commit 753c46352adc967a903a60ea65a3068252d685e6
Author: Jacob Champion <jchampion@timescale.com>
Date:   Tue Aug 16 09:14:58 2022 -0700

    squash! Allow parallel workers to read authn_id
    
    Per review,
    - add an intermediate struct for serialization,
    - switch to length-prefixing for the authn_id string, and
    - make sure `struct ClientConnectionInfo` is declared for use elsewhere.

diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index 155ba92c67..58772d0a4a 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -943,19 +943,29 @@ GetUserNameFromId(Oid roleid, bool noerr)
 
 ClientConnectionInfo MyClientConnectionInfo;
 
+/*
+ * Intermediate representation of ClientConnectionInfo for easier serialization.
+ * Variable-length fields are allocated right after this header.
+ */
+typedef struct SerializedClientConnectionInfo
+{
+	int32		authn_id_len; /* strlen(authn_id), or -1 if NULL */
+	UserAuth	auth_method;
+} SerializedClientConnectionInfo;
+
 /*
  * Calculate the space needed to serialize MyClientConnectionInfo.
  */
 Size
 EstimateClientConnectionInfoSpace(void)
 {
-	Size		size = 1;
+	Size		size = 0;
+
+	size = add_size(size, sizeof(SerializedClientConnectionInfo));
 
 	if (MyClientConnectionInfo.authn_id)
 		size = add_size(size, strlen(MyClientConnectionInfo.authn_id) + 1);
 
-	size = add_size(size, sizeof(UserAuth));
-
 	return size;
 }
 
@@ -965,32 +975,29 @@ EstimateClientConnectionInfoSpace(void)
 void
 SerializeClientConnectionInfo(Size maxsize, char *start_address)
 {
-	/*
-	 * First byte is an indication of whether or not authn_id has been set to
-	 * non-NULL, to differentiate that case from the empty string.
-	 */
-	Assert(maxsize > 0);
-	start_address[0] = MyClientConnectionInfo.authn_id ? 1 : 0;
-	start_address++;
-	maxsize--;
+	SerializedClientConnectionInfo serialized = {0};
+
+	serialized.authn_id_len = -1;
+	serialized.auth_method = MyClientConnectionInfo.auth_method;
 
 	if (MyClientConnectionInfo.authn_id)
-	{
-		Size len;
+		serialized.authn_id_len = strlen(MyClientConnectionInfo.authn_id);
 
-		len = strlcpy(start_address, MyClientConnectionInfo.authn_id, maxsize) + 1;
-		Assert(len <= maxsize);
-		maxsize -= len;
-		start_address += len;
-	}
+	/* Copy serialized representation to buffer */
+	Assert(maxsize >= sizeof(serialized));
+	memcpy(start_address, &serialized, sizeof(serialized));
 
-	{
-		UserAuth	   *auth_method = (UserAuth*) start_address;
+	maxsize -= sizeof(serialized);
+	start_address += sizeof(serialized);
 
-		Assert(sizeof(*auth_method) <= maxsize);
-		*auth_method = MyClientConnectionInfo.auth_method;
-		maxsize -= sizeof(*auth_method);
-		start_address += sizeof(*auth_method);
+	/* Copy authn_id into the space after the struct. */
+	if (serialized.authn_id_len >= 0)
+	{
+		Assert(maxsize >= (serialized.authn_id_len + 1));
+		memcpy(start_address,
+			   MyClientConnectionInfo.authn_id,
+			   /* include the NULL terminator to ease deserialization */
+			   serialized.authn_id_len + 1);
 	}
 }
 
@@ -1000,25 +1007,19 @@ SerializeClientConnectionInfo(Size maxsize, char *start_address)
 void
 RestoreClientConnectionInfo(char *conninfo)
 {
-	if (conninfo[0] == 0)
-	{
-		MyClientConnectionInfo.authn_id = NULL;
-		conninfo++;
-	}
-	else
-	{
-		conninfo++;
-		MyClientConnectionInfo.authn_id = MemoryContextStrdup(TopMemoryContext,
-															  conninfo);
-		conninfo += strlen(conninfo) + 1;
-	}
+	SerializedClientConnectionInfo serialized;
+	char	   *authn_id;
 
-	{
-		UserAuth	   *auth_method = (UserAuth*) conninfo;
+	memcpy(&serialized, conninfo, sizeof(serialized));
+	authn_id = conninfo + sizeof(serialized);
 
-		MyClientConnectionInfo.auth_method = *auth_method;
-		conninfo += sizeof(*auth_method);
-	}
+	/* Copy the fields back into place. */
+	MyClientConnectionInfo.authn_id = NULL;
+	MyClientConnectionInfo.auth_method = serialized.auth_method;
+
+	if (serialized.authn_id_len >= 0)
+		MyClientConnectionInfo.authn_id = MemoryContextStrdup(TopMemoryContext,
+															  authn_id);
 }
 
 
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 0643733765..84a6bdea6f 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -107,7 +107,7 @@ typedef struct
  * If you add a struct member here, remember to also handle serialization in
  * SerializeClientConnectionInfo() et al.
  */
-typedef struct
+typedef struct ClientConnectionInfo
 {
 	/*
 	 * Authenticated identity.  The meaning of this identifier is dependent on