JDBCDataSource.java

package com.upsolver.datasources.jdbc;

import com.upsolver.common.datasources.DataLoader;
import com.upsolver.common.datasources.DataSourceContentType;
import com.upsolver.common.datasources.DataSourceDescription;
import com.upsolver.common.datasources.ExternalDataSource;
import com.upsolver.common.datasources.LoadedData;
import com.upsolver.common.datasources.PropertyDescription;
import com.upsolver.common.datasources.PropertyEditor;
import com.upsolver.common.datasources.PropertyError;
import com.upsolver.common.datasources.ShardDefinition;
import com.upsolver.common.datasources.SimplePropertyDescription;
import com.upsolver.common.datasources.TaskInformation;
import com.upsolver.common.datasources.TaskRange;
import com.upsolver.common.datasources.contenttypes.CSVContentType;
import com.upsolver.common.datasources.contenttypes.JsonDataSourceContentType;
import com.upsolver.datasources.jdbc.metadata.ColumnInfo;
import com.upsolver.datasources.jdbc.metadata.TableInfo;
import com.upsolver.datasources.jdbc.querybuilders.QueryDialect;
import com.upsolver.datasources.jdbc.querybuilders.QueryDialectProvider;
import com.upsolver.datasources.jdbc.utils.NamedPreparedStatment;
import com.upsolver.datasources.jdbc.utils.SQLDriver;
import com.upsolver.datasources.jdbc.utils.SQLDrivers;
import com.zaxxer.hikari.HikariDataSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.StringReader;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.time.Instant;
import java.time.temporal.ChronoUnit;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Properties;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.atomic.AtomicReference;
import java.util.stream.Collectors;

import static com.upsolver.datasources.jdbc.utils.MarkdownEscaper.escape;
import static java.lang.String.format;

public class JDBCDataSource implements ExternalDataSource<JDBCTaskMetadata, JDBCTaskMetadata> {


    private final Logger logger = LoggerFactory.getLogger(this.getClass());


    private static final String connectionStringProp = "Connection String";
    private static final String connectionPropertiesProp = "Connection Properties";
    private static final String schemaPatternProp = "Schema Pattern";
    private static final String tableNameProp = "Table Name";
    private static final String incrementingColumnNameProp = "Incrementing Column";
    private static final String timestampColumnsProp = "Timestamp Columns";
    private static final String readDelayProp = "Read Delay";
    private static final String fullLoadIntervalProp = "Full Load Interval";
    private static final String loadIntervalProp = "Incremental Load Interval";
    private static final String userNameProp = "User Name";
    private static final String passwordProp = "Password";
    private static final String keepSourceTypes = "Keep JDBC source types";
    private static final SQLDrivers sqlDrivers = new SQLDrivers();
    private static final List<PropertyDescription> propertyDescriptions =
            Arrays.asList(
                    new SimplePropertyDescription(connectionStringProp, "The connection string that will be used to connect to the database", false),
                    new SimplePropertyDescription(connectionPropertiesProp, "Extra connection properties that will be used to connect to the database", true, false, new String[0], null, PropertyEditor.TEXT_AREA),
                    new SimplePropertyDescription(userNameProp, "The user name to connect with", false),
                    new SimplePropertyDescription(passwordProp, "The password to connect with", false, true),
                    new SimplePropertyDescription(schemaPatternProp, "A schema name pattern; must match the schema name as it is stored in the database; \"\" retrieves those without a schema; empty means that the schema name should not be used to narrow the search for the table", true),
                    new SimplePropertyDescription(tableNameProp, "The name of the table to read from", false),
                    new SimplePropertyDescription(incrementingColumnNameProp, "The name of the column which has an incrementing value to be used to load data sequentially", true),
                    new SimplePropertyDescription(timestampColumnsProp, "Comma separated list of timestamp columns to use for loading new rows. The fist non-null value will be used. At least one of the values must not be null for each row", true),
                    new SimplePropertyDescription(readDelayProp, "How long (in seconds) to wait before reading rows based on their timestamp. This allows waiting for all transactions of a certain timestamp to complete to avoid loading partial data. Default value is 0", true),
                    new SimplePropertyDescription(fullLoadIntervalProp, "If set the full table will be read every configured interval (in minutes). When this is configured the update time and incrementing columns are not used.", true),
                    new SimplePropertyDescription(keepSourceTypes, "Keep original data types from source to use string representation", true, false, null, null, null, true, Optional.of("true")),
                    new SimplePropertyDescription(loadIntervalProp, "Configures how often (in minutes) the data source will poll the database for new changes", true));

