/*
* Gets the ColumnType from the given FieldSchema by using Impala's SqlParser.
* Returns null if the FieldSchema could not be parsed.
* The type can either be:
* - Supported by Impala, in which case the type is returned.
* - A type Impala understands but is not yet implemented (e.g. date), the type is
* returned but type.IsSupported() returns false.
* - A type Impala can't understand at all in which case null is returned.
*/
public static ColumnType parseColumnType(FieldSchema fs) {
// Wrap the type string in a CREATE TABLE stmt and use Impala's Parser
// to get the ColumnType.
// Pick a table name that can't be used.
String stmt = String.format("CREATE TABLE $DUMMY ($DUMMY %s)", fs.getType());
SqlScanner input = new SqlScanner(new StringReader(stmt));
SqlParser parser = new SqlParser(input);
CreateTableStmt createTableStmt;
try {
Object o = parser.parse().value;
if (!(o instanceof CreateTableStmt)) {
// Should never get here.
throw new IllegalStateException("Couldn't parse create table stmt.");
}
createTableStmt = (CreateTableStmt) o;
if (createTableStmt.getColumnDescs().isEmpty()) {
// Should never get here.
throw new IllegalStateException("Invalid create table stmt.");
}
} catch (Exception e) {
return null;
}
return createTableStmt.getColumnDescs().get(0).getColType();
}
