Make sure (most) queries avoid table scans.

I've exempted inserts (they never scan in the first place), queries on `event_sequence` (at most one row), and the coalesce()s used for event replay (for now; these are obviously a performance risk area and need addressing).

Method:

```
find .sqlx -name 'query-*.json' -exec jq -r '"explain query plan " + .query + ";"' {} + > explain.sql
```

Then go query by query through the resulting file.

10 files changed, 144 insertions, 160 deletions

diff --git a/.sqlx/query-10a8d7ebb8a228c297f38e8ec70ecce6408cb241c9ac5f76bb484b214e720cb9.json b/.sqlx/query-10a8d7ebb8a228c297f38e8ec70ecce6408cb241c9ac5f76bb484b214e720cb9.json
deleted file mode 100644
index f8dd228..0000000
--- a/.sqlx/query-10a8d7ebb8a228c297f38e8ec70ecce6408cb241c9ac5f76bb484b214e720cb9.json
+++ /dev/null
@@ -1,56 +0,0 @@
-{
-  "db_name": "SQLite",
-  "query": "\n                select\n                    channel.id as \"id: Id\",\n                    name.display_name as \"display_name: String\",\n                    name.canonical_name as \"canonical_name: String\",\n                    channel.created_at as \"created_at: DateTime\",\n                    channel.created_sequence as \"created_sequence: Sequence\",\n                    deleted.deleted_at as \"deleted_at?: DateTime\",\n                    deleted.deleted_sequence as \"deleted_sequence?: Sequence\"\n                from channel\n                left join channel_name as name\n                    using (id)\n                left join channel_deleted as deleted\n                    using (id)\n                left join message\n                    on channel.id = message.channel\n                where channel.created_at < $1\n                    and message.id is null\n                    and deleted.id is null\n            ",
-  "describe": {
-    "columns": [
-      {
-        "name": "id: Id",
-        "ordinal": 0,
-        "type_info": "Text"
-      },
-      {
-        "name": "display_name: String",
-        "ordinal": 1,
-        "type_info": "Null"
-      },
-      {
-        "name": "canonical_name: String",
-        "ordinal": 2,
-        "type_info": "Null"
-      },
-      {
-        "name": "created_at: DateTime",
-        "ordinal": 3,
-        "type_info": "Text"
-      },
-      {
-        "name": "created_sequence: Sequence",
-        "ordinal": 4,
-        "type_info": "Integer"
-      },
-      {
-        "name": "deleted_at?: DateTime",
-        "ordinal": 5,
-        "type_info": "Text"
-      },
-      {
-        "name": "deleted_sequence?: Sequence",
-        "ordinal": 6,
-        "type_info": "Integer"
-      }
-    ],
-    "parameters": {
-      "Right": 1
-    },
-    "nullable": [
-      false,
-      true,
-      true,
-      false,
-      false,
-      true,
-      true
-    ]
-  },
-  "hash": "10a8d7ebb8a228c297f38e8ec70ecce6408cb241c9ac5f76bb484b214e720cb9"
-}
diff --git a/.sqlx/query-15ec7a8aa11908f8b2022accdde2e9e4a49e52e74c3d0e28e82a0b01a3c9887f.json b/.sqlx/query-15ec7a8aa11908f8b2022accdde2e9e4a49e52e74c3d0e28e82a0b01a3c9887f.json
deleted file mode 100644
index 167e768..0000000
--- a/.sqlx/query-15ec7a8aa11908f8b2022accdde2e9e4a49e52e74c3d0e28e82a0b01a3c9887f.json
+++ /dev/null
@@ -1,20 +0,0 @@
-{
-  "db_name": "SQLite",
-  "query": "\n                insert into message_deleted (id, deleted_at, deleted_sequence)\n                values ($1, $2, $3)\n                returning 1 as \"deleted: bool\"\n            ",
-  "describe": {
-    "columns": [
-      {
-        "name": "deleted: bool",
-        "ordinal": 0,
-        "type_info": "Null"
-      }
-    ],
-    "parameters": {
-      "Right": 3
-    },
-    "nullable": [
-      null
-    ]
-  },
-  "hash": "15ec7a8aa11908f8b2022accdde2e9e4a49e52e74c3d0e28e82a0b01a3c9887f"
-}
diff --git a/.sqlx/query-2f26bccedd1226764e49f00a94e43226ee6aebdd14d7be97a708d66263a30abf.json b/.sqlx/query-2f26bccedd1226764e49f00a94e43226ee6aebdd14d7be97a708d66263a30abf.json
new file mode 100644
index 0000000..686afb9
--- /dev/null
+++ b/.sqlx/query-2f26bccedd1226764e49f00a94e43226ee6aebdd14d7be97a708d66263a30abf.json
@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "\n                insert into message_deleted (id, deleted_at, deleted_sequence)\n                values ($1, $2, $3)\n            ",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 3