    private long readDelay;
    private long fullLoadIntervalMinutes;
    private long loadIntervalMinutes;
    private TableInfo tableInfo;
    private QueryDialect queryDialect;
    private long dbTimezoneOffset;
    private long overallQueryTimeAdjustment;
    private boolean keepTypes = false;
    private DataSourceContentType contentType;
    private RowConverter rowConverter;


    private final int connectionIdleTimeout = 90 * 1000;
    private HikariDataSource ds = null;

    private boolean isFullLoad() {
        return fullLoadIntervalMinutes > 0;
    }

    private boolean hasCustomLoadInterval() {
        return loadIntervalMinutes > 1;
    }

    @Override
    public DataSourceDescription getDataSourceDescription() {
        return new JDBCDataSourceDescription();
    }

    @Override
    public int getMaxShards() {
        return 1;
    }

    @Override
    public void setProperties(Map<String, String> properties) {
        ds = new HikariDataSource();
        String connectionString = properties.get(connectionStringProp);
        ds.setMaximumPoolSize(1);
        ds.setIdleTimeout(connectionIdleTimeout);
        ds.setMinimumIdle(0);
        String connectionProperties = properties.getOrDefault(connectionPropertiesProp, "");
        if (!connectionProperties.isBlank()) {
            Properties props = new Properties();
            try {
                props.load(new StringReader(connectionProperties));
                ds.setDataSourceProperties(props);
            } catch (IOException e) {
                logger.error("Unable to parse connection properties", e);
                throw new RuntimeException("Unable to parse connection properties: '" + connectionProperties + "'", e);
            }
        }
        ds.setJdbcUrl(connectionString);
        ds.setUsername(properties.get(userNameProp));
        ds.setPassword(properties.get(passwordProp));
        keepTypes = Optional.ofNullable(properties.get(keepSourceTypes)).map(Boolean::parseBoolean).orElse(false);
        contentType = keepTypes ? new JsonDataSourceContentType() : new CSVContentType(true, ',', null, null);

        queryDialect = QueryDialectProvider.forConnection(connectionString, keepTypes);
        String driverClassName = queryDialect.getDriverClassName();
        if (driverClassName != null) {
            ds.setDriverClassName(driverClassName);
        }

        try (Connection con = getConnection()) {
            readDelay = Long.parseLong(properties.getOrDefault(readDelayProp, "0"));
            fullLoadIntervalMinutes = Long.parseLong(properties.getOrDefault(fullLoadIntervalProp, "0"));
            loadIntervalMinutes = Long.parseLong(properties.getOrDefault(loadIntervalProp, "1"));
            DatabaseMetaData metadata = con.getMetaData();
            String userProvidedIncColumn = properties.get(incrementingColumnNameProp);
            tableInfo = loadTableInfo(metadata, properties.getOrDefault(schemaPatternProp, null), properties.get(tableNameProp));
            rowConverter = keepTypes ? new JsonRowConverter(tableInfo) : new CsvRowConverter(tableInfo);
            var allTimeColumns = new HashSet<String>();
            if (userProvidedIncColumn != null) {
                tableInfo.setIncColumn(queryDialect.toUpperCaseIfRequired(userProvidedIncColumn));
            }
            for (ColumnInfo column : tableInfo.getColumns()) {
                if (column.isTimeType()) {
                    allTimeColumns.add(column.getName().toUpperCase());
                } else if (tableInfo.getIncColumn() == null && column.isIncCol()) {
                    tableInfo.setIncColumn(queryDialect.toUpperCaseIfRequired(column.getName()));
                }
            }
            String[] filteredTimestampColumns =
                    Arrays.stream(properties.getOrDefault(timestampColumnsProp, "").split(","))
                            .map(String::trim)
                            .filter(x -> allTimeColumns.contains(x.toUpperCase()))
                            .map(f -> queryDialect.toUpperCaseIfRequired(f))
                            .toArray(String[]::new);
            if (filteredTimestampColumns.length != 0) {
                tableInfo.setTimeColumns(filteredTimestampColumns);
            }
            dbTimezoneOffset = queryDialect.utcOffsetSeconds(con);
            overallQueryTimeAdjustment = dbTimezoneOffset - readDelay;
        } catch (Exception e) {
            throw new RuntimeException("Unable to set configuration: " + connectionString + "'", e);
        }
    }

