wgtmac commented on code in PR #250:
URL: https://github.com/apache/parquet-format/pull/250#discussion_r1621008508
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src/main/thrift/parquet.thrift:
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@@ -1115,6 +1189,34 @@ union EncryptionAlgorithm {
2: AesGcmCtrV1 AES_GCM_CTR_V1
}
+/**
+ * Embedded metadata page.
+ *
+ * A metadata page is a data page used to store metadata about
+ * the data stored in the file. This is a key feature of PAR3
+ * footers which allow for deferred decoding of metadata.
+ *
+ * For common use cases the current recommendation is to use a
+ * an encoding that supported random access but implementations may choose
+ * other configuration parameters if necessary. Implementations
+ * SHOULD consider allowing configurability per page to allow for end-users
+ * to optimize size vs compute trade-offs that make sense for their use-case.
+ *
+ * Statistics for Metadata pages SHOULD NOT be written.
+ *
+ * Structs of this type should never be written in PAR1.
+ */
+struct MetadataPage {
+ // A serialized page including metadata thrift header and data.
+ 1: required binary page
+ // Optional compression applied to the page.
+ 2: optional CompressionCodec compression
+ // Number of elements stored. This is duplicated here to help in
+ // use-cases where knowing the total number of elements up front for
+ // computation would be useful.
+ 3: num_values
Review Comment:
Is it possible to add a `list<i32>` with `num_values + 1` size to indicate
the offsets to each element before compression to support random access? Or is
it supposed to use fixed-length element at all times?
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