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 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2022 QuestDB
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 *  you may not use this file except in compliance with the License.
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 *  http://www.apache.org/licenses/LICENSE-2.0
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 *  distributed under the License is distributed on an "AS IS" BASIS,
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package io.questdb.cairo.sql;

import io.questdb.cairo.TableReader;
import org.jetbrains.annotations.Nullable;

import java.io.Closeable;

/**
 * A cursor for managing position of operations within data frames
 *
 * Interfaces which extend Closeable are not optionally-closeable.
 * close() method must be called after other calls are complete.
 */
public interface DataFrameCursor extends Closeable, SymbolTableSource  {

    // same TableReader is available on each data frame
    TableReader getTableReader();

    /**
     * Reload the data frame and return the cursor to the beginning of
     * the data frame
     * @return true when reload data has changed, false otherwise
     */
    boolean reload();

    /**
     * @return the next element in the data frame
     */
    @Nullable DataFrame next();

    /**
     * Must be closed after other calls are complete
     */
    @Override
    void close();

    /**
     * Return the cursor to the beginning of the data frame
     */
    void toTop();

    /**
     * @return number of items in the data frame
     */
    long size();

    StaticSymbolTable getSymbolTable(int columnIndex);

    StaticSymbolTable newSymbolTable(int columnIndex);

    /**
     * @return  true if cursor supports random record access (without having to iterate through all results).
     */
    default boolean supportsRandomAccess() {
        return false;
    }

    /**
     * Positions data frame at the given row number.
     *
     * @param rowCount absolute row number in table. Rows are numbered 0...row_count-1
     *
     * @return data frame and position (lo) of given rowCount (according to cursor order) .
     */
    default @Nullable DataFrame skipTo(long rowCount) {
        throw new UnsupportedOperationException();
    }
}