+    },
+    "nullable": []
+  },
+  "hash": "2f26bccedd1226764e49f00a94e43226ee6aebdd14d7be97a708d66263a30abf"
+}
diff --git a/.sqlx/query-40e0310af2814435cca882701b86eddb5a1114202ba385f66f131b1601feec11.json b/.sqlx/query-4623f989492e9eae6788ee9472f1138395b50cdfc9a28e9791e5484890f0201b.json
index 3147d7f..bfab6d4 100644
--- a/.sqlx/query-40e0310af2814435cca882701b86eddb5a1114202ba385f66f131b1601feec11.json
+++ b/.sqlx/query-4623f989492e9eae6788ee9472f1138395b50cdfc9a28e9791e5484890f0201b.json
@@ -1,6 +1,6 @@
 {
   "db_name": "SQLite",
-  "query": "\n                select\n                    message.channel as \"channel: channel::Id\",\n                    message.sender as \"sender: login::Id\",\n                    id as \"id: Id\",\n                    message.body as \"body: Body\",\n                    message.sent_at as \"sent_at: DateTime\",\n                    message.sent_sequence as \"sent_sequence: Sequence\",\n                    deleted.deleted_at as \"deleted_at: DateTime\",\n                    deleted.deleted_sequence as \"deleted_sequence: Sequence\"\n                from message\n                left join message_deleted as deleted\n                    using (id)\n                where message.channel = $1\n                    and deleted.id is null\n            ",
+  "query": "\n                select\n                    message.channel as \"channel: channel::Id\",\n                    message.sender as \"sender: login::Id\",\n                    id as \"id: Id\",\n                    message.body as \"body: Body\",\n                    message.sent_at as \"sent_at: DateTime\",\n                    message.sent_sequence as \"sent_sequence: Sequence\",\n                    deleted.deleted_at as \"deleted_at?: DateTime\",\n                    deleted.deleted_sequence as \"deleted_sequence?: Sequence\"\n                from message\n                left join message_deleted as deleted\n                    using (id)\n                where message.channel = $1\n                    and deleted.id is null\n            ",
   "describe": {
     "columns": [
       {
@@ -34,12 +34,12 @@
         "type_info": "Integer"
       },
       {
-        "name": "deleted_at: DateTime",
+        "name": "deleted_at?: DateTime",
         "ordinal": 6,
         "type_info": "Text"
       },
       {
-        "name": "deleted_sequence: Sequence",
+        "name": "deleted_sequence?: Sequence",
         "ordinal": 7,
         "type_info": "Integer"
       }
@@ -54,9 +54,9 @@
       true,
       false,
       false,
-      true,
-      true
+      false,
+      false
     ]
   },
-  "hash": "40e0310af2814435cca882701b86eddb5a1114202ba385f66f131b1601feec11"
+  "hash": "4623f989492e9eae6788ee9472f1138395b50cdfc9a28e9791e5484890f0201b"
 }
diff --git a/.sqlx/query-8eebba45e8267b9eebc7b1ae7e18ecb51d54d1e304dcbd847de145c0c75423a7.json b/.sqlx/query-8eebba45e8267b9eebc7b1ae7e18ecb51d54d1e304dcbd847de145c0c75423a7.json
deleted file mode 100644
index 0394bc5..0000000
--- a/.sqlx/query-8eebba45e8267b9eebc7b1ae7e18ecb51d54d1e304dcbd847de145c0c75423a7.json
+++ /dev/null
@@ -1,20 +0,0 @@
-{
-  "db_name": "SQLite",
-  "query": "\n                update message\n                set body = \"\"\n                where id = $1\n                returning 1 as \"blanked: bool\"\n            ",
-  "describe": {
-    "columns": [
-      {
-        "name": "blanked: bool",
-        "ordinal": 0,
-        "type_info": "Null"
-      }
-    ],
-    "parameters": {
-      "Right": 1
-    },
-    "nullable": [
-      null
-    ]
-  },
-  "hash": "8eebba45e8267b9eebc7b1ae7e18ecb51d54d1e304dcbd847de145c0c75423a7"
-}
diff --git a/.sqlx/query-947df87da285e68a710443f05ffc52cb1712545ff539df49bbd47df194012f79.json b/.sqlx/query-947df87da285e68a710443f05ffc52cb1712545ff539df49bbd47df194012f79.json
deleted file mode 100644
index d4bb122..0000000
--- a/.sqlx/query-947df87da285e68a710443f05ffc52cb1712545ff539df49bbd47df194012f79.json
+++ /dev/null
@@ -1,56 +0,0 @@
-{
-  "db_name": "SQLite",
