Allow parallel workers to retrieve some data from Port

This commit moves authn_id into a new global structure called
ClientConnectionInfo (mapping to a MyClientConnectionInfo for each
backend) which is intended to hold all the client information that
should be shared between the backend and any of its parallel workers,
access for extensions and triggers being the primary use case.  There is
no need to push all the data of Port to the workers, and authn_id is
quite a generic concept so using a separate structure provides the best
balance (the name of the structure has been suggested by Robert Haas).

While on it, and per discussion as this would be useful for a potential
SYSTEM_USER that can be accessed through parallel workers, a second
field is added for the authentication method, copied directly from
Port.

ClientConnectionInfo is serialized and restored using a new parallel
key and a structure tracks the length of the authn_id, making the
addition of more fields straight-forward.

Author: Jacob Champion
Reviewed-by: Bertrand Drouvot, Stephen Frost, Robert Haas, Tom Lane,
Michael Paquier, Julien Rouhaud
Discussion: https://postgr.es/m/793d990837ae5c06a558d58d62de9378ab525d83.camel@vmware.com

1 files changed, 18 insertions, 1 deletions

diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index df0cd775588..bc93101ff71 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -76,6 +76,7 @@
 #define PARALLEL_KEY_REINDEX_STATE			UINT64CONST(0xFFFFFFFFFFFF000C)
 #define PARALLEL_KEY_RELMAPPER_STATE		UINT64CONST(0xFFFFFFFFFFFF000D)
 #define PARALLEL_KEY_UNCOMMITTEDENUMS		UINT64CONST(0xFFFFFFFFFFFF000E)
+#define PARALLEL_KEY_CLIENTCONNINFO			UINT64CONST(0xFFFFFFFFFFFF000F)
 
 /* Fixed-size parallel state. */
 typedef struct FixedParallelState
@@ -212,6 +213,7 @@ InitializeParallelDSM(ParallelContext *pcxt)
 	Size		reindexlen = 0;
 	Size		relmapperlen = 0;
 	Size		uncommittedenumslen = 0;
+	Size		clientconninfolen = 0;
 	Size		segsize = 0;
 	int			i;
 	FixedParallelState *fps;
@@ -272,8 +274,10 @@ InitializeParallelDSM(ParallelContext *pcxt)
 		shm_toc_estimate_chunk(&pcxt->estimator, relmapperlen);
 		uncommittedenumslen = EstimateUncommittedEnumsSpace();
 		shm_toc_estimate_chunk(&pcxt->estimator, uncommittedenumslen);
+		clientconninfolen = EstimateClientConnectionInfoSpace();
+		shm_toc_estimate_chunk(&pcxt->estimator, clientconninfolen);
 		/* If you add more chunks here, you probably need to add keys. */
-		shm_toc_estimate_keys(&pcxt->estimator, 11);
+		shm_toc_estimate_keys(&pcxt->estimator, 12);
 
 		/* Estimate space need for error queues. */
 		StaticAssertStmt(BUFFERALIGN(PARALLEL_ERROR_QUEUE_SIZE) ==
@@ -352,6 +356,7 @@ InitializeParallelDSM(ParallelContext *pcxt)
 		char	   *session_dsm_handle_space;
 		char	   *entrypointstate;
 		char	   *uncommittedenumsspace;
+		char	   *clientconninfospace;
 		Size		lnamelen;
 
 		/* Serialize shared libraries we have loaded. */
@@ -422,6 +427,12 @@ InitializeParallelDSM(ParallelContext *pcxt)
 		shm_toc_insert(pcxt->toc, PARALLEL_KEY_UNCOMMITTEDENUMS,
 					   uncommittedenumsspace);
 
+		/* Serialize our ClientConnectionInfo. */
+		clientconninfospace = shm_toc_allocate(pcxt->toc, clientconninfolen);
+		SerializeClientConnectionInfo(clientconninfolen, clientconninfospace);
+		shm_toc_insert(pcxt->toc, PARALLEL_KEY_CLIENTCONNINFO,
+					   clientconninfospace);
+
 		/* Allocate space for worker information. */
 		pcxt->worker = palloc0(sizeof(ParallelWorkerInfo) * pcxt->nworkers);
 
@@ -1270,6 +1281,7 @@ ParallelWorkerMain(Datum main_arg)
 	char	   *reindexspace;
 	char	   *relmapperspace;
 	char	   *uncommittedenumsspace;
+	char	   *clientconninfospace;
 	StringInfoData msgbuf;
 	char	   *session_dsm_handle_space;
 	Snapshot	tsnapshot;
@@ -1479,6 +1491,11 @@ ParallelWorkerMain(Datum main_arg)
 										   false);
 	RestoreUncommittedEnums(uncommittedenumsspace);
 
+	/* Restore the ClientConnectionInfo. */
+	clientconninfospace = shm_toc_lookup(toc, PARALLEL_KEY_CLIENTCONNINFO,
+										 false);
+	RestoreClientConnectionInfo(clientconninfospace);
+
 	/* Attach to the leader's serializable transaction, if SERIALIZABLE. */
 	AttachSerializableXact(fps->serializable_xact_handle);