Further update docs for incremental updates / change capture. (#269)

Author: badmonster0

docs/docs/core/flow_methods.mdx

@@ -93,8 +93,10 @@ CLI equivalence: `cocoindex update -L`
 A data source may enable one or multiple *change capture mechanisms*:
 
 *   Configured with a [refresh interval](flow_def#refresh-interval), which is generally applicable to all data sources.
+
 *   Specific data sources also provide their specific change capture mechanisms.
-    See documentations for specific data sources for details.
+    For example, [`GoogleDrive` source](../ops/sources#google-drive) allows polling recent modified files.
+    See documentations for specific data sources.
 
 Change capture mechanisms enables CocoIndex to continuously capture changes from the source data and update the target data accordingly, under live update mode.
 

docs/docs/ops/sources.md

@@ -71,7 +71,8 @@ The spec takes the following fields:
     If the file is deleted (or the current account no longer has access to), this change will not be detected by this change stream.
 
     So when a `GoogleDrive` source enabled `recent_changes_poll_interval`, it's still recommended to set a `refresh_interval`, with a larger value.
-    So that most changes can be covered by polling recent changes (with low latency), and remaining changes (files no longer exist or accessible) will still be covered (with a higher latency).
+    So that most changes can be covered by polling recent changes (with low latency, like 10 seconds), and remaining changes (files no longer exist or accessible) will still be covered (with a higher latency, like 5 minutes, and should be larger if you have a huge number of files like 1M).
+    In reality, configure them based on your requirement: how freshness do you need to target index to be?
 
     :::