Move hid generation to the database. Closes #157.

PluralKit.Core/Database/Functions/functions.sql

@@ -81,4 +81,31 @@ as $$
         inner join members on members.system = systems.id
         left join member_guild on member_guild.member = members.id and member_guild.guild = guild_id
     where accounts.uid = account_id
-$$ language sql stable rows 10;
+$$ language sql stable rows 10;
+
+
+create function generate_hid() returns text as $$
+    select string_agg(substr('abcdefghijklmnopqrstuvwxyz', ceil(random() * 26)::integer, 1), '') from generate_series(1, 5)
+$$ language sql volatile;
+
+
+create function find_free_system_hid() returns text as $$
+declare new_hid text;
+begin
+    loop
+        new_hid := generate_hid();
+        if not exists (select 1 from systems where hid = new_hid) then return new_hid; end if;
+    end loop;
+end
+$$ language plpgsql volatile;
+
+
+create function find_free_member_hid() returns text as $$
+declare new_hid text;
+begin
+    loop
+        new_hid := generate_hid();
+        if not exists (select 1 from members where hid = new_hid) then return new_hid; end if;
+    end loop;
+end
+$$ language plpgsql volatile;

PluralKit.Core/Database/clean.sql

@@ -2,4 +2,7 @@
 drop view if exists member_list;
 
 drop function if exists message_context;
-drop function if exists proxy_members;
+drop function if exists proxy_members;
+drop function if exists generate_hid;
+drop function if exists find_free_system_hid;
+drop function if exists find_free_member_hid;

PluralKit.Core/Services/PostgresDataStore.cs

@@ -58,15 +58,9 @@ namespace PluralKit.Core {
         }
 
         public async Task<PKSystem> CreateSystem(string systemName = null) {
-            string hid;
-            do
-            {
-                hid = StringUtils.GenerateHid();
-            } while (await GetSystemByHid(hid) != null);
-
             PKSystem system;
             using (var conn = await _conn.Obtain())
-                system = await conn.QuerySingleAsync<PKSystem>("insert into systems (hid, name) values (@Hid, @Name) returning *", new { Hid = hid, Name = systemName });
+                system = await conn.QuerySingleAsync<PKSystem>("insert into systems (hid, name) values (find_free_system_hid(), @Name) returning *", new { Name = systemName });
 
             _logger.Information("Created system {System}", system.Id);
             // New system has no accounts, therefore nothing gets cached, therefore no need to invalidate caches right here
@@ -147,16 +141,9 @@ namespace PluralKit.Core {
         }
 
         public async Task<PKMember> CreateMember(PKSystem system, string name) {
-            string hid;
-            do
-            {
-                hid = StringUtils.GenerateHid();
-            } while (await GetMemberByHid(hid) != null);
-
             PKMember member;
             using (var conn = await _conn.Obtain())
-                member = await conn.QuerySingleAsync<PKMember>("insert into members (hid, system, name) values (@Hid, @SystemId, @Name) returning *", new {
-                    Hid = hid,
+                member = await conn.QuerySingleAsync<PKMember>("insert into members (hid, system, name) values (find_free_member_hid(), @SystemId, @Name) returning *", new {
                     SystemID = system.Id,
                     Name = name
                 });

PluralKit.Core/Utils/BulkImporter.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Data;
 using System.Linq;
 using System.Threading.Tasks;
 
@@ -69,7 +70,7 @@ namespace PluralKit.Core
             // if not, roll a new hid and we'll insert one with that
             // (we can't trust the hid given in the member, it might let us overwrite another system's members)
             var existingMember = FindExistingMemberInSystem(member.Hid, member.Name); 
-            string newHid = existingMember?.Hid ?? await FindFreeHid();
+            string newHid = existingMember?.Hid ?? await _conn.QuerySingleAsync<string>("find_free_member_hid", commandType: CommandType.StoredProcedure);
 
             // Upsert member data and return the ID
             QueryBuilder qb = QueryBuilder.Upsert("members", "hid")
@@ -112,19 +113,6 @@ namespace PluralKit.Core
             return null;
         }
 
-        private async Task<string> FindFreeHid()
-        {
-            string hid;
-            do
-            {
-                hid = await _conn.QuerySingleOrDefaultAsync<string>(
-                    "select @Hid where not exists (select id from members where hid = @Hid)",
-                    new {Hid = StringUtils.GenerateHid()});
-            } while (hid == null);
-
-            return hid;
-        }
-
         /// <summary>
         /// Register switches in bulk.
         /// </summary>

PluralKit.Core/Utils/StringUtils.cs

@@ -6,18 +6,6 @@ namespace PluralKit.Core
 {
     public static class StringUtils
     {
-        public static string GenerateHid()
-        {
-            var rnd = new Random();
-            var charset = "abcdefghijklmnopqrstuvwxyz";
-            string hid = "";
-            for (int i = 0; i < 5; i++)
-            {
-                hid += charset[rnd.Next(charset.Length)];
-            }
-            return hid;
-        }
-
         public static string GenerateToken()
         {
             var buf = new byte[48]; // Results in a 64-byte Base64 string (no padding)