max_query_size URL parameter stopped working

We use max_query_size as JDBC URL parameter to increase allowed select query size: jdbc:clickhouse://ch-host:8123/db?max_query_size=1000000

After switching from the deprecated package ru.yandex.clickhouse to the new one com.clickhouse.jdbc we discovered that this parameter is ignored and currently we have exceptions:

java.sql.BatchUpdateException: Code: 62. DB::Exception: Syntax error: failed at position 262144 ('86') (line 16, col 261384): 86. Max query size exceeded: '86'. (SYNTAX_ERROR) (version 21.12.3.32 (official build))
, server ClickHouseNode [uri=http://ch-host:8123/db, options={max_query_size=1000000,socket_timeout=30000,async=true,http_keep_alive=true}]@1448807023
	at com.clickhouse.jdbc.SqlExceptionUtils.batchUpdateError(SqlExceptionUtils.java:109)
	at com.clickhouse.jdbc.internal.SqlBasedPreparedStatement.executeAny(SqlBasedPreparedStatement.java:208)
	at com.clickhouse.jdbc.internal.SqlBasedPreparedStatement.executeQuery(SqlBasedPreparedStatement.java:235)

Position 262144 is related to the default limit of 256 KiB.

[zhicwu]

but I had to remove socket_timeout option and set it in url

socket_timeout is not a server setting so you have to put it separately in connection string or properties.

Am I right that all settings from ClickHouse Settings should be in custom_settings?

Yes, maybe it should be renamed to custom_server_settings but it’s getting too long to type in :p On a side note, if you have many settings to mange, you probably should consider to use server profile instead to benefit all type of clients instead of just JDBC.

Or could you please explain when to use custom_http_params, custom_settings and ordinary properties? And are there plans to support all params in url string?

custom_http_params only works when using http protocol and it should support arbitrary parameter regardless it’s a server setting or not. The driver will simply append the parameters to server url and then send http request accordingly. custom_settings on the other hand is more generic and it’s also supported by other protocols like grpc and tcp. I think in most cases we should use custom_settings, but if you’re using http and no plan to switch to any other protocol, you may use custom_http_params as well.

[zhicwu]

Hi @konstantinosss, you can add custom_http_params in connection property or url, for examples:

• connection property

  Properties props = new Properties();
  // comma separated custom settings, you can add custom_http_headers in a similar way as well
  props.setProperty("custom_http_params", "session_check=0,max_query_size=1000");
  

• connection url

  String url = "jdbc:clickhouse://ch-host:8123/db"
    // same as above but url encoded
    + "?custom_http_params=session_check%3D0%2Cmax_query_size%3D1000";
  

Sorry this is more of a workaround at this point because it’s limited to http protocol. I’ll add custom_settings to support more protocols.