Create an infrastructure for parallel computation in PostgreSQL.

This does four basic things.  First, it provides convenience routines
to coordinate the startup and shutdown of parallel workers.  Second,
it synchronizes various pieces of state (e.g. GUCs, combo CID
mappings, transaction snapshot) from the parallel group leader to the
worker processes.  Third, it prohibits various operations that would
result in unsafe changes to that state while parallelism is active.
Finally, it propagates events that would result in an ErrorResponse,
NoticeResponse, or NotifyResponse message being sent to the client
from the parallel workers back to the master, from which they can then
be sent on to the client.

Robert Haas, Amit Kapila, Noah Misch, Rushabh Lathia, Jeevan Chalke.
Suggestions and review from Andres Freund, Heikki Linnakangas, Noah
Misch, Simon Riggs, Euler Taveira, and Jim Nasby.

1 files changed, 54 insertions, 0 deletions

diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c
index 7476a26b791..46bc1f238f2 100644
--- a/src/backend/utils/fmgr/dfmgr.c
+++ b/src/backend/utils/fmgr/dfmgr.c
@@ -23,6 +23,7 @@
 #endif
 #include "lib/stringinfo.h"
 #include "miscadmin.h"
+#include "storage/shmem.h"
 #include "utils/dynamic_loader.h"
 #include "utils/hsearch.h"
 
@@ -692,3 +693,56 @@ find_rendezvous_variable(const char *varName)
 
 	return &hentry->varValue;
 }
+
+/*
+ * Estimate the amount of space needed to serialize the list of libraries
+ * we have loaded.
+ */
+Size
+EstimateLibraryStateSpace(void)
+{
+	DynamicFileList *file_scanner;
+	Size	size = 1;
+
+	for (file_scanner = file_list;
+		 file_scanner != NULL;
+		 file_scanner = file_scanner->next)
+		size = add_size(size, strlen(file_scanner->filename) + 1);
+
+	return size;
+}
+
+/*
+ * Serialize the list of libraries we have loaded to a chunk of memory.
+ */
+void
+SerializeLibraryState(Size maxsize, char *start_address)
+{
+	DynamicFileList *file_scanner;
+
+	for (file_scanner = file_list;
+		 file_scanner != NULL;
+		 file_scanner = file_scanner->next)
+	{
+		Size len;
+
+		len = strlcpy(start_address, file_scanner->filename, maxsize) + 1;
+		Assert(len < maxsize);
+		maxsize -= len;
+		start_address += len;
+	}
+	start_address[0] = '\0';
+}
+
+/*
+ * Load every library the serializing backend had loaded.
+ */
+void
+RestoreLibraryState(char *start_address)
+{
+	while (*start_address != '\0')
+	{
+		internal_load_library(start_address);
+		start_address += strlen(start_address) + 1;
+	}
+}