From 3af09535162d35772b510f6dfd2912dfad73e4b1 Mon Sep 17 00:00:00 2001
From: Bernd Verst <4535280+berndverst@users.noreply.github.com>
Date: Wed, 16 Nov 2022 19:59:22 -0800
Subject: [PATCH] Postgres State Store: Add Support for First-Write concurrency

Signed-off-by: Bernd Verst <4535280+berndverst@users.noreply.github.com>
---
 state/postgresql/postgresdbaccess.go | 6 +++++-
 tests/config/state/tests.yml         | 4 ++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/state/postgresql/postgresdbaccess.go b/state/postgresql/postgresdbaccess.go
index 8ffa628d9..3e62985a2 100644
--- a/state/postgresql/postgresdbaccess.go
+++ b/state/postgresql/postgresdbaccess.go
@@ -143,7 +143,11 @@ func (p *postgresDBAccess) setValue(req *state.SetRequest) error {
 
 	// Sprintf is required for table name because sql.DB does not substitute parameters for table names.
 	// Other parameters use sql.DB parameter substitution.
-	if req.ETag == nil {
+	if req.Options.Concurrency == state.FirstWrite && (req.ETag == nil || *req.ETag == "") {
+		result, err = p.db.Exec(fmt.Sprintf(
+			`INSERT INTO %s (key, value, isbinary) VALUES ($1, $2, $3);`,
+			defaultTableName), req.Key, value, isBinary)
+	} else if req.ETag == nil {
 		result, err = p.db.Exec(fmt.Sprintf(
 			`INSERT INTO %s (key, value, isbinary) VALUES ($1, $2, $3)
 			ON CONFLICT (key) DO UPDATE SET value = $2, isbinary = $3, updatedate = NOW();`,
diff --git a/tests/config/state/tests.yml b/tests/config/state/tests.yml
index e3215c940..d211c5021 100644
--- a/tests/config/state/tests.yml
+++ b/tests/config/state/tests.yml
@@ -21,7 +21,7 @@ components:
     operations: [ "set", "get", "delete", "bulkset", "bulkdelete", "transaction", "etag", "first-write" ]
   - component: postgresql
     allOperations: false
-    operations: [ "set", "get", "delete", "bulkset", "bulkdelete", "transaction", "etag", "query" ]
+    operations: [ "set", "get", "delete", "bulkset", "bulkdelete", "transaction", "etag", "query", "first-write" ]
   - component: mysql.mysql
     allOperations: false
     operations: [ "set", "get", "delete", "bulkset", "bulkdelete", "transaction", "etag",  "first-write" ]
@@ -42,4 +42,4 @@ components:
     operations: [ "set", "get", "delete", "bulkset", "bulkdelete", "transaction", "etag", "query" ]
   - component: rethinkdb
     allOperations: false
-    operations: [ "set", "get", "delete", "bulkset", "bulkdelete"]
\ No newline at end of file
+    operations: [ "set", "get", "delete", "bulkset", "bulkdelete"]