docs: Handle conflicts on customized session attribute queries

Author: ro-vn

spring-session-docs/modules/ROOT/pages/configuration/jdbc.adoc

@@ -155,13 +155,13 @@ public class QueryCustomizer
     private static final String CREATE_SESSION_ATTRIBUTE_QUERY = """
             INSERT INTO %TABLE_NAME%_ATTRIBUTES (SESSION_PRIMARY_ID, ATTRIBUTE_NAME, ATTRIBUTE_BYTES) <1>
             VALUES (?, ?, ?)
-            ON CONFLICT (SESSION_PRIMARY_ID, ATTRIBUTE_NAME)
-            DO NOTHING
+            ON CONFLICT (SESSION_PRIMARY_ID, ATTRIBUTE_NAME) <2>
+            DO UPDATE SET ATTRIBUTE_BYTES = EXCLUDED.ATTRIBUTE_BYTES
             """;
 
     private static final String UPDATE_SESSION_ATTRIBUTE_QUERY = """
 		UPDATE %TABLE_NAME%_ATTRIBUTES
-		SET ATTRIBUTE_BYTES = convert_from(?, 'UTF8')::jsonb
+		SET ATTRIBUTE_BYTES = encode(?, 'escape')
 		WHERE SESSION_PRIMARY_ID = ?
 		AND ATTRIBUTE_NAME = ?
 		""";
@@ -177,6 +177,7 @@ public class QueryCustomizer
 ======
 
 <1> The `%TABLE_NAME%` placeholder in the query will be replaced by the configured table name being used by `JdbcIndexedSessionRepository`.
+<2> `ON CONFLICT` handles duplicate keys by updating the existing row instead of throwing an error, making the insert operation idempotent.
 
 [TIP]
 ====
@@ -310,6 +311,8 @@ public class SessionConfig {
     private static final String CREATE_SESSION_ATTRIBUTE_QUERY = """
             INSERT INTO %TABLE_NAME%_ATTRIBUTES (SESSION_PRIMARY_ID, ATTRIBUTE_NAME, ATTRIBUTE_BYTES)
             VALUES (?, ?, convert_from(?, 'UTF8')::jsonb) <1>
+            ON CONFLICT (SESSION_PRIMARY_ID, ATTRIBUTE_NAME)
+            DO UPDATE SET ATTRIBUTE_BYTES = EXCLUDED.ATTRIBUTE_BYTES
             """;
 
     private static final String UPDATE_SESSION_ATTRIBUTE_QUERY = """
@@ -331,7 +334,7 @@ public class SessionConfig {
 ----
 ======
 
-<1> Uses the https://www.postgresql.org/docs/current/functions-binarystring.html[PostgreSQL encode] function to convert from `bytea` to `text`
+<1> Uses the https://www.postgresql.org/docs/current/functions-binarystring.html[PostgreSQL convert_from] function to convert the `bytea` value to `text`, which is then cast to `jsonb`.
 
 And that's it, you should now be able to see the session attributes saved as JSON in the database.
 There is a https://github.com/spring-projects/spring-session/tree/main/spring-session-samples/spring-session-sample-boot-jdbc-json-attribute[sample available] where you can see the whole implementation and run the tests.

spring-session-samples/spring-session-sample-boot-jdbc-json-attribute/src/main/java/sample/config/SessionConfig.java

@@ -24,11 +24,13 @@ public class SessionConfig implements BeanClassLoaderAware {
 	private static final String CREATE_SESSION_ATTRIBUTE_QUERY = """
 			INSERT INTO %TABLE_NAME%_ATTRIBUTES (SESSION_PRIMARY_ID, ATTRIBUTE_NAME, ATTRIBUTE_BYTES)
 			VALUES (?, ?, convert_from(?, 'UTF8')::jsonb)
+			ON CONFLICT (SESSION_PRIMARY_ID, ATTRIBUTE_NAME)
+			DO UPDATE SET ATTRIBUTE_BYTES = EXCLUDED.ATTRIBUTE_BYTES
 			""";
 
 	private static final String UPDATE_SESSION_ATTRIBUTE_QUERY = """
 			UPDATE %TABLE_NAME%_ATTRIBUTES
-			SET ATTRIBUTE_BYTES = encode(?, 'escape')::jsonb
+			SET ATTRIBUTE_BYTES = convert_from(?, 'UTF8')::jsonb
 			WHERE SESSION_PRIMARY_ID = ?
 			AND ATTRIBUTE_NAME = ?
 			""";