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.

1 files changed, 44 insertions, 0 deletions

diff --git a/.sqlx/query-9f611a3351f22ed16d67d41602b8befafe751e9caeb0d5f279731e04c6925f46.json b/.sqlx/query-9f611a3351f22ed16d67d41602b8befafe751e9caeb0d5f279731e04c6925f46.json
new file mode 100644
index 0000000..2d1f49e
--- /dev/null
+++ b/.sqlx/query-9f611a3351f22ed16d67d41602b8befafe751e9caeb0d5f279731e04c6925f46.json
@@ -0,0 +1,44 @@
+{
+  "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 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_sequence: Sequence",
+        "ordinal": 3,
+        "type_info": "Integer"
+      },
+      {
+        "name": "created_at: DateTime",
+        "ordinal": 4,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      false,
+      false,
+      false,
+      false,
+      false
+    ]
+  },
+  "hash": "9f611a3351f22ed16d67d41602b8befafe751e9caeb0d5f279731e04c6925f46"
+}