHARED_LIBRARY_INIT_H
 
+#include "columnar/columnar.h"
+
 #define GUC_STANDARD 0
 #define MAX_SHARD_COUNT 64000
 #define MAX_SHARD_REPLICATION_FACTOR 100
 
+extern ColumnarSupportsIndexAM_type ExternColumnarSupportsIndexAM;
+extern CompressionTypeStr_type ExternCompressionTypeStr;
+extern IsColumnarTableAmTable_type ExternIsColumnarTableAmTable;
+extern ReadColumnarOptions_type ExternReadColumnarOptions;
+
 extern void StartupCitusBackend(void);
 
 #endif /* SHARED_LIBRARY_INIT_H */

src/test/regress/expected/columnar_create.out

@@ -185,11 +185,5 @@ SELECT columnar_test_helpers.columnar_metadata_has_storage_id(:columnar_temp_sto
  f
 (1 row)
 
---
--- Will throw error due to redefining GUCs, because citus is already
--- loaded and has already initialized columnar code. This test is to
--- ensure that the citus_columnar module is built and present, and
--- that it can be loaded without link failures.
---
+-- make sure citus_columnar can be loaded
 LOAD 'citus_columnar';
-ERROR:  attempt to redefine parameter "columnar.compression"

src/test/regress/sql/columnar_create.sql

@@ -130,10 +130,5 @@ SELECT COUNT(*)=0 FROM columnar_temp;
 -- since we deleted all the rows, we shouldn't have any stripes for table
 SELECT columnar_test_helpers.columnar_metadata_has_storage_id(:columnar_temp_storage_id);
 
---
--- Will throw error due to redefining GUCs, because citus is already
--- loaded and has already initialized columnar code. This test is to
--- ensure that the citus_columnar module is built and present, and
--- that it can be loaded without link failures.
---
+-- make sure citus_columnar can be loaded
 LOAD 'citus_columnar';