[#23648] YSQL: Intoduce shared data between pggate in parallel leader and workers

Summary:
Current diff is a preparation diff. The fix for the  #23648 issue will be landed separately.

The fix of the #23648 issue is required all perform operations has unique serial number. In this case local t-server will be able to wait/reorder operations before execution in case `op_2` will arrive earlier than `op_1`.
The `uint64_t` counter is used to provider serial number for each new perform operation.
But because postgres's background workers uses same `PgClientSession` object (pg worker process uses same `session_id` as parallel leader process) it is required to share this counter among multiple postgres process.
Postgres has the `PROC` structure which is assigned to each process. This structure is stored in shared memory. It is reasonable to place perform serial number counter in this structure.
This diff reserves some amount of raw data inside `PROC` structure (i.e. data plcaceholder) and provide access to this data to `pggate` during initialization.
`pggate` constructs required objects in this raw data and use them as regular C++ structures (i.e. `std::atomic<uint64_t>` for perform serial number counter instead of `pg_atomic_uint64` or similar).

**Note:**
- the diff changes the time when pggate object is destroyed (see the call of `YBOnPostgresBackendShutdown()` function). Because pggate uses data in `PROC` it must be destroyed before this structure will be cleared
- the diff restores original postgres's interface for the `InitPostgres` process (i.e. `session_id` argument is removed).

Upgrade/Rollback safety:
The `pg_client.proto` is used for communication between pggate and local t-server only. So any modification of the this file are upgrade/rollback safe.
Jira: DB-12559

Test Plan: Jenkins

Reviewers: amartsinchyk, pjain, kramanathan, sergei, jason

Reviewed By: amartsinchyk

Subscribers: jason, yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D46542

Author: d-uspenskiy

src/postgres/src/backend/access/transam/parallel.c

@@ -1461,12 +1461,23 @@ ParallelWorkerMain(Datum main_arg)
 	 * (b) we do not want parallel mode to cause these failures, because that
 	 * would make use of parallel query plans not transparent to applications.
 	 */
-	YbBackgroundWorkerInitializeConnectionByOid(fps->database_id,
-												fps->authenticated_user_id,
-												(fps->parallel_master_is_yb_session ?
-												 &fps->parallel_master_yb_session_state.session_id :
-												 NULL),
-												BGWORKER_BYPASS_ALLOWCONN);
+	if (fps->parallel_master_is_yb_session)
+	{
+		YbcPgInitPostgresInfo yb_init_info = {
+			.parallel_leader_session_id = &fps->parallel_master_yb_session_state.session_id,
+			.shared_data = &fps->parallel_leader_pgproc->yb_shared_data
+		};
+		YbBackgroundWorkerInitializeConnectionByOid(fps->database_id,
+													fps->authenticated_user_id,
+													BGWORKER_BYPASS_ALLOWCONN,
+													&yb_init_info);
+	}
+	else
+	{
+		BackgroundWorkerInitializeConnectionByOid(fps->database_id,
+												  fps->authenticated_user_id,
+												  BGWORKER_BYPASS_ALLOWCONN);
+	}
 
 	/*
 	 * Set the client encoding to the database encoding, since that is what

src/postgres/src/backend/bootstrap/bootstrap.c

@@ -363,7 +363,7 @@ BootstrapModeMain(int argc, char *argv[], bool check_only)
 	if (pg_link_canary_is_frontend())
 		elog(ERROR, "backend is incorrectly linked to frontend functions");
 
-	InitPostgres(NULL, InvalidOid, NULL, InvalidOid, false, false, NULL, NULL);
+	InitPostgres(NULL, InvalidOid, NULL, InvalidOid, false, false, NULL);
 
 	/* Initialize stuff for bootstrap-file processing */
 	for (i = 0; i < MAXATTR; i++)

src/postgres/src/backend/postmaster/autovacuum.c

@@ -476,7 +476,7 @@ AutoVacLauncherMain(int argc, char *argv[])
 	/* Early initialization */
 	BaseInit();
 
-	InitPostgres(NULL, InvalidOid, NULL, InvalidOid, false, false, NULL, NULL);
+	InitPostgres(NULL, InvalidOid, NULL, InvalidOid, false, false, NULL);
 
 	SetProcessingMode(NormalProcessing);
 