-  "query": "\n                select\n                    id as \"id: Id\",\n                    name.display_name as \"display_name: String\",\n                    name.canonical_name as \"canonical_name: String\",\n                    channel.created_at as \"created_at: DateTime\",\n                    channel.created_sequence as \"created_sequence: Sequence\",\n                    deleted.deleted_at as \"deleted_at?: DateTime\",\n                    deleted.deleted_sequence as \"deleted_sequence?: Sequence\"\n                from channel\n                left join channel_name as name\n                    using (id)\n                left join channel_deleted as deleted\n                    using (id)\n                where coalesce(channel.created_sequence <= $1, true)\n                order by name.canonical_name\n            ",
-  "describe": {
-    "columns": [
-      {
-        "name": "id: Id",
-        "ordinal": 0,
-        "type_info": "Text"
-      },
-      {
-        "name": "display_name: String",
-        "ordinal": 1,
-        "type_info": "Text"
-      },
-      {
-        "name": "canonical_name: String",
-        "ordinal": 2,
-        "type_info": "Text"
-      },
-      {
-        "name": "created_at: DateTime",
-        "ordinal": 3,
-        "type_info": "Text"
-      },
-      {
-        "name": "created_sequence: Sequence",
-        "ordinal": 4,
-        "type_info": "Integer"
-      },
-      {
-        "name": "deleted_at?: DateTime",
-        "ordinal": 5,
-        "type_info": "Text"
-      },
-      {
-        "name": "deleted_sequence?: Sequence",
-        "ordinal": 6,
-        "type_info": "Integer"
-      }
-    ],
-    "parameters": {
-      "Right": 1
-    },
-    "nullable": [
-      false,
-      true,
-      true,
-      false,
-      false,
-      true,
-      true
-    ]
-  },
-  "hash": "947df87da285e68a710443f05ffc52cb1712545ff539df49bbd47df194012f79"
-}
diff --git a/.sqlx/query-2f4def5e6aa14d9bc4ca5db0d1f81953cd5f584b76ca59ece17d9ef2ce29ee9c.json b/.sqlx/query-9f611a3351f22ed16d67d41602b8befafe751e9caeb0d5f279731e04c6925f46.json
index c1da170..2d1f49e 100644
--- a/.sqlx/query-2f4def5e6aa14d9bc4ca5db0d1f81953cd5f584b76ca59ece17d9ef2ce29ee9c.json
+++ b/.sqlx/query-9f611a3351f22ed16d67d41602b8befafe751e9caeb0d5f279731e04c6925f46.json
@@ -1,6 +1,6 @@
 {
   "db_name": "SQLite",
-  "query": "\n                select\n                    id as \"id: Id\",\n                    display_name as \"display_name: String\",\n                    canonical_name as \"canonical_name: String\",\n                    created_sequence as \"created_sequence: Sequence\",\n                    created_at as \"created_at: DateTime\"\n                from login\n                    where coalesce(created_sequence <= $1, true)\n                    order by created_sequence\n            ",
+  "query": "\n                select\n                    id as \"id: Id\",\n                    display_name as \"display_name: String\",\n                    canonical_name as \"canonical_name: String\",\n                    created_sequence as \"created_sequence: Sequence\",\n                    created_at as \"created_at: DateTime\"\n                from login\n                    where coalesce(created_sequence <= $1, true)\n                    order by canonical_name\n            ",
   "describe": {
     "columns": [
       {
@@ -40,5 +40,5 @@
       false
     ]
   },
-  "hash": "2f4def5e6aa14d9bc4ca5db0d1f81953cd5f584b76ca59ece17d9ef2ce29ee9c"
+  "hash": "9f611a3351f22ed16d67d41602b8befafe751e9caeb0d5f279731e04c6925f46"
 }
diff --git a/.sqlx/query-a4b34593fdf71bb911beb850cfa88adb346b1770e32785166bd43cb853143a7f.json b/.sqlx/query-a4b34593fdf71bb911beb850cfa88adb346b1770e32785166bd43cb853143a7f.json
new file mode 100644
index 0000000..e886759
--- /dev/null
+++ b/.sqlx/query-a4b34593fdf71bb911beb850cfa88adb346b1770e32785166bd43cb853143a7f.json
@@ -0,0 +1,56 @@
+{
+  "db_name": "SQLite",
