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Flink1.17之前实现JdbcLookup谓词下推
需求背景
Flink在1.17版本之前，flink-connector-jdbc的LookupJoin是不支持on条件下推的，例如on device_id=‘1’，查询SQL中是不会包含device_id='1’的条件，相关issue：https://issues.apache.org/jira/browse/FLINK-32321，在1.19版本该问题已经解决。谓词不下推会导致每次查询的数据量变多，本篇文章主要介绍如何在1.17支持谓词下推
技术实现
在JdbcDynamicTableSource中是已经支持谓词下推到连接器端的，支持连接器的Lookup查询没有将谓词下推应用到SQL语句上，所以我们主要变动如下两个类：
- JdbcDynamicTableSource
- JdbcRowDataLookupFunction
修改JdbcDynamicTableSource
位置：org.apache.flink.connector.jdbc.table.JdbcDynamicTableSource
目的：在getLookupRuntimeProvider方法中将将谓词下推的查询条件以及参数传入到LookupFunction中。
修改内容：如下代码
@Overridepublic LookupRuntimeProvider getLookupRuntimeProvider(LookupContext context) {// JDBC only support non-nested look up keysString[] keyNames = new String[context.getKeys().length];for (int i = 0; i < keyNames.length; i++) {int[] innerKeyArr = context.getKeys()[i];Preconditions.checkArgument(innerKeyArr.length == 1, "JDBC only support non-nested look up keys");keyNames[i] = DataType.getFieldNames(physicalRowDataType).get(innerKeyArr[0]);}final RowType rowType = (RowType) physicalRowDataType.getLogicalType();JdbcRowDataLookupFunction lookupFunction =new JdbcRowDataLookupFunction(options,lookupMaxRetryTimes,DataType.getFieldNames(physicalRowDataType).toArray(new String[0]),DataType.getFieldDataTypes(physicalRowDataType).toArray(new DataType[0]),keyNames,rowType,// 将谓词下推的查询条件以及参数传入到LookupFunction中resolvedPredicates,pushdownParams);if (cache != null) {return PartialCachingLookupProvider.of(lookupFunction, cache);} else {return LookupFunctionProvider.of(lookupFunction);}}
修改JdbcRowDataLookupFunction
位置：org.apache.flink.connector.jdbc.table.JdbcRowDataLookupFunction
目的：接受下推的条件及参数，重新拼装SQL，并在执行的时候将参数传入
修改内容：
- 构造方法支持接受下推的条件及参数两个变量，拼接条件语句，并将条件中的’?‘参数占位符替换为’:predicate_1’以支持FieldNamedPreparedStatement
public JdbcRowDataLookupFunction(JdbcConnectorOptions options,int maxRetryTimes,String[] fieldNames,DataType[] fieldTypes,String[] keyNames,RowType rowType,List<String> resolvedPredicates,Object[] pushdownParams) {checkNotNull(options, "No JdbcOptions supplied.");checkNotNull(fieldNames, "No fieldNames supplied.");checkNotNull(fieldTypes, "No fieldTypes supplied.");checkNotNull(keyNames, "No keyNames supplied.");this.connectionProvider = new SimpleJdbcConnectionProvider(options);List<String> nameList = Arrays.asList(fieldNames);DataType[] keyTypes =Arrays.stream(keyNames).map(s -> {checkArgument(nameList.contains(s),"keyName %s can't find in fieldNames %s.",s,nameList);return fieldTypes[nameList.indexOf(s)];}).toArray(DataType[]::new);this.maxRetryTimes = maxRetryTimes;// 添加谓词条件查询的逻辑List<String> predicateNames = new ArrayList<>(resolvedPredicates.size());List<String> fieldNamedPredicates = new ArrayList<>(resolvedPredicates.size());for (String pred : resolvedPredicates) {while (pred.contains("?")){String predicateName = "predicate_"+predicateNames.size();pred = pred.replaceFirst("\\?", ":" + predicateName);predicateNames.add(predicateName);}fieldNamedPredicates.add(String.format("(%s)", pred));}String joinedConditions = fieldNamedPredicates.isEmpty() ? "" : " AND " + String.join(" AND ", fieldNamedPredicates);this.pushdownParams = pushdownParams;this.conditionNames = ArrayUtils.concat(keyNames, predicateNames.toArray(new String[0]));this.query =options.getDialect().getSelectFromStatement(options.getTableName(), fieldNames, keyNames) + joinedConditions;LOG.debug("Query generated for JDBC lookup: " + query);JdbcDialect jdbcDialect = options.getDialect();this.jdbcRowConverter = jdbcDialect.getRowConverter(rowType);this.lookupKeyRowConverter =jdbcDialect.getRowConverter(RowType.of(Arrays.stream(keyTypes).map(DataType::getLogicalType).toArray(LogicalType[]::new)));}
