aokolnychyi commented on code in PR #8755:
URL: https://github.com/apache/iceberg/pull/8755#discussion_r1445973562
##########
api/src/main/java/org/apache/iceberg/types/TypeUtil.java:
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@@ -452,6 +454,68 @@ private static void checkSchemaCompatibility(
}
}
+ /**
+ * Estimates the number of bytes a value for a given field may occupy in
memory.
+ *
+ * <p>This method approximates the memory size based on the internal Java
representation defined
+ * by {@link Type.TypeID}. It is important to note that the actual size
might differ from this
+ * estimation. The method is designed to handle a variety of data types,
including primitive
+ * types, strings, and nested types such as structs, maps, and lists.
+ *
+ * @param field a field for which to estimate the size
+ * @return the estimated size in bytes of the field's value in memory
+ */
+ public static long defaultSize(Types.NestedField field) {
+ return defaultSize(field.type());
+ }
+
+ private static long defaultSize(Type type) {
+ switch (type.typeId()) {
+ case BOOLEAN:
+ // the size of a boolean variable is virtual machine dependent
+ // it is common to believe booleans occupy 1 byte in most JVMs
+ return 1;
+ case INTEGER:
+ case FLOAT:
+ case DATE:
+ // ints and floats occupy 4 bytes
+ // dates are internally represented as ints
+ return 4;
+ case LONG:
+ case DOUBLE:
+ case TIME:
+ case TIMESTAMP:
+ // longs and doubles occupy 8 bytes
+ // times and timestamps are internally represented as longs
+ return 8;
+ case STRING:
+ // 12 (header) + 12 (fields) + 16 (array overhead) + 20 (10 chars, 2
bytes each) = 60 bytes
+ return 60;
Review Comment:
Synced a bit offline on this one. I think it should be fine to start with
the current solution and then see actual use cases when it will become a
problem. There are multiple ways to approach it but all of them are
substantially more complicated.
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