add cache mode descriptions

Author: KSDaemon

packages/cubejs-backend-shared/src/shared-types.ts

@@ -1 +1,22 @@
+/*
+stale-if-slow (default) — equivalent to previously used renewQuery: false
+  If refresh keys are up-to-date, returns the value from cache
+  If refresh keys are expired, tries to return the value from the database
+    Returns fresh value from the database if the query executed in the database until the first “Continue wait” interval is reached
+    Returns stale value from cache otherwise
+
+stale-while-revalidate — AKA “backgroundRefresh”
+  If refresh keys are up-to-date, returns the value from cache
+  If refresh keys are expired, returns stale data from cache
+  Updates the cache in background
+
+must-revalidate — equivalent to previously used renewQuery: true
+  If refresh keys are up-to-date, returns the value from cache
+  If refresh keys are expired, tries to return the value from the database
+    Returns fresh value from the database even if it takes minutes and many “Continue wait” intervals
+
+no-cache — AKA “forceRefresh”
+  Skips refresh key checks
+  Returns fresh data from the database, even if it takes minutes and many “Continue wait” intervals
+*/
 export type CacheMode = 'stale-if-slow' | 'stale-while-revalidate' | 'must-revalidate' | 'no-cache';