Use thread local for groupby raw key holders #5419
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...n/java/org/apache/pinot/core/query/aggregation/groupby/DictionaryBasedGroupKeyGenerator.java
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mayankshriv
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May 20, 2020
| if (longOverflow) { | ||
| _globalGroupIdUpperBound = numGroupsLimit; | ||
| _rawKeyHolder = new ArrayMapBasedHolder(_globalGroupIdUpperBound); | ||
| if (!mapBasedRawKeyHolders.containsKey(ArrayMapBasedHolder.class.getName())) { | ||
| mapBasedRawKeyHolders.put(ArrayMapBasedHolder.class.getName(), new ArrayMapBasedHolder(_globalGroupIdUpperBound).getInternal()); |
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I think initializing to _globalGroupIdUpperBound got introduced in #5291. For many cases with multiple group by columns (high cardinality and/or MV columns) this number can be huge. Unclear to me if making this thread-local will protect against such cases that may require allocating huge chunk of memory upfornt.
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True. I feel we may need to have a range of groupIdBound, and only do thread local for them. if it's too small or too large, maybe just create new objects without and with initial size.
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snleee
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