MartijnVisser commented on code in PR #171: URL: https://github.com/apache/flink-connector-jdbc/pull/171#discussion_r4417117559
########## flink-connector-jdbc-clickhouse/src/main/java/org/apache/flink/connector/jdbc/clickhouse/database/dialect/ClickHouseDialect.java: ########## @@ -0,0 +1,139 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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 org.apache.flink.connector.jdbc.clickhouse.database.dialect; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.connector.jdbc.core.database.dialect.AbstractDialect; +import org.apache.flink.connector.jdbc.core.database.dialect.JdbcDialectConverter; +import org.apache.flink.table.types.logical.LogicalTypeRoot; +import org.apache.flink.table.types.logical.RowType; + +import java.util.Arrays; +import java.util.EnumSet; +import java.util.Optional; +import java.util.Set; +import java.util.stream.Collectors; + +import static java.lang.String.format; + +/** JDBC dialect for ClickHouse. */ +@Internal +public class ClickHouseDialect extends AbstractDialect { + + private static final long serialVersionUID = 1L; + + // Define MAX/MIN precision of TIMESTAMP type according to ClickHouse docs: + // https://clickhouse.com/docs/sql-reference/data-types/datetime64 + private static final int MAX_TIMESTAMP_PRECISION = 9; + private static final int MIN_TIMESTAMP_PRECISION = 0; + + // Define MAX/MIN precision of DECIMAL type according to ClickHouse docs: + // https://clickhouse.com/docs/sql-reference/data-types/decimal + private static final int MAX_DECIMAL_PRECISION = 76; + private static final int MIN_DECIMAL_PRECISION = 1; + + @Override + public JdbcDialectConverter getRowConverter(RowType rowType) { + return new ClickHouseDialectConverter(rowType); + } + + @Override + public String getLimitClause(long limit) { + return "LIMIT " + limit; + } + + @Override + public Optional<String> defaultDriverName() { + return Optional.of("com.clickhouse.jdbc.Driver"); + } + + @Override + public String dialectName() { + return "ClickHouse"; + } + + @Override + public String quoteIdentifier(String identifier) { + return identifier; + } + + // ClickHouse does not support Upsert statements + // Instead you can create a table with ReplacingMergeTree engine; + // https://clickhouse.com/docs/engines/table-engines/mergetree-family/replacingmergetree + @Override + public Optional<String> getUpsertStatement( + String tableName, String[] fieldNames, String[] uniqueKeyFields) { + return Optional.empty(); Review Comment: Agreed, it gives no duplicates, I checked that with a failover. But pending mutations are not visible either unless readers set `apply_mutations_on_fly`, much like `FINAL`. The real problem is on the write side: ClickHouse rejects new mutations once 1000 are pending by default, so 3000 updates on a 20M-row table fail the job with `TOO_MANY_MUTATIONS`. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
