Instead of trying to write some function and slow down the SELECT query, I thought of another way of doing this...
Create an extra field in your database that holds the result from the following Class and when you insert a new row, run the field value that will be naturally sorted through this class and save its result in the extra field. Then instead of sorting by your original field, sort by the extra field.
String nsFieldVal = new NaturalSortString(getFieldValue(), 4).toString()
The above means:
- Create a NaturalSortString for the String returned from getFieldValue()
- Allow up to 4 bytes to store each character or number (4 bytes = ffff = 65535)
| field(32) | nsfield(161) |
a1 300610001
String sortString = new NaturalSortString(getString(), 4).toString()
import StringUtils;
/**
* Creates a string that allows natural sorting in a SQL database
* eg, 0 1 1a 2 3 3a 10 100 a a1 a1a1 b
*/
public class NaturalSortString {
private String inStr;
private int byteSize;
private StringBuilder out = new StringBuilder();
/**
* A byte stores the hex value (0 to f) of a letter or number.
* Since a letter is two bytes, the minimum byteSize is 2.
*
* 2 bytes = 00 - ff (max number is 255)
* 3 bytes = 000 - fff (max number is 4095)
* 4 bytes = 0000 - ffff (max number is 65535)
*
* For example:
* dog123 = 64,6F,67,7B and thus byteSize >= 2.
* dog280 = 64,6F,67,118 and thus byteSize >= 3.
*
* For example:
* The String, "There are 1000000 spots on a dalmatian" would require a byteSize that can
* store the number '1000000' which in hex is 'f4240' and thus the byteSize must be at least 5
*
* The dbColumn size to store the NaturalSortString is calculated as:
* > originalStringColumnSize x byteSize + 1
* The extra '1' is a marker for String type - Letter, Number, Symbol
* Thus, if the originalStringColumn is varchar(32) and the byteSize is 5:
* > NaturalSortStringColumnSize = 32 x 5 + 1 = varchar(161)
*
* The byteSize must be the same for all NaturalSortStrings created in the same table.
* If you need to change the byteSize (for instance, to accommodate larger numbers), you will
* need to recalculate the NaturalSortString for each existing row using the new byteSize.
*
* @param str String to create a natural sort string from
* @param byteSize Per character storage byte size (minimum 2)
* @throws Exception See the error description thrown
*/
public NaturalSortString(String str, int byteSize) throws Exception {
if (str == null || str.isEmpty()) return;
this.inStr = str;
this.byteSize = Math.max(2, byteSize); // minimum of 2 bytes to hold a character
setStringType();
iterateString();
}
private void setStringType() {
char firstchar = inStr.toLowerCase().subSequence(0, 1).charAt(0);
if (Character.isLetter(firstchar)) // letters third
out.append(3);
else if (Character.isDigit(firstchar)) // numbers second
out.append(2);
else // non-alphanumeric first
out.append(1);
}
private void iterateString() throws Exception {
StringBuilder n = new StringBuilder();
for (char c : inStr.toLowerCase().toCharArray()) { // lowercase for CASE INSENSITIVE sorting
if (Character.isDigit(c)) {
// group numbers
n.append(c);
continue;
}
if (n.length() > 0) {
addInteger(n.toString());
n = new StringBuilder();
}
addCharacter(c);
}
if (n.length() > 0) {
addInteger(n.toString());
}
}
private void addInteger(String s) throws Exception {
int i = Integer.parseInt(s);
if (i >= (Math.pow(16, byteSize)))
throw new Exception("naturalsort_bytesize_exceeded");
out.append(StringUtils.padLeft(Integer.toHexString(i), byteSize));
}
private void addCharacter(char c) {
//TODO: Add rest of accented characters
if (c >= 224 && c <= 229) // set accented a to a
c = 'a';
else if (c >= 232 && c <= 235) // set accented e to e
c = 'e';
else if (c >= 236 && c <= 239) // set accented i to i
c = 'i';
else if (c >= 242 && c <= 246) // set accented o to o
c = 'o';
else if (c >= 249 && c <= 252) // set accented u to u
c = 'u';
else if (c >= 253 && c <= 255) // set accented y to y
c = 'y';
out.append(StringUtils.padLeft(Integer.toHexString(c), byteSize));
}
@Override
public String toString() {
return out.toString();
}
}
For completeness, below is the StringUtils.padLeft method:
public static String padLeft(String s, int n) {
if (n - s.length() == 0) return s;
return String.format("%0" + (n - s.length()) + "d%s", 0, s);
}
The result should come out like the following
-1
-a
0
1
1.0
1.01
1.1.1
1a
1b
9
10
10a
10ab
11
12
12abcd
100
a
a1a1
a1a2
a-1
a-2
áviacion
b
c1
c2
c12
c100
d
d1.1.1
e