+  "query": "\n                select\n                    channel.id as \"id: Id\",\n                    name.display_name as \"display_name?: String\",\n                    name.canonical_name as \"canonical_name?: String\",\n                    channel.created_at as \"created_at: DateTime\",\n                    channel.created_sequence as \"created_sequence: Sequence\",\n                    deleted.deleted_at as \"deleted_at?: DateTime\",\n                    deleted.deleted_sequence as \"deleted_sequence?: Sequence\"\n                from channel\n                left join channel_name as name\n                    using (id)\n                left join channel_deleted as deleted\n                    using (id)\n                left join message\n                    on channel.id = message.channel\n                where channel.created_at < $1\n                    and message.id is null\n                    and deleted.id is null\n            ",
+  "describe": {
+    "columns": [
+      {
+        "name": "id: Id",
+        "ordinal": 0,
+        "type_info": "Text"
+      },
+      {
+        "name": "display_name?: String",
+        "ordinal": 1,
+        "type_info": "Null"
+      },
+      {
+        "name": "canonical_name?: String",
+        "ordinal": 2,
+        "type_info": "Null"
+      },
+      {
+        "name": "created_at: DateTime",
+        "ordinal": 3,
+        "type_info": "Text"
+      },
+      {
+        "name": "created_sequence: Sequence",
+        "ordinal": 4,
+        "type_info": "Integer"
+      },
+      {
+        "name": "deleted_at?: DateTime",
+        "ordinal": 5,
+        "type_info": "Text"
+      },
+      {
+        "name": "deleted_sequence?: Sequence",
+        "ordinal": 6,
+        "type_info": "Integer"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false
+    ]
+  },
+  "hash": "a4b34593fdf71bb911beb850cfa88adb346b1770e32785166bd43cb853143a7f"
+}
diff --git a/.sqlx/query-ad1485f0a5514bcfaf68477723ae0f13e93a1f18213e208d3a181936a36da5fb.json b/.sqlx/query-ad1485f0a5514bcfaf68477723ae0f13e93a1f18213e208d3a181936a36da5fb.json
new file mode 100644
index 0000000..ce757ba
--- /dev/null
+++ b/.sqlx/query-ad1485f0a5514bcfaf68477723ae0f13e93a1f18213e208d3a181936a36da5fb.json
@@ -0,0 +1,56 @@
+{
+  "db_name": "SQLite",
+  "query": "\n                select\n                    id as \"id: Id\",\n                    name.display_name as \"display_name?: String\",\n                    name.canonical_name as \"canonical_name?: String\",\n                    channel.created_at as \"created_at: DateTime\",\n                    channel.created_sequence as \"created_sequence: Sequence\",\n                    deleted.deleted_at as \"deleted_at?: DateTime\",\n                    deleted.deleted_sequence as \"deleted_sequence?: Sequence\"\n                from channel\n                left join channel_name as name\n                    using (id)\n                left join channel_deleted as deleted\n                    using (id)\n                where channel.created_sequence <= $1\n                order by name.canonical_name\n            ",
+  "describe": {
+    "columns": [
+      {
+        "name": "id: Id",
+        "ordinal": 0,
+        "type_info": "Text"
+      },
+      {
+        "name": "display_name?: String",
+        "ordinal": 1,
+        "type_info": "Null"
+      },
+      {
+        "name": "canonical_name?: String",
+        "ordinal": 2,
+        "type_info": "Null"
+      },
+      {
+        "name": "created_at: DateTime",
+        "ordinal": 3,
+        "type_info": "Text"
+      },
+      {
+        "name": "created_sequence: Sequence",
+        "ordinal": 4,
+        "type_info": "Integer"
+      },
+      {
+        "name": "deleted_at?: DateTime",
+        "ordinal": 5,
+        "type_info": "Text"
+      },
+      {
+        "name": "deleted_sequence?: Sequence",
+        "ordinal": 6,
+        "type_info": "Integer"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false
+    ]
+  },
+  "hash": "ad1485f0a5514bcfaf68477723ae0f13e93a1f18213e208d3a181936a36da5fb"
+}
diff --git a/.sqlx/query-e718f4064cbb3d1b27049450121451dbcf01e8bec8a987b58c699b27b5d737af.json b/.sqlx/query-e718f4064cbb3d1b27049450121451dbcf01e8bec8a987b58c699b27b5d737af.json
new file mode 100644
index 0000000..0c21ec1
--- /dev/null
+++ b/.sqlx/query-e718f4064cbb3d1b27049450121451dbcf01e8bec8a987b58c699b27b5d737af.json
@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "\n                update message\n                set body = ''\n                where id = $1\n            ",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": []
+  },
+  "hash": "e718f4064cbb3d1b27049450121451dbcf01e8bec8a987b58c699b27b5d737af"
+}