findepi commented on code in PR #6582:
URL: https://github.com/apache/iceberg/pull/6582#discussion_r1073253298
##########
core/src/main/java/org/apache/iceberg/puffin/StandardBlobTypes.java:
##########
@@ -26,4 +26,6 @@ private StandardBlobTypes() {}
* href="https://datasketches.apache.org/";>Apache DataSketches</a> library
*/
public static final String APACHE_DATASKETCHES_THETA_V1 =
"apache-datasketches-theta-v1";
+
+ public static final String NDV_BLOB = "ndv-blob";
Review Comment:
> I am wondering why Theta sketch is preferred over HLL. Is it because Theta
sketch works better for larger data, and has better set intersection and
difference operation?
Theta supports union, intersection and difference, HLL supports only union.
In my testing they were roughly similar in NDV quality for unions.
See results in
https://github.com/trinodb/trino/pull/14290#issuecomment-1262160870
> I have a side question for puffin file: Is puffin file only used to store
table level stats?
currently, yes
this is how Puffin is **currently** integrated in Iceberg spec.
there is ongoing work for having partition-level stats, see eg
https://github.com/apache/iceberg/pull/1985
https://github.com/apache/iceberg/issues/1832
https://github.com/apache/iceberg/issues/1833
> I am currently taking a look at the file level bloom filter and wondering
where I should save them
this comment from @rdblue looks relevant
https://github.com/apache/iceberg/issues/1832#issuecomment-757072379
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