wgtmac commented on code in PR #240:
URL: https://github.com/apache/parquet-format/pull/240#discussion_r1606208597
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src/main/thrift/parquet.thrift:
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@@ -982,6 +1054,23 @@ union ColumnOrder {
* `-0.0` should be written into the min statistics field.
*/
1: TypeDefinedOrder TYPE_ORDER;
+
+ /**
+ * The order only applies to GEOMETRY logical type.
+ *
+ * Please note that geometry objects cannot be compared directly. This order
aims to
+ * provide an approach to build a bounding box for geometry objects in the
same page
+ * or column chunk.
+ *
+ * In this order, all 2D geometries are regarded as a collection of
coordinate (x, y).
+ * For example, POINT has one coordinate, LINESTRING has two coordinates,
and POLYGON
+ * might have three or more coordinates. A bounding box is the combination
of x_min,
+ * x_max, y_min, and y_max of all coordinates from all geometry values. For
simplexty,
+ * min_value field in the Statistics/ColumnIndex is encoded as the
concatenation of
+ * PLAIN-encoded DOUBLE-typed x_min and y_min values. Similarly, max_value
field is
+ * encoded as the concatenation of PLAIN-encoded DOUBLE-typed x_max and
y_max values.
Review Comment:
Here the column statistics are the aggregate index for a group of geometry
values. For example, usually the column statistics are collected from a data
page of 10,000 values where bbox is more suitable. CMIW, S2/H3 covering might
be more efficient in spatial join or record-level filtering.
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