chore: import upstream snapshot with attribution

docs/develop/switch_doc_engine.md

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+---
+sidebar_position: 3
+slug: /switch_doc_engine
+sidebar_custom_props: {
+  categoryIcon: LucideShuffle
+}
+---
+# Switch document engine
+
+Switch your doc engine from Elasticsearch to Infinity.
+
+---
+
+RAGFlow uses Elasticsearch by default for storing full text and vectors. To switch to [Infinity](https://github.com/infiniflow/infinity/), follow these steps:
+
+:::caution WARNING
+Switching to Infinity on a Linux/arm64 machine is not yet officially supported.
+:::
+
+1. Stop all running containers:
+
+   ```bash
+   $ docker compose -f docker/docker-compose.yml down -v
+   ```
+
+:::caution WARNING
+`-v` will delete the docker container volumes, and the existing data will be cleared.
+:::
+
+2. Set `DOC_ENGINE` in **docker/.env** to `infinity`.
+
+3. Start the containers:
+
+   ```bash
+   $ docker compose -f docker-compose.yml up -d
+   ```