fix(plugin-server): fix conflict case in addPersonlessDistinctId

plugin-server/src/utils/db/db.ts

@@ -862,7 +862,23 @@ export class DB {
             'addPersonlessDistinctId'
         )
 
-        return result.rows[0]['is_merged']
+        if (result.rows.length === 1) {
+            return result.rows[0]['is_merged']
+        }
+
+        // ON CONFLICT ... DO NOTHING won't give us our RETURNING, so we have to do another SELECT
+        const existingResult = await this.postgres.query(
+            PostgresUse.COMMON_WRITE,
+            `
+                SELECT is_merged
+                FROM posthog_personlessdistinctid
+                WHERE team_id = $1 AND distinct_id = $2
+            `,
+            [teamId, distinctId],
+            'addPersonlessDistinctId'
+        )
+
+        return existingResult.rows[0]['is_merged']
     }
 
     public async addPersonlessDistinctIdForMerge(

plugin-server/tests/main/db.test.ts

@@ -284,6 +284,23 @@ describe('DB', () => {
         return selectResult.rows[0]
     }
 
+    test('addPersonlessDistinctId', async () => {
+        const team = await getFirstTeam(hub)
+        await db.addPersonlessDistinctId(team.id, 'addPersonlessDistinctId')
+
+        // This will conflict, but shouldn't throw an error
+        await db.addPersonlessDistinctId(team.id, 'addPersonlessDistinctId')
+
+        const result = await db.postgres.query(
+            PostgresUse.COMMON_WRITE,
+            'SELECT id FROM posthog_personlessdistinctid WHERE team_id = $1 AND distinct_id = $2',
+            [team.id, 'addPersonlessDistinctId'],
+            'addPersonlessDistinctId'
+        )
+
+        expect(result.rows.length).toEqual(1)
+    })
+
     describe('createPerson', () => {
         let team: Team
         const uuid = new UUIDT().toString()