news: Firehose block ingestor downgrade caution

Author: Filippo Costa

NEWS.md

@@ -13,6 +13,7 @@ New `graph-node` installations now **mandate** PostgreSQL to use C locale and UT
 - **AND/OR filters.** AND/OR logical operators in `where` filters have been one of `graph-node`'s [most awaited](https://github.com/graphprotocol/graph-node/issues?q=is%3Aissue+sort%3Areactions-%2B1-desc) features. They do exactly what you would expect them to do, and are very powerful. [#579](https://github.com/graphprotocol/graph-node/issues/579), [#4080](https://github.com/graphprotocol/graph-node/pull/4080), [#4171](https://github.com/graphprotocol/graph-node/pull/4171)
 - **IPFS file data sources.** IPFS file data sources allow subgraph developers to query offchain information from IPFS directly in mappings. This feature is the culmination of much community and development efforts (GIP [here](https://forum.thegraph.com/t/gip-file-data-sources/2721)). A future iteration of this feature will also include a so-called "Availability Chain", allowing IPFS file data sources to contribute to Proofs of Indexing. At the moment, entity updates that originate from these data sources' handlers do **not** contribute to PoIs. [#4147](https://github.com/graphprotocol/graph-node/pull/4147), [#4162](https://github.com/graphprotocol/graph-node/pull/4162), and many others!
 - **Sorting by child entities** (a.k.a. nested sorting). You can now `orderBy` properties of child entities. [#4058](https://github.com/graphprotocol/graph-node/pull/4058), [#3737](https://github.com/graphprotocol/graph-node/issues/3737), [#3096](https://github.com/graphprotocol/graph-node/pull/3096)
+- Added support for a Firehose-based block ingestor. **Indexers that use the new Firehose-based block ingestor **cannot** automatically switch back to RPC.** In order to downgrade, indexers must manually delete all blocks accumulated by Firehose in the database. For this reason, we suggest caution when switching over from RPC to Firehose. [#4059](https://github.com/graphprotocol/graph-node/issues/4059), [#4204](https://github.com/graphprotocol/graph-node/pull/4204), [#4216](https://github.com/graphprotocol/graph-node/pull/4216)
 - Fields of type `Bytes` can now use less than and greater than filters. [#4285](https://github.com/graphprotocol/graph-node/pull/4285)
 - "userinfo" is now allowed in IPFS URLs (e.g. `https://foo:[email protected]:5001/`). [#4252](https://github.com/graphprotocol/graph-node/pull/4252)
 - The default for `GRAPH_IPFS_TIMEOUT` is now 60 seconds instead of 30. [#4324](https://github.com/graphprotocol/graph-node/pull/4324)
@@ -25,7 +26,6 @@ graph_elasticsearch_logs_sent
 - Turned "Flushing logs to Elasticsearch" log into a Prometheus metric (`graph_elasticsearch_logs_sent`) to reduce log noise. [#4333](https://github.com/graphprotocol/graph-node/pull/4333)
 - New materialized view `info.chain_sizes`, which works the same way as the already existing `info.subgraph_sizes` and `info.table_sizes`. [#4318](https://github.com/graphprotocol/graph-node/pull/4318)
 - New `graphman stats` subcommands `set-target` and `target` to manage statistics targets for specific deployments (i.e. how much data PostgreSQL samples when analyzing a table). [#4092](https://github.com/graphprotocol/graph-node/pull/4092)
-- Added support for a Firehose-based block ingestor. [#4059](https://github.com/graphprotocol/graph-node/issues/4059), [#4204](https://github.com/graphprotocol/graph-node/pull/4204), [#4216](https://github.com/graphprotocol/graph-node/pull/4216)
 
 ### Fixes