/**
* Create an index file for the specified column.
*
* @param colname the column's name
* @return the time it took to run this method.
* @throws Exception
*/
public long createIndexFile() throws Exception {
long s = System.currentTimeMillis();
// fill idx file with hashsize empty records/lines (empty means filled with spaces)
int pkindex = def.getColPosition(def.getPK());
if (pkindex == -1) {
throw new Exception("Primary key does not exist");
}
Integer[] size = def.getSizes();
int recordSize = idxFixedRecordLength() + size[pkindex];
StringBuffer temp = new StringBuffer();
for (int i = 0; i < recordSize - 2; i++) {
temp.append(" ");
}
indexFile.seek(0);
for (int i = 0; i < this.hashsize; i++) {
indexFile.writeBytes(temp + "\r\n");
}
int table_pos = 0;
// create an index entry for each row present in the tbl-file (for column=colname)
String line = null;
tableFile.seek(0);
while ((line = tableFile.readLine()) != null) {
// get column value (don't strip the spaces)
String pkvalue = line.split("#")[pkindex];
addIndexEntry(table_pos, pkvalue);
table_pos++;
}
long e = System.currentTimeMillis();
return e - s;
}
/**
* Create an index entry in the idx file of the specified column.
*
* @param tablePosition position or line nr in table *.tbl
* @param pkValue the value of the primary key to create an index entry for
* @throws Exception
*/
protected void addIndexEntry(int tablePosition, String pkValue) throws Exception {
if (!indexExists(def.getPK())) {
throw new Exception("No index created");
}
int pkindex = def.getColPosition(def.getPK());
if (pkindex == -1) {
throw new Exception("Primary key does not exist");
}
Integer[] size = def.getSizes();
if (pkValue.length() > TableDefinition.INTEGER_SIZE) {
throw new Exception("Supplied pkValue too large");
} else {
// make sure key value has appropriate length
StringBuffer temp = new StringBuffer();
temp.append(pkValue);
for (int i = 0; i < TableDefinition.INTEGER_SIZE - pkValue.length(); i++) {
temp.append(' ');
}
pkValue = temp.toString();
}
// calculate index = hash value
String s_value = pkValue.trim();
int indexPosition = hash(s_value);
int recordSize = idxFixedRecordLength() + size[pkindex];
indexFile.seek(indexPosition * recordSize);
String line = indexFile.readLine();
if (line.substring(0, 1).equals(" ")) {
// empty record, reset file pointer and fill record
indexFile.seek(indexPosition * recordSize);
String indexPositionFormatted = String.format("%-5s", Integer.toString(indexPosition));
String tablePositionFormatted = String.format("%-5s", Integer.toString(tablePosition));
String indexRecord =
indexPositionFormatted
+ "# #"
+ pkValue
+ "#"
+ tablePositionFormatted
+ "#"
+ "null "
+ "\r\n";
indexFile.writeBytes(indexRecord);
} else {
String[] parts = line.split("#");
if (parts[1].equals("D")) {
// Deleted record, reset file pointer, fill record but keep previous link !
indexFile.seek(indexPosition * recordSize);
String indexPositionFormatted = String.format("%-5s", Integer.toString(indexPosition));
String tablePositionFormatted = String.format("%-5s", Integer.toString(tablePosition));
String indexRecord =
indexPositionFormatted + "# #" + pkValue + "#" + tablePositionFormatted;
indexFile.writeBytes(indexRecord);
} else {
// Collision found ! a valid record is found, so add new record at EOF
// Calculate new record number
int newIndexPosition = (int) (indexFile.length() / recordSize);
String newIndexPositionFormatted =
String.format("%-5s", Integer.toString(newIndexPosition));
String tablePositionFormatted = String.format("%-5s", Integer.toString(tablePosition));
// reset file pointer and update the current record
indexFile.seek((indexPosition * recordSize) + (recordSize - 2 - 5));
indexFile.write(newIndexPositionFormatted.toString().getBytes());
// move file pointer to EOF and append new record
indexFile.seek(indexFile.length());
String indexRecord =
newIndexPositionFormatted
+ "# #"
+ pkValue
+ "#"
+ tablePositionFormatted
+ "#"
+ "null "
+ "\r\n";
indexFile.writeBytes(indexRecord);
}
}
}
