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Trino - Kudu Connector
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/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.trino.plugin.kudu;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import io.airlift.slice.Slice;
import io.airlift.slice.Slices;
import io.trino.spi.connector.RecordCursor;
import io.trino.spi.type.Type;
import org.apache.kudu.client.KeyEncoderAccessor;
import org.apache.kudu.client.KuduException;
import org.apache.kudu.client.KuduScanner;
import org.apache.kudu.client.KuduScannerIterator;
import org.apache.kudu.client.KuduTable;
import org.apache.kudu.client.PartialRow;
import org.apache.kudu.client.RowResult;

import java.util.List;
import java.util.Map;

import static io.trino.plugin.kudu.KuduColumnHandle.ROW_ID_POSITION;
import static java.util.Objects.requireNonNull;

public class KuduRecordCursor
        implements RecordCursor
{
    private final KuduScanner scanner;
    private final List columnTypes;
    private final KuduTable table;
    private final Map fieldMapping;
    private final KuduScannerIterator kuduScannerIterator;
    private RowResult currentRow;

    private long totalBytes;

    private volatile boolean closed;

    public KuduRecordCursor(KuduScanner scanner, KuduTable table, List columnTypes, Map fieldMapping)
    {
        this.scanner = requireNonNull(scanner, "scanner is null");
        this.columnTypes = ImmutableList.copyOf(requireNonNull(columnTypes, "columnTypes is null"));
        this.table = requireNonNull(table, "table is null");
        this.fieldMapping = ImmutableMap.copyOf(requireNonNull(fieldMapping, "fieldMapping is null"));
        kuduScannerIterator = scanner.iterator();
    }

    @Override
    public long getCompletedBytes()
    {
        return totalBytes;
    }

    @Override
    public long getReadTimeNanos()
    {
        return 0;
    }

    @Override
    public Type getType(int field)
    {
        return columnTypes.get(field);
    }

    private int mapping(int field)
    {
        return fieldMapping.get(field);
    }

    /**
     * get next Row/Page
     */
    @Override
    public boolean advanceNextPosition()
    {
        if (!kuduScannerIterator.hasNext()) {
            closed = scanner.isClosed();
            return false;
        }

        currentRow = kuduScannerIterator.next();
        totalBytes += getRowLength();
        return true;
    }

    private int getRowLength()
    {
        return currentRow.getSchema().getRowSize();
    }

    @Override
    public boolean getBoolean(int field)
    {
        int index = mapping(field);
        return TypeHelper.getBoolean(columnTypes.get(field), currentRow, index);
    }

    @Override
    public long getLong(int field)
    {
        int index = mapping(field);
        return TypeHelper.getLong(columnTypes.get(field), currentRow, index);
    }

    @Override
    public double getDouble(int field)
    {
        int index = mapping(field);
        return TypeHelper.getDouble(columnTypes.get(field), currentRow, index);
    }

    @Override
    public Slice getSlice(int field)
    {
        int index = mapping(field);
        if (index == ROW_ID_POSITION) {
            PartialRow partialRow = buildPrimaryKey();
            return Slices.wrappedBuffer(KeyEncoderAccessor.encodePrimaryKey(partialRow));
        }
        return TypeHelper.getSlice(columnTypes.get(field), currentRow, index);
    }

    @Override
    public Object getObject(int field)
    {
        int index = mapping(field);
        return TypeHelper.getObject(columnTypes.get(field), currentRow, index);
    }

    @Override
    public boolean isNull(int field)
    {
        int mappedField = mapping(field);
        return mappedField >= 0 && currentRow.isNull(mappedField);
    }

    private PartialRow buildPrimaryKey()
    {
        PartialRow row = new PartialRow(table.getSchema());
        RowHelper.copyPrimaryKey(table.getSchema(), currentRow, row);
        return row;
    }

    @Override
    public void close()
    {
        if (!closed) {
            try {
                scanner.close();
            }
            catch (KuduException e) {
                throw new RuntimeException(e);
            }
            finally {
                currentRow = null;
                closed = true;
            }
        }
    }
}