normanj-bitquill commented on code in PR #3927:
URL: https://github.com/apache/calcite/pull/3927#discussion_r1729550440
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core/src/main/java/org/apache/calcite/runtime/SqlFunctions.java:
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@@ -2834,6 +2834,28 @@ public static ByteString bitAnd(ByteString b0,
ByteString b1) {
return binaryOperator(b0, b1, (x, y) -> (byte) (x & y));
}
+ /** Helper function for implementing <code>BITCOUNT</code>. Counts the number
+ * of bits set in an integer value. */
+ public static long bitCount(long b) {
+ return Long.bitCount(b);
+ }
+
+ /** Helper function for implementing <code>BITCOUNT</code>. Counts the number
+ * of bits set in the integer portion of a decimal value. */
+ public static long bitCount(BigDecimal b) {
+ return Long.bitCount(b.longValue());
Review Comment:
I did some more testing with MySQL.
* bitcount(18446744073709551615) = 64
* bitcount(18446744073709551616 or greater) = 63
* bitcount(-9223372036854775808 or less) = 1
I have updating the implementation of `bitcount(BigDecimal)` to match this
behaviour. This is only enabled in the MySQL library.
It should match MySQL behaviour at the moment, but since this is not really
documented
https://dev.mysql.com/doc/refman/8.4/en/bit-functions.html#function_bit-count
perhaps this is not worth keeping and could change at any time.
In general is it better to match MySQL behaviour (for a MySQL specific
function) or is it better to take the simpler approach?
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