@@ -1702,8 +1702,7 @@ AutoVacWorkerMain(int argc, char *argv[])
 		 * Note: if we have selected a just-deleted database (due to using
 		 * stale stats info), we'll fail and exit here.
 		 */
-		InitPostgres(NULL, dbid, NULL, InvalidOid, false, true,
-					 dbname, NULL);
+		InitPostgres(NULL, dbid, NULL, InvalidOid, false, true, dbname);
 		SetProcessingMode(NormalProcessing);
 		set_ps_display(dbname);
 		ereport(DEBUG1,

src/postgres/src/backend/postmaster/postmaster.c

@@ -6166,8 +6166,7 @@ BackgroundWorkerInitializeConnection(const char *dbname, const char *username, u
 				 username, InvalidOid,	/* role to connect as */
 				 false,			/* never honor session_preload_libraries */
 				 (flags & BGWORKER_BYPASS_ALLOWCONN) != 0,	/* ignore datallowconn? */
-				 NULL,			/* no out_dbname */
-				 NULL);			/* session id */
+				 NULL			/* no out_dbname */ );
 
 	if (yb_enable_ash)
 		YbAshSetMetadataForBgworkers();
@@ -6183,8 +6182,8 @@ BackgroundWorkerInitializeConnection(const char *dbname, const char *username, u
  * Connect background worker to a database using OIDs.
  */
 void
-YbBackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid,
-											uint64_t *session_id, uint32 flags)
+YbBackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid, uint32 flags,
+								const YbcPgInitPostgresInfo *yb_init_info)
 {
 	BackgroundWorker *worker = MyBgworkerEntry;
 
@@ -6194,12 +6193,12 @@ YbBackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid,
 				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
 				 errmsg("database connection requirement not indicated during registration")));
 
-	InitPostgres(NULL, dboid,	/* database to connect to */
+	YbInitPostgres(NULL, dboid,	/* database to connect to */
 				 NULL, useroid, /* role to connect as */
 				 false,			/* never honor session_preload_libraries */
 				 (flags & BGWORKER_BYPASS_ALLOWCONN) != 0,	/* ignore datallowconn? */
 				 NULL,			/* no out_dbname */
-				 session_id);	/* session id */
+				 yb_init_info);
 
 	if (yb_enable_ash)
 		YbAshSetMetadataForBgworkers();
@@ -6215,7 +6214,7 @@ void
 BackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid,
 										  uint32 flags)
 {
-	YbBackgroundWorkerInitializeConnectionByOid(dboid, useroid, NULL, flags);
+	YbBackgroundWorkerInitializeConnectionByOid(dboid, useroid, flags, NULL);
 }
 
 /*

src/postgres/src/backend/storage/ipc/ipc.c

@@ -155,9 +155,6 @@ proc_exit(int code)
 	}
 #endif
 
-	if (IsYugaByteEnabled())
-		YBOnPostgresBackendShutdown();
-
 	elog(DEBUG3, "exit(%d)", code);
 
 	exit(code);

src/postgres/src/backend/storage/lmgr/proc.c

@@ -56,6 +56,9 @@
 #include "utils/timeout.h"
 #include "utils/timestamp.h"
 
+/* YB includes */
+#include "pg_yb_utils.h"
+
 /* GUC variables */
 int			DeadlockTimeout = 1000;
 int			StatementTimeout = 0;
@@ -910,6 +913,9 @@ ProcKill(int code, Datum arg)
 	MyProc = NULL;
 	DisownLatch(&proc->procLatch);
 
+	if (IsYugaByteEnabled())
+		YBOnPostgresBackendShutdown();
+
 	ReleaseProcToFreeList(proc);
 
 	/*

src/postgres/src/backend/tcop/postgres.c

@@ -6058,8 +6058,7 @@ PostgresMain(const char *dbname, const char *username)
 				 username, InvalidOid,	/* role to connect as */
 				 !am_walsender, /* honor session_preload_libraries? */
 				 false,			/* don't ignore datallowconn */
-				 NULL,			/* no out_dbname */
-				 NULL);			/* session id */
+				 NULL			/* no out_dbname */ );
 
 	/*
 	 * If the PostmasterContext is still around, recycle the space; we don't

src/postgres/src/backend/utils/init/postinit.c

@@ -110,14 +110,6 @@ static void process_startup_options(Port *port, bool am_superuser);
 static void process_settings(Oid databaseid, Oid roleid);
 
 /* YB functions */
-static void InitPostgresImpl(const char *in_dbname, Oid dboid,
-							 const char *username, Oid useroid,
-							 bool load_session_libraries,
-							 bool override_allow_connections,
-							 char *out_dbname,
-							 uint64_t *yb_session_id,
-							 bool *yb_sys_table_prefetching_started);
-static void YbEnsureSysTablePrefetchingStopped();
 static void YbPresetDatabaseCollation(HeapTuple tuple);
 
