How to use

getColumnNames

method

in

io.prestosql.orc.OrcReader

  private static Map<String, Integer> buildPhysicalNameOrdinalMap(OrcReader reader)
  {
    ImmutableMap.Builder<String, Integer> physicalNameOrdinalMap = ImmutableMap.builder();

    int ordinal = 0;
    for (String physicalColumnName : reader.getColumnNames()) {
      physicalNameOrdinalMap.put(physicalColumnName, ordinal);
      ordinal++;
    }

    return physicalNameOrdinalMap.build();
  }
}

private List<ColumnInfo> getColumnInfo(OrcReader reader)
{
  Optional<OrcFileMetadata> metadata = getOrcFileMetadata(reader);
  if (metadata.isPresent()) {
    return getColumnInfoFromOrcUserMetadata(metadata.get());
  }
  // support for legacy files without metadata
  return getColumnInfoFromOrcColumnTypes(reader.getColumnNames(), reader.getFooter().getTypes());
}

private static ColumnStats doComputeColumnStats(OrcReader orcReader, long columnId, Type type)
    throws IOException
{
  int columnIndex = columnIndex(orcReader.getColumnNames(), columnId);
  OrcRecordReader reader = orcReader.createRecordReader(ImmutableMap.of(columnIndex, type), OrcPredicate.TRUE, UTC, newSimpleAggregatedMemoryContext(), INITIAL_BATCH_SIZE);
  if (type.equals(BooleanType.BOOLEAN)) {
    return indexBoolean(type, reader, columnIndex, columnId);
  }
  if (type.equals(BigintType.BIGINT) ||
      type.equals(DateType.DATE) ||
      type.equals(TimestampType.TIMESTAMP)) {
    return indexLong(type, reader, columnIndex, columnId);
  }
  if (type.equals(DoubleType.DOUBLE)) {
    return indexDouble(type, reader, columnIndex, columnId);
  }
  if (type instanceof VarcharType) {
    return indexString(type, reader, columnIndex, columnId);
  }
  return null;
}

private static List<HiveColumnHandle> getPhysicalHiveColumnHandles(List<HiveColumnHandle> columns, boolean useOrcColumnNames, OrcReader reader, Path path)
{
  if (!useOrcColumnNames) {
    return columns;
  }
  verifyFileHasColumnNames(reader.getColumnNames(), path);
  Map<String, Integer> physicalNameOrdinalMap = buildPhysicalNameOrdinalMap(reader);
  int nextMissingColumnIndex = physicalNameOrdinalMap.size();
  ImmutableList.Builder<HiveColumnHandle> physicalColumns = ImmutableList.builder();
  for (HiveColumnHandle column : columns) {
    Integer physicalOrdinal = physicalNameOrdinalMap.get(column.getName());
    if (physicalOrdinal == null) {
      // if the column is missing from the file, assign it a column number larger
      // than the number of columns in the file so the reader will fill it with nulls
      physicalOrdinal = nextMissingColumnIndex;
      nextMissingColumnIndex++;
    }
    physicalColumns.add(new HiveColumnHandle(column.getName(), column.getHiveType(), column.getTypeSignature(), physicalOrdinal, column.getColumnType(), column.getComment()));
  }
  return physicalColumns.build();
}

OrcReader reader = new OrcReader(dataSource, ORC, readerAttributes.getMaxMergeDistance(), readerAttributes.getMaxReadSize(), readerAttributes.getTinyStripeThreshold(), HUGE_MAX_READ_BLOCK_SIZE);
Map<Long, Integer> indexMap = columnIdIndex(reader.getColumnNames());
ImmutableMap.Builder<Integer, Type> includedColumns = ImmutableMap.builder();
ImmutableList.Builder<Integer> columnIndexes = ImmutableList.builder();

public static OrcRecordReader createReader(OrcDataSource dataSource, List<Long> columnIds, List<Type> types)
    throws IOException
{
  OrcReader orcReader = new OrcReader(dataSource, ORC, new DataSize(1, MEGABYTE), new DataSize(1, MEGABYTE), new DataSize(1, MEGABYTE), new DataSize(1, MEGABYTE));
  List<String> columnNames = orcReader.getColumnNames();
  assertEquals(columnNames.size(), columnIds.size());
  Map<Integer, Type> includedColumns = new HashMap<>();
  int ordinal = 0;
  for (long columnId : columnIds) {
    assertEquals(columnNames.get(ordinal), String.valueOf(columnId));
    includedColumns.put(ordinal, types.get(ordinal));
    ordinal++;
  }
  return createRecordReader(orcReader, includedColumns);
}

public static OrcRecordReader createReaderNoRows(OrcDataSource dataSource)
    throws IOException
{
  OrcReader orcReader = new OrcReader(dataSource, ORC, new DataSize(1, MEGABYTE), new DataSize(1, MEGABYTE), new DataSize(1, MEGABYTE), new DataSize(1, MEGABYTE));
  assertEquals(orcReader.getColumnNames().size(), 0);
  return createRecordReader(orcReader, ImmutableMap.of());
}

validateWrite(validation -> validation.getColumnNames().equals(getColumnNames()), "Unexpected column names");
validateWrite(validation -> validation.getRowGroupMaxRowCount() == footer.getRowsInRowGroup(), "Unexpected rows in group");
if (writeValidation.isPresent()) {

validateWrite(validation -> validation.getColumnNames().equals(getColumnNames()), "Unexpected column names");
validateWrite(validation -> validation.getRowGroupMaxRowCount() == footer.getRowsInRowGroup(), "Unexpected rows in group");
if (writeValidation.isPresent()) {