Changeset 0496e6e for iknow-api/Services/Implementations/EnrollmentService.cs

Timestamp:

09/23/26 13:29:17 (11 hours ago)

Author:

Stefan-Saveski <stefansaveski19@…>

Branches:

master

Children:

2853f2e

Parents:

e7bafc0 (diff), 002cf5f (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge remote-tracking branch 'origin/phase8-transactions-pooling'

File:

• iknow-api/Services/Implementations/EnrollmentService.cs (modified) (3 diffs)

iknow-api/Services/Implementations/EnrollmentService.cs

@@ -3 +3 @@
 using iknow_api.Models;
 using Microsoft.EntityFrameworkCore;
+using Npgsql;
 
 namespace iknow_api.Services
@@ -220 +221 @@
                 };
             }
+            catch (DbUpdateException ex) when (IsUniqueViolation(ex))
+            {
+                // Two enrolments for the same semester sent at the same time both
+                // pass the check above, because each transaction reads the state
+                // from before the other one wrote. UNIQUE (user_id, semester_id)
+                // is what actually settles it, so the loser gets the same
+                // sentence as if the check had caught it.
+                await transaction.RollbackAsync();
+                return Fail("You are already enrolled in that semester.");
+            }
             catch
             {
@@ -226 +237 @@
             }
         }
+
+        /// <summary>23505 is unique_violation.</summary>
+        private static bool IsUniqueViolation(DbUpdateException ex) =>
+            ex.InnerException is PostgresException { SqlState: "23505" };
 
         private static EnrollSemesterResultDto Fail(string message) =>