docs: update events (#6658)

* docs: update events

* lint++

* lint++

docs/app-dev/indexing-transactions.md

@@ -31,24 +31,61 @@ For example:
 
 would be equal to the composite key of `jack.account.number`.
 
-Let's take a look at the `[tx_index]` config section:
+By default, Tendermint will index all transactions by their respective hashes
+and height and blocks by their height.
+
+## Configuration
+
+Operators can configure indexing via the `[tx_index]` section. The `indexer`
+field takes a series of supported indexers. If `null` is included, indexing will
+be turned off regardless of other values provided.
 
 ```toml
-##### transactions indexer configuration options #####
-[tx_index]
+[tx-index]
 
-# What indexer to use for transactions
+# The backend database list to back the indexer.
+# If list contains null, meaning no indexer service will be used.
+#
+# The application will set which txs to index. In some cases a node operator will be able
+# to decide which txs to index based on configuration set in the application.
 #
 # Options:
 #   1) "null"
 #   2) "kv" (default) - the simplest possible indexer, backed by key-value storage (defaults to levelDB; see DBBackend).
-indexer = "kv"
+#     - When "kv" is chosen "tx.height" and "tx.hash" will always be indexed.
+#   3) "psql" - the indexer services backed by PostgreSQL.
+# indexer = []
 ```
 
-By default, Tendermint will index all transactions by their respective hashes
-and height and blocks by their height.
+### Supported Indexers
+
+#### KV
 
-You can turn off indexing completely by setting `tx_index` to `null`.
+The `kv` indexer type is an embedded key-value store supported by the main
+underling Tendermint database. Using the `kv` indexer type allows you to query
+for block and transaction events directly against Tendermint's RPC. However, the
+query syntax is limited and so this indexer type might be deprecated or removed
+entirely in the future.
+
+#### PostgreSQL
+
+The `psql` indexer type allows an operator to enable block and transaction event
+indexing by proxying it to an external PostgreSQL instance allowing for the events
+to be stored in relational models. Since the events are stored in a RDBMS, operators
+can leverage SQL to perform a series of rich and complex queries that are not
+supported by the `kv` indexer type. Since operators can leverage SQL directly,
+searching is not enabled for the `psql` indexer type via Tendermint's RPC -- any
+such query will fail.
+
+Note, the SQL schema is stored in `state/indexer/sink/psql/schema.sql` and operators
+must explicitly create the relations prior to starting Tendermint and enabling
+the `psql` indexer type.
+
+Example:
+
+```shell
+$ psql ... -f state/indexer/sink/psql/schema.sql
+```
 
 ## Default Indexes
 

node/setup.go

@@ -81,13 +81,14 @@ func createAndStartIndexerService(
 
 	eventSinks := []indexer.EventSink{}
 
-	// Check duplicated sinks.
+	// check for duplicated sinks
 	sinks := map[string]bool{}
 	for _, s := range config.TxIndex.Indexer {
 		sl := strings.ToLower(s)
 		if sinks[sl] {
 			return nil, nil, errors.New("found duplicated sinks, please check the tx-index section in the config.toml")
 		}
+
 		sinks[sl] = true
 	}
 
@@ -95,25 +96,31 @@ loop:
 	for k := range sinks {
 		switch k {
 		case string(indexer.NULL):
-			// when we see null in the config, the eventsinks will be reset with the nullEventSink.
+			// When we see null in the config, the eventsinks will be reset with the
+			// nullEventSink.
 			eventSinks = []indexer.EventSink{null.NewEventSink()}
 			break loop
+
 		case string(indexer.KV):
 			store, err := dbProvider(&cfg.DBContext{ID: "tx_index", Config: config})
 			if err != nil {
 				return nil, nil, err
 			}
+
 			eventSinks = append(eventSinks, kv.NewEventSink(store))
+
 		case string(indexer.PSQL):
 			conn := config.TxIndex.PsqlConn
 			if conn == "" {
 				return nil, nil, errors.New("the psql connection settings cannot be empty")
 			}
+
 			es, _, err := psql.NewEventSink(conn, chainID)
 			if err != nil {
 				return nil, nil, err
 			}
 			eventSinks = append(eventSinks, es)
+
 		default:
 			return nil, nil, errors.New("unsupported event sink type")
 		}

state/indexer/sink/psql/schema.sql

@@ -25,9 +25,7 @@ CREATE TABLE tx_events (
     created_at TIMESTAMPTZ NOT NULL,
     chain_id VARCHAR NOT NULL,
     UNIQUE (hash, key),
-    FOREIGN KEY (tx_result_id)
-        REFERENCES tx_results(id)
-        ON DELETE CASCADE
+    FOREIGN KEY (tx_result_id) REFERENCES tx_results(id) ON DELETE CASCADE
 );
 CREATE INDEX idx_block_events_key_value ON block_events(key, value);
 CREATE INDEX idx_tx_events_key_value ON tx_events(key, value);