    @Override
    public Instant getStartTime() {
        if (isFullLoad()) {
            return Instant.now().minus(fullLoadIntervalMinutes, ChronoUnit.MINUTES);
        } else if (tableInfo.hasTimeColumns()) {
            try {
                return queryDialect.getStartTime(tableInfo, getConnection());
            } catch (SQLException error) {
                logger.error("Error while getting start time, returning null (start from now)", error);
                return null;
            }
        } else {
            return null;
        }
    }

    private String[] getSupportedTableTypes(DatabaseMetaData metaData) throws SQLException {
        var result = new ArrayList<String>();
        var rs = metaData.getTableTypes();
        while (rs.next()) {
            var type = rs.getString("TABLE_TYPE").toUpperCase();
            if (type.equals("TABLE") || type.equals("VIEW")) {
                result.add(type);
            }
        }
        String[] arr = new String[result.size()];
        return result.toArray(arr);
    }

    private TableInfo loadTableInfo(DatabaseMetaData metadata, String schemaPattern, String tableName) throws SQLException {
        var fixedTableName = queryDialect.toUpperCaseIfRequired(tableName);
        var fixedSchemaPattern = queryDialect.toUpperCaseIfRequired(schemaPattern);
        var supportedTableTypes = getSupportedTableTypes(metadata);
        var tables = metadata.getTables(null, fixedSchemaPattern, fixedTableName, supportedTableTypes);
        if (tables.next()) {
            var columns = new ArrayList<ColumnInfo>();
            String catalog = tables.getString(1);
            String schema = tables.getString(2);
            String dbTableName = tables.getString(3);

            var columnRs = metadata.getColumns(catalog, schema, dbTableName, null);
            while (columnRs.next()) {
                String colName = columnRs.getString("COLUMN_NAME");
                int type = columnRs.getInt("DATA_TYPE");
                var sqlType = queryDialect.getSqlType(type);
                columns.add(new ColumnInfo(colName, sqlType, queryDialect.isAutoIncrementColumn(columnRs), queryDialect.isTimeType(sqlType)));
            }

            return new TableInfo(catalog, schema, dbTableName, columns.toArray(ColumnInfo[]::new));
        } else {
            throw new IllegalArgumentException("Could not find table with name: " + fixedTableName);
        }

    }

    @Override
    public List<PropertyDescription> getPropertyDescriptions() {
        return propertyDescriptions;
    }

    @Override
    public DataSourceContentType getContentType() {
        return contentType;
    }

    @Override
    public CompletionStage<LoadedData> getSample() {
        JDBCTaskMetadata sampleMetadata =
                new JDBCTaskMetadata(0L, Long.MAX_VALUE, Instant.EPOCH, toQueryTime(Instant.now()));
        Connection connection = getConnection();
        var result = queryData(sampleMetadata, 100, connection, true);
        var rowReader =
                new RowReader(tableInfo, new ResultSetValuesGetter(tableInfo, result, queryDialect), sampleMetadata, connection, true);
        var inputStream = new ResultSetInputStream(rowConverter, rowReader, true);
        var loadedData = new LoadedData(inputStream, Instant.now());
        return CompletableFuture.completedFuture(loadedData);
    }

    private Connection getConnection() {
        try {
            return ds.getConnection();
        } catch (SQLException e) {
            throw new RuntimeException("Failed to get connection", e);
        }
    }

    private Instant toQueryTime(Instant time) {
        return time.plusSeconds(overallQueryTimeAdjustment);
    }

    private Instant toUtc(Instant time) {
        return time.minusSeconds(dbTimezoneOffset);
    }

