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Currently, top-level scalar columns in parquet files can be used at runtime to prune row-groups by evaluating certain conjuncts over the column's dictionary (if available). This change extends such pruning to scalar values that are stored in collection type columns. Currently, dictionary pruning works by finding eligible conjuncts for top-level slots. Since only top-level slots are supported, the slots are implicitly part of the scan node's tuple descriptor. With this change, we track eligible conjuncts by slot as well as the tuple that contains the slot (either top-level or nested collection). Since collection conjuncts are already managed by a map that associates tuple descriptors to a list of their conjuncts, this extension follows the existing representation. The frontend builds the mapping of SlotId to conjuncts that are dictionary filterable. This mapping now includes SlotId's that reference nested tuples. The backend is adjusted to use the same representation. In addition, collection readers are decomposed into scalar filterable columns and other, non-dictionary filterable readers. When filtering a row group using a conjunct associated to a (possibly) nested collection type, an additional tuple buffer is allocated per tuple descriptor. Testing: - e2e test extended to illustrate row-groups that are pruned by nested collection dictionary filters. Change-Id: If3a2abcfc3d0f7d18756816659fed77ce12668dd Reviewed-on: http://gerrit.cloudera.org:8080/8775 Reviewed-by: Tim Armstrong <tarmstrong@cloudera.com> Tested-by: Impala Public Jenkins