core: reduce tag index memory overhead#1878
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brharrington merged 1 commit intoNetflix:mainfrom Feb 27, 2026
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Reduce initial capacity for temporary HashSets used during index construction. Based on production data, the number of unique keys is typically under 10k and unique values are roughly 1/6th of the number of items, so items.length was significantly oversized for both. Flatten itemTags from Array[Array[Int]] to a pair of flat arrays (offsets + data). This eliminates one Array[Int] object per item, saving ~24 bytes of JVM object overhead each. For a production index with ~16M items, this saves roughly 390MB.
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Reduce initial capacity for temporary HashSets used during index construction. Based on production data, the number of unique keys is typically under 10k and unique values are roughly 1/6th of the number of items, so items.length was significantly oversized for both.
Flatten itemTags from Array[Array[Int]] to a pair of flat arrays (offsets + data). This eliminates one Array[Int] object per item, saving ~24 bytes of JVM object overhead each. For a production index with ~16M items, this saves roughly 390MB.