    private ResultSet queryData(JDBCTaskMetadata metadata, int limit, Connection connection, boolean isSample) {
        try {
            if (isSample || isFullLoad()) {
                return queryDialect.queryFullTable(tableInfo, metadata, limit, connection).executeQuery();
            } else if (tableInfo.hasTimeColumns()) {
                if (tableInfo.getIncColumn() != null) {
                    return queryDialect.queryByIncAndTime(tableInfo, metadata, limit, connection).executeQuery();
                } else {
                    return this.queryDialect.queryByTime(this.tableInfo, metadata, limit, connection).executeQuery();
                }
            } else {
                return queryDialect.queryByInc(tableInfo, metadata, limit, connection).executeQuery();
            }
        } catch (Exception e) {
            try {
                connection.close();
            } catch (SQLException closeException) {
                logger.error("Could not close connection", closeException);
            }
            logger.error("Error reading table", e);
            throw new RuntimeException("Error while reading table", e);
        }
    }

    @Override
    public List<PropertyError> validate(Map<String, String> properties) {
        var connectionString = properties.get(connectionStringProp);
        var connectionProperties = properties.getOrDefault(connectionPropertiesProp, "");
        var user = properties.get(userNameProp);
        var pass = properties.get(passwordProp);
        var timestampColString = properties.get(timestampColumnsProp);
        queryDialect = QueryDialectProvider.forConnection(connectionString, keepTypes);
        var fullLoad = !properties.getOrDefault(fullLoadIntervalProp, "0").equals("0");
        var timestampCols =
                timestampColString != null ?
                        Arrays.stream(timestampColString.split(",")).map(String::trim).toArray(String[]::new) : new String[0];
        var connectionProps = new Properties();
        if (!connectionProperties.isBlank()) {
            try {
                connectionProps.load(new StringReader(connectionProperties));
            } catch (IOException e) {
                return Collections.singletonList(new PropertyError(connectionPropertiesProp, "Unable to parse connection properties: \n" + e.getMessage()));
            }
        }
        connectionProps.setProperty("user", connectionProps.getProperty("user", user));
        connectionProps.setProperty("password", connectionProps.getProperty("password", pass));

        try (var connection = queryDialect.getConnection(connectionString, connectionProps)) {
            return validateTableInfo(connection,
                    properties.getOrDefault(schemaPatternProp, null),
                    properties.get(tableNameProp),
                    properties.get(incrementingColumnNameProp),
                    timestampCols,
                    fullLoad);
        } catch (SQLException e) {
            Collection<SQLDriver> suitableDrivers = sqlDrivers.getDrivers().stream().filter(driver -> connectionString.startsWith(driver.getUrlPrefix())).collect(Collectors.toList());
            final String errorMessage;
            if (suitableDrivers.isEmpty()) {
                logger.info("Unable to connect to database, using JDBC URL: {}", connectionString, e);
                String msg = sqlDrivers.getDrivers().stream().map(driver -> format("%s (%s)", driver.getName(), driver.getUrlPrefix()))
                        .collect(Collectors.joining("   \n"));
                errorMessage = format("Unable to connect to database, the following databases are supported:   \n %s ", msg);
            } else {
                String urlTemplates = suitableDrivers.stream().map(SQLDriver::getUrlTemplate).collect(Collectors.joining(", "));
                errorMessage = format("Unable to connect to database, please ensure connection string (%s) and login info is correct.  \n SqlError: %s.  \nConnection string should look like %s",
                        connectionString,
                        e.getMessage(),
                        urlTemplates);
            }
            return Collections.singletonList(new PropertyError(connectionStringProp, escape(errorMessage)));
        }
    }

    private List<PropertyError> validateTableInfo(Connection connection,
                                                  String schemaPattern,
                                                  String tableName,
                                                  String incColumn,
                                                  String[] timestampColumns,
                                                  boolean fullLoad) {
        var result = new ArrayList<PropertyError>();