 /*** InitPostgres support ***/
@@ -725,25 +717,10 @@ InitPostgres(const char *in_dbname, Oid dboid,
 			 const char *username, Oid useroid,
 			 bool load_session_libraries,
 			 bool override_allow_connections,
-			 char *out_dbname,
-			 uint64_t *yb_session_id)
+			 char *out_dbname)
 {
-	bool		sys_table_prefetching_started = false;
-
-	PG_TRY();
-	{
-		InitPostgresImpl(in_dbname, dboid, username, useroid,
-						 load_session_libraries, override_allow_connections,
-						 out_dbname, yb_session_id,
-						 &sys_table_prefetching_started);
-	}
-	PG_CATCH();
-	{
-		YbEnsureSysTablePrefetchingStopped();
-		PG_RE_THROW();
-	}
-	PG_END_TRY();
-	YbEnsureSysTablePrefetchingStopped();
+	YbInitPostgres(in_dbname, dboid, username, useroid, load_session_libraries,
+				   override_allow_connections, out_dbname, NULL);
 }
 
 static void
@@ -752,7 +729,7 @@ InitPostgresImpl(const char *in_dbname, Oid dboid,
 				 bool load_session_libraries,
 				 bool override_allow_connections,
 				 char *out_dbname,
-				 uint64_t *yb_session_id,
+				 const YbcPgInitPostgresInfo *yb_init_info,
 				 bool *yb_sys_table_prefetching_started)
 {
 	bool		bootstrap = IsBootstrapProcessingMode();
@@ -861,10 +838,7 @@ InitPostgresImpl(const char *in_dbname, Oid dboid,
 		YbAshSetOneTimeMetadata();
 
 	/* Connect to YugaByte cluster. */
-	if (bootstrap)
-		YBInitPostgresBackend("postgres", yb_session_id);
-	else
-		YBInitPostgresBackend("postgres", yb_session_id);
+	YBInitPostgresBackend("postgres", yb_init_info);
 
 	if (IsYugaByteEnabled() && !bootstrap)
 	{
@@ -1439,6 +1413,30 @@ YbEnsureSysTablePrefetchingStopped()
 		YBCStopSysTablePrefetching();
 }
 
+void
+YbInitPostgres(const char *in_dbname, Oid dboid,
+			 const char *username, Oid useroid,
+			 bool load_session_libraries,
+			 bool override_allow_connections,
+			 char *out_dbname, const YbcPgInitPostgresInfo *yb_init_info)
+{
+	bool sys_table_prefetching_started = false;
+
+	PG_TRY();
+	{
+		InitPostgresImpl(in_dbname, dboid, username, useroid,
+						 load_session_libraries, override_allow_connections,
+						 out_dbname, yb_init_info, &sys_table_prefetching_started);
+	}
+	PG_CATCH();
+	{
+		YbEnsureSysTablePrefetchingStopped();
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+	YbEnsureSysTablePrefetchingStopped();
+}
+
 /*
  * Check and set database collation once MyDatabaseId is resolved. In YB we
  * need to do this earlier because of prefetching where we may need to

src/postgres/src/backend/utils/misc/pg_yb_utils.c

@@ -1098,7 +1098,7 @@ IpAddressToBytes(YbcPgAshConfig *ash_config)
 }
 
 void
-YBInitPostgresBackend(const char *program_name, uint64_t *session_id)
+YBInitPostgresBackend(const char *program_name, const YbcPgInitPostgresInfo *init_info)
 {
 	HandleYBStatus(YBCInit(program_name, palloc, cstring_to_text_with_len));
 
@@ -1124,7 +1124,12 @@ YBInitPostgresBackend(const char *program_name, uint64_t *session_id)
 		ash_config.metadata = &MyProc->yb_ash_metadata;
 
 		IpAddressToBytes(&ash_config);
-		YBCInitPgGate(YbGetTypeTable(), &callbacks, session_id, &ash_config);
+		const YbcPgInitPostgresInfo default_init_info = {
+			.parallel_leader_session_id = NULL,
+			.shared_data = &MyProc->yb_shared_data
+		};
+		YBCInitPgGate(YbGetTypeTable(), &callbacks,
+					init_info ? init_info : &default_init_info, &ash_config);
 		YBCInstallTxnDdlHook();
 
 		/*

src/postgres/src/include/miscadmin.h

@@ -32,7 +32,7 @@
 #ifndef FRONTEND
 #include "storage/proc.h"		/* for MyProc */
 #endif
-
+#include "yb/yql/pggate/ybc_pg_typedefs.h"
 
 #define InvalidPid				(-1)
 
@@ -488,11 +488,18 @@ extern PGDLLIMPORT AuxProcType MyAuxProcType;
 extern void pg_split_opts(char **argv, int *argcp, const char *optstr);
 extern void InitializeMaxBackends(void);
 extern void InitPostgres(const char *in_dbname, Oid dboid,
+						 const char *username, Oid useroid,
+						 bool load_session_libraries,
+						 bool override_allow_connections,
+						 char *out_dbname);
+
+extern void YbInitPostgres(const char *in_dbname, Oid dboid,
 						 const char *username, Oid useroid,
 						 bool load_session_libraries,
 						 bool override_allow_connections,
 						 char *out_dbname,
-						 uint64_t *yb_session_id);
+						 const YbcPgInitPostgresInfo *yb_info);
+
 extern void BaseInit(void);
 
 /* in utils/init/miscinit.c */