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, 0 insertions, 20 deletions

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"
-}