        try {
            var connectionMetadata = connection.getMetaData();
            // Always load table info to confirm table exists
            var tableInfo = loadTableInfo(connectionMetadata, schemaPattern, tableName);
            if (!fullLoad) {
                if (incColumn != null) {
                    var autoInc = tableInfo.getColumn(incColumn);
                    if (autoInc == null) {
                        result.add(new PropertyError(incrementingColumnNameProp, "Could not find increment column " + incColumn));
                    } else if (!autoInc.isIncCol()) {
                        result.add(new PropertyError(incrementingColumnNameProp, "Column " + incColumn + " is not an auto-inc column"));
                    }
                }
                var foundTimeCol = false;
                for (String timestampColumn : timestampColumns) {
                    var col = tableInfo.getColumn(timestampColumn);
                    if (col != null) {
                        if (col.isTimeType()) {
                            foundTimeCol = true;
                        } else {
                            result.add(new PropertyError(timestampColumnsProp, "Column '" + timestampColumn + "' is not a timestamp columns"));
                        }
                    }
                }
                if (timestampColumns.length > 0 && !foundTimeCol) {
                    result.add(new PropertyError(timestampColumnsProp, "Non of the provided timestamp columns exist in the table"));
                }
                if (timestampColumns.length == 0) {
                    if (Arrays.stream(tableInfo.getColumns()).noneMatch(ColumnInfo::isIncCol)) {
                        result.add(new PropertyError(timestampColumnsProp,
                                "The table has no auto-incrementing column, you must provide update time columns to use"));
                    }
                }
            }
        } catch (IllegalArgumentException e) {
            result.add(new PropertyError(tableNameProp, "Could not load table with name: '" + tableName + "'. " + e.getMessage()));
        } catch (SQLException e) {
            throw new RuntimeException("Failed to get table info", e);
        }

        return result;
    }

    @Override
    public CompletionStage<Iterator<DataLoader<JDBCTaskMetadata>>> getDataLoaders(TaskInformation<JDBCTaskMetadata> taskInfo,
                                                                                  List<TaskRange> completedRanges,
                                                                                  List<TaskRange> wantedRanges,
                                                                                  Optional<JDBCTaskMetadata> optional,
                                                                                  ShardDefinition shardDefinition) {

        var taskCount = completedRanges.size() + wantedRanges.size();
        var itemsPerTask = (taskInfo.getMetadata().itemsPerTask(taskCount));
        var skipAll = hasCustomLoadInterval() && wantedRanges.stream().noneMatch(this::matchesLoadInterval);
        var emptyFullLoad = isFullLoad() && wantedRanges.stream().noneMatch(this::matchesFullLoadInterval);
        var noDataToLoad = !isFullLoad() && !tableInfo.hasTimeColumns() && itemsPerTask == 0;
        if (skipAll || emptyFullLoad || noDataToLoad) {
            List<DataLoader<JDBCTaskMetadata>> result =
                    wantedRanges.stream().map(t -> new NoDataLoader(t, taskInfo.getMetadata())).collect(Collectors.toList());
            return CompletableFuture.completedFuture(result.iterator());
        } else {
            var runMetadatas = getRunMetadatas(taskInfo, taskCount, itemsPerTask, wantedRanges);
            var firstMetadata = runMetadatas.get(0);
            var lastMetadata = runMetadatas.get(runMetadatas.size() - 1);
            var queryMetadata = new JDBCTaskMetadata(firstMetadata.getInclusiveStart(), lastMetadata.getExclusiveEnd(),
                    firstMetadata.getStartTime(), lastMetadata.getEndTime())
                    .adjustWithDelay(dbTimezoneOffset);
            var connection = getConnection();
            var resultSet = queryData(queryMetadata, -1, connection, false);
            return splitData(resultSet, wantedRanges, runMetadatas, connection);
        }
    }

    private boolean matchesFullLoadInterval(TaskRange x) {
        return getTimeInMinutes(x.getInclusiveStartTime()) % fullLoadIntervalMinutes == 0;
    }

    private boolean matchesLoadInterval(TaskRange x) {
        return getTimeInMinutes(x.getInclusiveStartTime()) % loadIntervalMinutes == 0;
    }

    private Long getTimeInMinutes(Instant time) {
        return time.getEpochSecond() / 60L;
    }

