TessaIO commented on code in PR #17212:
URL: https://github.com/apache/druid/pull/17212#discussion_r1798907119
##########
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:
Let's suppose that we have 2 rows in Druid, ID 1, and ID 2, and in the JDBC
source we have only 1 row with ID 1. When we execute a query (Groupby for e.g)
with a lookup in the aggregation, it will probably fail (according to my
testing) with a null pointer exception because ID 2 doesn't exist in the JDBC
source (according to the old code of course).
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