and even better use "string sortable long" (code taken from SOLR)
(for reverse order don't forget to subtrcact value from Long.MAX as in
message before)
// uses binary representation of an int to build a string of
// chars that will sort correctly. Only char ranges
// less than 0xd800 will be used to avoid UCS-16 surrogates.
// we can use the lowest 15 bits of a char, (or a mask of 0x7fff)
public static int long2bytes(long val, byte[] out, int offset) {
val += Long.MIN_VALUE;
out[offset++] = (byte) 0;
out[offset++] = (byte) (val >>> 60);
out[offset++] = (byte) (val >>> 53 & 0x7f);
out[offset++] = (byte) (val >>> 45 & 0xff);
out[offset++] = (byte) (val >>> 38 & 0x7f);
out[offset++] = (byte) (val >>> 30 & 0xff);
out[offset++] = (byte) (val >>> 23 & 0x7f);
out[offset++] = (byte) (val >>> 15 & 0xff);
out[offset++] = (byte) (val >>> 8 & 0x7f);
out[offset] = (byte) (val & 0xff);
return SORTABLE_LONG_SIZEOF;
}
public static long bytes2long(byte[] in, int offset, int len) {
offset++; // skip 1 byte
long val = ((long) in[offset++] & 0xff) << 60;
val |= ((long) in[offset++] & 0x7f) << 53;
val |= ((long) in[offset++] & 0xff) << 45;
val |= ((long) in[offset++] & 0x7f) << 38;
val |= ((long) in[offset++] & 0xff) << 30;
val |= ((long) in[offset++] & 0x7f) << 23;
val |= ((long) in[offset++] & 0xff) << 15;
val |= ((long) in[offset++] & 0x7f) << 8;
val |= ((long) in[offset] & 0xff);
val -= Long.MIN_VALUE;
return val;
}
2010/6/25 Andrey Stepachev <[email protected]>:
> use Long.MAX - incrementColumnValue() as qualifier
>
> 2010/6/25 N Kapshoo <[email protected]>:
>> I have a 'long' number that I get by using
>> HTable.'incrementColumnValue'. This long is used as the qualifier id
>> on a columnFamily.
>>
>> However in my listings, I always want the latest number first
>> (descending order basically).
>>
>> Currently I call the NavigableMap.descendingKeySet after I do the 'Get'.
>>
>> Is this the optimal way of doing it? Can I do something that can be
>> faster? Especially if I start filtering out and getting only first
>> 1000 etc then this wont work.
>>
>> How should I go about this? Change the key or is there something else
>> I can do while creating the table, doing a Get etc?
>>
>> Thanks.
>>
>
