Add indexes to docs

apps/web/pages/docs/_meta.json

@@ -3,6 +3,7 @@
   "installation": "Installation",
   "quickstart": "Quickstart",
   "api": "API",
+  "indexes": "Indexes",
   "migrations": "Migrations",
   "patterns": "Patterns",
   "evolu-server": "Evolu Server",

apps/web/pages/docs/indexes.mdx

@@ -0,0 +1,48 @@
+import { Callout } from "nextra-theme-docs";
+
+# Indexes
+
+Are your queries taking too long to run? Measure them with
+the `logExecutionTime` option.
+
+```ts
+const allTodos = evolu.createQuery(
+  (db) => db.selectFrom("todo").orderBy("createdAt").selectAll(),
+  {
+    logExecutionTime: true,
+    // logExplainQueryPlan: false,
+  },
+);
+```
+
+<Callout type="info" emoji="ℹ️">
+  While indexes are not necessary for development, they are almost always
+  required for production. But before adding them, measure and analyze the query
+  first with `logExecutionTime` and `logExplainQueryPlan` createQuery options.
+</Callout>
+
+If you want to learn what indexes are and how they should be used, check this
+article [squeezing-performance-from-sqlite-indexes](https://medium.com/@JasonWyatt/squeezing-performance-from-sqlite-indexes-indexes-c4e175f3c346).
+
+## Usage
+
+```ts
+const indexes = [
+  createIndex("indexTodoCreatedAt").on("todo").column("createdAt"),
+];
+
+const evolu = createEvolu(Database, { indexes });
+```
+
+That's all we have to do. Evolu automatically adds new indexes and drops
+old ones (not listed in the indexes array).
+
+## Index Recommendations (SQLite Expert)
+
+SQLite has an excellent [CLI tool](https://sqlite.org/cli.html#index_recommendations_sqlite_expert_)
+for index recommendations. Download "Precompiled Binaries" [here](https://www.sqlite.org/download.html), open a file or create a DB, run `.expert`, and paste the query SQL there.
+
+To get the query SQL (for copy-pasting to .expert), use the `logExecutionTime`
+createQuery options.
+To get SQL for creating tables, use the global `logSql` Evolu config option
+and reset Evolu.