From db5f04c4e358fb68e6e9aa45250ccf9f62a973db Mon Sep 17 00:00:00 2001
From: gurkanindibay <gindibay@microsoft.com>
Date: Tue, 26 Dec 2023 07:19:52 +0300
Subject: [PATCH] Adds database comment metadata sync

---
 src/backend/distributed/commands/database.c   | 75 +++++++++++++++++++
 .../distributed/commands/dependencies.c       | 10 +--
 src/include/distributed/commands.h            |  1 +
 3 files changed, 77 insertions(+), 9 deletions(-)

diff --git a/src/backend/distributed/commands/database.c b/src/backend/distributed/commands/database.c
index db40ac7cd..27d5b29d3 100644
--- a/src/backend/distributed/commands/database.c
+++ b/src/backend/distributed/commands/database.c
@@ -13,6 +13,7 @@
 
 #include "miscadmin.h"
 
+#include "access/genam.h"
 #include "access/heapam.h"
 #include "access/htup_details.h"
 #include "access/xact.h"
@@ -45,6 +46,12 @@
 #include "distributed/worker_transaction.h"
 
 
+#include "access/htup_details.h"
+#include "access/table.h"
+#include "catalog/pg_shdescription.h"
+#include "utils/fmgroids.h"
+#include "utils/rel.h"
+
 /*
  * DatabaseCollationInfo is used to store collation related information of a database.
  */
@@ -75,6 +82,7 @@ static ObjectAddress * GetDatabaseAddressFromDatabaseName(char *databaseName,
 														  bool missingOk);
 
 static Oid get_database_owner(Oid dbId);
+static List * GetDatabaseCommentPropagationCommands(Oid databaseOid);
 
 
 /* controlled via GUC */
@@ -569,6 +577,28 @@ GetTablespaceName(Oid tablespaceOid)
 }
 
 
+/*
+ * GetDatabaseMetadataSyncCommands returns a list of sql statements
+ * for the given database id. The list contains the database ddl command,
+ * grant commands and comment propagation commands.
+ */
+List *
+GetDatabaseMetadataSyncCommands(Oid dbOid)
+{
+	char *databaseDDLCommand = CreateDatabaseDDLCommand(dbOid);
+
+	List *ddlCommands = list_make1(databaseDDLCommand);
+
+	List *grantDDLCommands = GrantOnDatabaseDDLCommands(dbOid);
+	List *commentDDLCommands = GetDatabaseCommentPropagationCommands(dbOid);
+
+	ddlCommands = list_concat(ddlCommands, grantDDLCommands);
+	ddlCommands = list_concat(ddlCommands, commentDDLCommands);
+
+	return ddlCommands;
+}
+
+
 /*
  * GetDatabaseCollation gets oid of a database and returns all the collation related information
  * We need this method since collation related info in Form_pg_database is not accessible.
@@ -788,3 +818,48 @@ DatabaseCommentObjectAddress(Node *node, bool missing_ok, bool isPostprocess)
 	*objectAddressCopy = objectAddress;
 	return list_make1(objectAddressCopy);
 }
+
+
+static List *
+GetDatabaseCommentPropagationCommands(Oid databaseOid)
+{
+	Relation shdescRelation;
+	SysScanDesc scan;
+	HeapTuple tuple;
+	List *commands = NIL;
+
+	/* Open pg_shdescription catalog */
+	shdescRelation = table_open(SharedDescriptionRelationId, AccessShareLock);
+
+	/* Scan the table */
+	scan = systable_beginscan(shdescRelation, InvalidOid, false, NULL, 0, NULL);
+	while ((tuple = systable_getnext(scan)) != NULL)
+	{
+		Form_pg_shdescription shdesc = (Form_pg_shdescription) GETSTRUCT(tuple);
+
+		bool isNull = false;
+
+		TupleDesc tupdesc = RelationGetDescr(shdescRelation);
+
+		Datum descDatum = heap_getattr(tuple, Anum_pg_shdescription_description, tupdesc,
+									   &isNull);
+
+		/* Check if the objoid matches the databaseOid */
+		if (shdesc->objoid == databaseOid)
+		{
+			/* Create the SQL command to propagate the comment to other nodes */
+			char *databaseName = get_database_name(databaseOid);
+			char *command = psprintf("COMMENT ON DATABASE %s IS '%s';", databaseName,
+									 TextDatumGetCString(descDatum));
+
+			/* Add the command to the list */
+			commands = lappend(commands, command);
+		}
+	}
+
+	/* End the scan and close the catalog */
+	systable_endscan(scan);
+	table_close(shdescRelation, AccessShareLock);
+
+	return commands;
+}
diff --git a/src/backend/distributed/commands/dependencies.c b/src/backend/distributed/commands/dependencies.c
index d51678c04..6370835c4 100644
--- a/src/backend/distributed/commands/dependencies.c
+++ b/src/backend/distributed/commands/dependencies.c
@@ -478,15 +478,7 @@ GetDependencyCreateDDLCommands(const ObjectAddress *dependency)
 			 */
 			if (dependency->objectId != MyDatabaseId && EnableCreateDatabasePropagation)
 			{
-				char *databaseDDLCommand = CreateDatabaseDDLCommand(dependency->objectId);
-
-				List *ddlCommands = list_make1(databaseDDLCommand);
-
-				List *grantDDLCommands = GrantOnDatabaseDDLCommands(dependency->objectId);
-
-				ddlCommands = list_concat(ddlCommands, grantDDLCommands);
-
-				return ddlCommands;
+				return GetDatabaseMetadataSyncCommands(dependency->objectId);
 			}
 
 			return NIL;
diff --git a/src/include/distributed/commands.h b/src/include/distributed/commands.h
index d927f3615..bdb06b626 100644
--- a/src/include/distributed/commands.h
+++ b/src/include/distributed/commands.h
@@ -230,6 +230,7 @@ extern List * PreprocessAlterDatabaseStmt(Node *node, const char *queryString,
 extern List * PreprocessAlterDatabaseRefreshCollStmt(Node *node, const char *queryString,
 													 ProcessUtilityContext
 													 processUtilityContext);
+extern List * GetDatabaseMetadataSyncCommands(Oid dbOid);
 
 
 extern List * PreprocessAlterDatabaseSetStmt(Node *node, const char *queryString,