/**
* Read a record from the database. Each field/value pair from the result will be stored in a
* HashMap.
*
* @param table The name of the table
* @param key The record key of the record to read.
* @param fields The list of fields to read, or null for all of them
* @param result A HashMap of field/value pairs for the result
* @return Zero on success, a non-zero error code on error
*/
public Status read(
String table, String key, Set<String> fields, HashMap<String, ByteIterator> result) {
// if this is a "new" table, init HTable object. Else, use existing one
if (!tableName.equals(table)) {
currentTable = null;
try {
getHTable(table);
tableName = table;
} catch (IOException e) {
System.err.println("Error accessing HBase table: " + e);
return Status.ERROR;
}
}
Result r = null;
try {
if (debug) {
System.out.println("Doing read from HBase columnfamily " + columnFamily);
System.out.println("Doing read for key: " + key);
}
Get g = new Get(Bytes.toBytes(key));
if (fields == null) {
g.addFamily(columnFamilyBytes);
} else {
for (String field : fields) {
g.addColumn(columnFamilyBytes, Bytes.toBytes(field));
}
}
r = currentTable.get(g);
} catch (IOException e) {
if (debug) {
System.err.println("Error doing get: " + e);
}
return Status.ERROR;
} catch (ConcurrentModificationException e) {
// do nothing for now...need to understand HBase concurrency model better
return Status.ERROR;
}
if (r.isEmpty()) {
return Status.NOT_FOUND;
}
while (r.advance()) {
final Cell c = r.current();
result.put(
Bytes.toString(CellUtil.cloneQualifier(c)),
new ByteArrayByteIterator(CellUtil.cloneValue(c)));
if (debug) {
System.out.println(
"Result for field: "
+ Bytes.toString(CellUtil.cloneQualifier(c))
+ " is: "
+ Bytes.toString(CellUtil.cloneValue(c)));
}
}
return Status.OK;
}
/**
* Perform a range scan for a set of records in the database. Each field/value pair from the
* result will be stored in a HashMap.
*
* @param table The name of the table
* @param startkey The record key of the first record to read.
* @param recordcount The number of records to read
* @param fields The list of fields to read, or null for all of them
* @param result A Vector of HashMaps, where each HashMap is a set field/value pairs for one
* record
* @return Zero on success, a non-zero error code on error
*/
@Override
public Status scan(
String table,
String startkey,
int recordcount,
Set<String> fields,
Vector<HashMap<String, ByteIterator>> result) {
// if this is a "new" table, init HTable object. Else, use existing one
if (!tableName.equals(table)) {
currentTable = null;
try {
getHTable(table);
tableName = table;
} catch (IOException e) {
System.err.println("Error accessing HBase table: " + e);
return Status.ERROR;
}
}
Scan s = new Scan(Bytes.toBytes(startkey));
// HBase has no record limit. Here, assume recordcount is small enough to
// bring back in one call.
// We get back recordcount records
s.setCaching(recordcount);
if (this.usePageFilter) {
s.setFilter(new PageFilter(recordcount));
}
// add specified fields or else all fields
if (fields == null) {
s.addFamily(columnFamilyBytes);
} else {
for (String field : fields) {
s.addColumn(columnFamilyBytes, Bytes.toBytes(field));
}
}
// get results
ResultScanner scanner = null;
try {
scanner = currentTable.getScanner(s);
int numResults = 0;
for (Result rr = scanner.next(); rr != null; rr = scanner.next()) {
// get row key
String key = Bytes.toString(rr.getRow());
if (debug) {
System.out.println("Got scan result for key: " + key);
}
HashMap<String, ByteIterator> rowResult = new HashMap<String, ByteIterator>();
while (rr.advance()) {
final Cell cell = rr.current();
rowResult.put(
Bytes.toString(CellUtil.cloneQualifier(cell)),
new ByteArrayByteIterator(CellUtil.cloneValue(cell)));
}
// add rowResult to result vector
result.add(rowResult);
numResults++;
// PageFilter does not guarantee that the number of results is <=
// pageSize, so this
// break is required.
if (numResults >= recordcount) { // if hit recordcount, bail out
break;
}
} // done with row
} catch (IOException e) {
if (debug) {
System.out.println("Error in getting/parsing scan result: " + e);
}
return Status.ERROR;
} finally {
if (scanner != null) {
scanner.close();
}
}
return Status.OK;
}