    private List<JDBCTaskMetadata> getRunMetadatas(TaskInformation<JDBCTaskMetadata> taskInfo,
                                                   int taskCount,
                                                   double itemsPerTask,
                                                   List<TaskRange> wantedRanges) {
        var result = new ArrayList<JDBCTaskMetadata>();
        int wantedSize = wantedRanges.size();
        var wantedIndexStart = taskCount - wantedSize;
        if (isFullLoad()) {
            return wantedRanges.stream()
                    .map(wr -> new JDBCTaskMetadata(0, 0, wr.getInclusiveStartTime(), wr.getExclusiveEndTime()))
                    .collect(Collectors.toList());
        } else if (tableInfo.hasTimeColumns()) {
            for (int i = 0; i < wantedSize; i++) {
                var firstInBatch = i == 0 && taskCount == wantedSize;
                TaskRange wantedRange = wantedRanges.get(i);
                // First task does not have lower bound to ensure we don't skip data from the last point we stopped at
                var startTime =
                        firstInBatch ? taskInfo.getMetadata().getStartTime() : wantedRange.getInclusiveStartTime().minusSeconds(readDelay);
                var lowerBound = taskInfo.getMetadata().getStartTime().getEpochSecond();
                var truncatedStartTime = Math.max(lowerBound, hasCustomLoadInterval() ?
                        (getTimeInMinutes(startTime) / loadIntervalMinutes * 60 * loadIntervalMinutes)
                        : startTime.getEpochSecond());
                var endTime = wantedRange.getExclusiveEndTime().minusSeconds(readDelay);
                var truncatedEndTime = Math.max(lowerBound,hasCustomLoadInterval() ?
                        getTimeInMinutes(endTime) / loadIntervalMinutes * 60 * loadIntervalMinutes
                        : endTime.getEpochSecond());
                var metadata = new JDBCTaskMetadata(taskInfo.getMetadata().getInclusiveStart(),
                        taskInfo.getMetadata().getExclusiveEnd(),
                        Instant.ofEpochSecond(truncatedStartTime),
                        Instant.ofEpochSecond(truncatedEndTime));
                result.add(metadata);
            }
        } else {
            var start = (double) taskInfo.getMetadata().getInclusiveStart();
            // Make sure to iterate the full task count and not just wantedRanges.size() to avoid rounding error differences
            // between executions with different amounts of wantedRanges
            for (int i = 0; i < taskCount; i++) {
                var endValue = start + itemsPerTask;
                // Due to rounding of values make sure the last task gets everything remaining
                if (i == taskCount - 1) endValue = Math.max(endValue, taskInfo.getMetadata().getExclusiveEnd());
                var metadata = new JDBCTaskMetadata((long) start, (long) endValue, Instant.MIN, JDBCTaskMetadata.initalEndTime);
                if (i >= wantedIndexStart) {
                    result.add(metadata);
                }
                start = endValue;
            }
        }
        return result;
    }


    private CompletionStage<Iterator<DataLoader<JDBCTaskMetadata>>> splitData(ResultSet resultSet,
                                                                              List<TaskRange> wantedRanges,
                                                                              List<JDBCTaskMetadata> runMetadatas,
                                                                              Connection connection) {
        var result = new ArrayList<DataLoader<JDBCTaskMetadata>>();
        var lastReadIncValue = new AtomicReference<>(runMetadatas.get(0).getInclusiveStart());
        var lastReadTime = new AtomicReference<>(runMetadatas.get(0).getStartTime());

        // Value getter + Some of the code in RowReader are needed only because we insist on running a single query
        // and using a single result set for all ranges. If we allow query per window a lot of the code can be simplified.
        var valueGetter = new ResultSetValuesGetter(tableInfo, resultSet, queryDialect);

        for (int i = 0; i < wantedRanges.size(); i++) {
            final var isLast = i == wantedRanges.size() - 1;
            final var taskRange = wantedRanges.get(i);
            final var metadata = runMetadatas.get(i);
            DataLoader<JDBCTaskMetadata> loader = null;
                    if (matchesLoadInterval(taskRange)){
                        loader = getLoader(connection,
                                lastReadIncValue,
                                lastReadTime,
                                valueGetter,
                                isLast,
                                taskRange,
                                metadata);
                    } else {
                        loader = new NoDataLoader(taskRange, metadata);
                    }
            result.add(loader);

        }
        return CompletableFuture.completedFuture(result.iterator());

