@Override
public List<?> translateCommand(Command command, ExecutionContext context) {
if (command instanceof Insert) {
try {
handleInsertSequences((Insert) command);
} catch (TranslatorException e) {
throw new RuntimeException(e);
}
}
if (!(command instanceof QueryExpression)) {
return null;
}
QueryExpression queryCommand = (QueryExpression) command;
if (queryCommand.getLimit() == null) {
return null;
}
Limit limit = queryCommand.getLimit();
queryCommand.setLimit(null);
if (command instanceof Select) {
Select select = (Select) command;
TableReference tr = select.getFrom().get(0);
if (tr instanceof NamedTable && isDual((NamedTable) tr)) {
if (limit.getRowOffset() > 0 || limit.getRowLimit() == 0) {
// no data
select.setWhere(
new Comparison(
new Literal(1, TypeFacility.RUNTIME_TYPES.INTEGER),
new Literal(0, TypeFacility.RUNTIME_TYPES.INTEGER),
Operator.EQ));
return null;
}
return null; // dual does not allow a limit
}
}
List<Object> parts = new ArrayList<Object>();
parts.add("SELECT "); // $NON-NLS-1$
/*
* if all of the columns are aliased, assume that names matter - it actually only seems to matter for
* the first query of a set op when there is a order by. Rather than adding logic to traverse up,
* we just use the projected names
*/
boolean allAliased = true;
for (DerivedColumn selectSymbol : queryCommand.getProjectedQuery().getDerivedColumns()) {
if (selectSymbol.getAlias() == null) {
allAliased = false;
break;
}
}
if (allAliased) {
String[] columnNames = queryCommand.getColumnNames();
for (int i = 0; i < columnNames.length; i++) {
if (i > 0) {
parts.add(", "); // $NON-NLS-1$
}
parts.add(columnNames[i]);
}
} else {
parts.add("*"); // $NON-NLS-1$
}
if (limit.getRowOffset() > 0) {
parts.add(" FROM (SELECT VIEW_FOR_LIMIT.*, ROWNUM ROWNUM_ FROM ("); // $NON-NLS-1$
} else {
parts.add(" FROM ("); // $NON-NLS-1$
}
parts.add(queryCommand);
if (limit.getRowOffset() > 0) {
parts.add(") VIEW_FOR_LIMIT WHERE ROWNUM <= "); // $NON-NLS-1$
parts.add(limit.getRowLimit() + limit.getRowOffset());
parts.add(") WHERE ROWNUM_ > "); // $NON-NLS-1$
parts.add(limit.getRowOffset());
} else {
parts.add(") WHERE ROWNUM <= "); // $NON-NLS-1$
parts.add(limit.getRowLimit());
}
return parts;
}