- 修改establishConnectionAndStatement方法，在创建Statement是将新生成的conditionNames作为fieldNames传入
private void establishConnectionAndStatement() throws SQLException, ClassNotFoundException {Connection dbConn = connectionProvider.getOrEstablishConnection();statement = FieldNamedPreparedStatement.prepareStatement(dbConn, query, conditionNames);}
- 新增paddingPredicates方法用来想Statement中填充参数
private FieldNamedPreparedStatement paddingPredicates() throws SQLException {// 进行谓词填充int pushdowParamStartIndex = conditionNames.length - pushdownParams.length;for (int i = pushdowParamStartIndex; i < conditionNames.length; i++) {Object param = pushdownParams[i - pushdowParamStartIndex];if (param instanceof String) {statement.setString(i, (String) param);} else if (param instanceof Long) {statement.setLong(i, (Long) param);} else if (param instanceof Integer) {statement.setInt(i, (Integer) param);} else if (param instanceof Double) {statement.setDouble(i, (Double) param);} else if (param instanceof Boolean) {statement.setBoolean(i, (Boolean) param);} else if (param instanceof Float) {statement.setFloat(i, (Float) param);} else if (param instanceof BigDecimal) {statement.setBigDecimal(i, (BigDecimal) param);} else if (param instanceof Byte) {statement.setByte(i, (Byte) param);} else if (param instanceof Short) {statement.setShort(i, (Short) param);} else if (param instanceof Date) {statement.setDate(i, (Date) param);} else if (param instanceof Time) {statement.setTime(i, (Time) param);} else if (param instanceof Timestamp) {statement.setTimestamp(i, (Timestamp) param);} else {// extends with other types if neededthrow new IllegalArgumentException("Padding predicate failed. Parameter "+ i+ " of type "+ param.getClass()+ " is not handled (yet).");}}return statement;}
- 修改lookup方法，在执行查询之前，进行参数填充
/*** This is a lookup method which is called by Flink framework in runtime.** @param keyRow lookup keys*/@Overridepublic Collection<RowData> lookup(RowData keyRow) {for (int retry = 0; retry <= maxRetryTimes; retry++) {try {statement.clearParameters();// 谓词填充statement = paddingPredicates();statement = lookupKeyRowConverter.toExternal(keyRow, statement);try (ResultSet resultSet = statement.executeQuery()) {ArrayList<RowData> rows = new ArrayList<>();while (resultSet.next()) {RowData row = jdbcRowConverter.toInternal(resultSet);rows.add(row);}rows.trimToSize();return rows;}} catch (SQLException e) {LOG.error(String.format("JDBC executeBatch error, retry times = %d", retry), e);if (retry >= maxRetryTimes) {throw new RuntimeException("Execution of JDBC statement failed.", e);}try {if (!connectionProvider.isConnectionValid()) {statement.close();connectionProvider.closeConnection();establishConnectionAndStatement();}} catch (SQLException | ClassNotFoundException exception) {LOG.error("JDBC connection is not valid, and reestablish connection failed",exception);throw new RuntimeException("Reestablish JDBC connection failed", exception);}try {Thread.sleep(1000L * retry);} catch (InterruptedException e1) {throw new RuntimeException(e1);}}}return Collections.emptyList();}
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