    }

    private DataLoader<JDBCTaskMetadata> getLoader(Connection connection, AtomicReference<Long> lastReadIncValue, AtomicReference<Instant> lastReadTime, ResultSetValuesGetter valueGetter, boolean isLast, TaskRange taskRange, JDBCTaskMetadata metadata) {
        return new DataLoader<JDBCTaskMetadata>() {
            @Override
            public TaskRange getTaskRange() {
                return taskRange;
            }

            private final RowReader rowReader = new RowReader(tableInfo, valueGetter, metadata, connection, isFullLoad() && matchesFullLoadInterval(taskRange));

            @Override
            public Iterator<LoadedData> loadData() {
                ResultSetInputStream inputStream = new ResultSetInputStream(rowConverter, rowReader, isLast);
                var result = new LoadedData(inputStream, new HashMap<>(), taskRange.getInclusiveStartTime());
                return Collections.singleton(result).iterator();
            }

            @Override
            public JDBCTaskMetadata getCompletedMetadata() {
                if (tableInfo.hasTimeColumns() && rowReader.readValues()) {
                    if (rowReader.readValues()) {
                        // If some data was successfully read then that's our next start point
                        lastReadTime.set(toUtc(rowReader.getLastTimestampValue().toInstant()));
                        lastReadIncValue.set(rowReader.getLastIncValue());
                    }
                    metadata.setExclusiveEnd(lastReadIncValue.get() + 1);
                    metadata.setEndTime(lastReadTime.get());
                }

                return metadata;
            }
        };
    }


    @Override
    public CompletionStage<TaskInformation<JDBCTaskMetadata>> getTaskInfo(JDBCTaskMetadata previousTaskMetadata,
                                                                          TaskRange taskRange,
                                                                          ShardDefinition shardDefinition) {
        var previous = previousTaskMetadata != null ?
                previousTaskMetadata : new JDBCTaskMetadata(0, 0);
        var startFrom = previous.getExclusiveEnd();
        try (var connection = getConnection(); var statement = getTaskInfoQuery(previous, taskRange, connection)) {
            var rs = statement.executeQuery();
            if (rs.next()) {
                var max = tableInfo.hasIncColumn() ? rs.getLong("MAX") : 0;
                var min = tableInfo.hasIncColumn() ? rs.getLong("MIN") : 0;
                var endTime = tableInfo.hasTimeColumns() ? taskRange.getExclusiveEndTime() : null;
                return CompletableFuture.completedFuture(new TaskInformation<>(taskRange,
                        new JDBCTaskMetadata(min, max + 1, previous.getEndTime(), endTime)));
            } else {
                return CompletableFuture.completedFuture(new TaskInformation<>(taskRange,
                        new JDBCTaskMetadata(startFrom, startFrom, previous.getEndTime(), previous.getEndTime())));
            }
        } catch (Exception e) {
            throw new RuntimeException("Failed to get task infos", e);
        }
    }

    private NamedPreparedStatment getTaskInfoQuery(JDBCTaskMetadata metadata,
                                                   TaskRange taskRange,
                                                   Connection connection) throws SQLException {
        if (tableInfo.hasTimeColumns()) {
            Instant maxTime = toQueryTime(taskRange.getExclusiveEndTime());
            if (tableInfo.getIncColumn() != null) {
                return queryDialect.taskInfoByIncAndTime(tableInfo, metadata, maxTime, connection);
            } else {
                return queryDialect.taskInfoByTime(tableInfo, metadata, maxTime, connection);
            }
        } else {
            return queryDialect.taskInfoByInc(tableInfo, metadata, connection);
        }
    }

    @Override
    public JDBCTaskMetadata reshard(List<JDBCTaskMetadata> previousTaskMetadatas,
                                    Instant taskTime,
                                    ShardDefinition newShard) {
        var endValue = previousTaskMetadatas.stream().mapToLong(JDBCTaskMetadata::getExclusiveEnd).max().orElse(-1L);
        var endTime = previousTaskMetadatas.stream().map(JDBCTaskMetadata::getEndTime)
                .max(Comparator.naturalOrder()).orElse(null);
        return new JDBCTaskMetadata(endValue, endValue, endTime, endTime);
    }

    @Override
    public void close() throws Exception {
        if (ds != null) {
            ds.close();
        }
    }
}