TessaIO commented on code in PR #17212:
URL: https://github.com/apache/druid/pull/17212#discussion_r1796559858
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extensions-core/lookups-cached-single/src/main/java/org/apache/druid/server/lookup/LoadingLookup.java:
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@@ -74,14 +75,22 @@ public String apply(@Nullable final String key)
}
final String presentVal;
- try {
- presentVal = loadingCache.get(keyEquivalent, new
ApplyCallable(keyEquivalent));
+ presentVal = this.loadingCache.getIfPresent(keyEquivalent);
+ if (presentVal != null) {
return NullHandling.emptyToNullIfNeeded(presentVal);
}
- catch (ExecutionException e) {
- LOGGER.debug("value not found for key [%s]", key);
+
+ String val = this.dataFetcher.fetch(keyEquivalent);
+ if (val == null) {
return null;
}
+
+ Map<String, String> map = new HashMap<>();
+ map.put(keyEquivalent, val);
+
+ this.loadingCache.putAll(map);
+
+ return NullHandling.emptyToNullIfNeeded(val);
Review Comment:
The new change suggests that if we don't find the value in the cache we get
it from the dataFetcher (DB or URI) and then we update the cache, so in the
next probable query we have the value.
(The old code, if I get right, was just getting data from the loading cache
and if it just returns the value from there whether it exists or not, the cache
is never updated).
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