Clickhouse show tables

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• one by default. The table contains a row for every Replicated * table. I am facing a problem in which Clickhouse frequently turns into read-only mode. 适用于高负载任务的最通用和功能最强大的表引擎。. 002 sec. If the port is omitted, it uses tcp_port from the server config file for table function remote (by default, 9000) and tcp_port_secure for table function remoteSecure (by default, 9440). So, you have to enable this feature with the command below. 如果没有表引擎声明，则创建的表将与 db2 It includes three nodes: two combined ClickHouse plus coordination (ClickHouse Keeper) servers, and a third server with only ClickHouse Keeper to finish the quorum of three. By default, SQL-driven access control and account management is disabled for all users. replica_num ( UInt32) — The replica number 9951 explained code solutions for 126 technologies. database ( String) – Alias for name. If a setting with the specified name does not exist, then the query raises an exception. ) The following table named is my_first_table in the helloworld database: user_id UInt32, message String, An overview of tables contained in your ClickHouse instance can be found in the left sidebar area. Sep 1, 2021 · We recommend having a maximum of 1000 databases and 5000 tables, 50000 partitions, and 100000 parts across all databases for a service. This section contains descriptions of server settings that cannot be changed at the session or query level. 例如： RegionID UInt32 。. ]name2 [ENGINE = engine] 创建一个与 db2. Gives the real-time access to table list and table structure from remote PostgreSQL with the help of SHOW TABLES and DESCRIBE TABLE queries. Codespaces. 54310. GROUP BY partition; if you just need to have another copy of data (for example with another key), you can just fill it with Materialized view automatically. Add a FORMAT clause to specify one of the many supported output formats of ClickHouse: SELECT *. PRIMARY KEY (user_id, message); The resulting table has three columns: And the primary key is (user_id, message). expr ( String) — Expression for the index calculation. It contains information about parts of MergeTree tables. Turns a subquery into a table. Like any other table, we can run typical select queries e. table — Remote table name. As example: Load 7 more related questions Show fewer related questions settings. Adding a materialized column. Allows to connect to databases on a remote PostgreSQL server. When the MATERIALIZED VIEW joins the engine, it starts collecting data in the background ALTER. table ( String) — Table name. Syntax. In the Databases and tables view, go to the table and select Actions > Remove > Delete table. gz'. Deduplication is implemented in ClickHouse using the following table engines: ReplacingMergeTree table engine: with this table engine, duplicate rows with the same sorting key are removed during merges. 此表包含以下列 (列类型显示在括号中): database ( String clickhouse get tables size . Create a materialized view that converts data from the engine and puts it into a previously created table. free_space ( UInt64) — Free space on disk in bytes. parquet'. Columns: name — Setting name. FROM helloworld. In the following procedures, the PostgreSQL CLI (psql) and the ClickHouse CLI (clickhouse-client) are used. Write better code with AI. System tables don't have files with data on the disk or files with metadata. Insert operations create table parts which are merged by engine_full ( String) — Parameters of the database engine. shard_num ( UInt32) — The shard number in the cluster, starting from 1. In this article, we will explain two system tables and give examples. SHOW TABLESctrl + c EXCHANGE TABLES. SELECT * FROM some_table SETTINGS optimize_read_in_order=1, cast_keep_nullable=1; Edit this page. SELECT queries perform data retrieval. The PostgreSQL server is installed on linux. Go to the table to remove: organization > project > service > Databases and tables. This example demonstrates how to create a events table in ClickHouse: user_id UInt32, timestamp DateTime, message String. 54235. This table can be used for monitoring. SummingMergeTree uses table's ORDER BY as a collapsing rule and the existing ORDER BY usually does not suit. set allow_experimental_undrop_table_query = 1; To change database_atomic_delay_before_drop_table_sec parameter, you can add a new config file into clickhouse-server config. The name column from this system table is used for implementing the SHOW DATABASES query. SHOW PROCESSLIST [INTO OUTFILE filename] [FORMAT format] Выводит содержимое таблицы system. With this example, we'll create a database, table, and a distributed table that will be able to query the data on both of the nodes. Possible values: 0 — Read, Write, and Change settings queries are allowed. For instance, instead of this non-atomic operation: INFORMATIONSCHEMA (or: informationschema) is a system database which provides a (somewhat) standardized, DBMS-agnostic view on metadata of database objects. Jan 26, 2023 · ClickHouse doesn't have a proper optimizer, so the right tables of the join require to be filtered before performing a join. 12. xml file on the ClickHouse server. Packages. Every query should be executed by calling one of the client’s execute methods: execute, execute_with_progress, execute_iter method. 该类型的引擎 Table Settings Manipulations. If ClickHouse can not determine the format from the file extension, then the output format defaults to TabSeparated for output data. Particularly it compares actual file sizes with the expected values which are stored on the server. У пользователя есть привилегия show, если Feb 20, 2021 · 如果未使用 FROM 字句，该查询返回当前数据库的所有表清单. Дополнительно. CLEAR INDEX IN PARTITION — Resets the specified secondary index in a partition. Find and fix vulnerabilities. Security. Supports read and write operations ( SELECT and INSERT queries) to exchange data between ClickHouse and PostgreSQL. The following has minimum settings if the postgresql database is new test install. . host:port — MySQL server address. 01 seconds) Or local table is 2X slower! My question. Instead of --host, --port, --user and --password options, ClickHouse client also supports connection strings (see next section). asked Mar 9, 2022 at 11:45. id ( UUID) — Role ID. (custom partitioning) Nov 5, 2017 · clickhouse-client -u readonly -h XXX; ClickHouse client version 1. A single query can change several settings at once. Read and write queries: INSERT. The schema of this table must align with the Debezium messages shown earlier. Other ways to make settings see here. storage ( String) — Path to the storage of roles. Aug 9, 2018 · I see that clickhouse created multiple directories for each partition key(in each node). The relevant data types will be chosen. CREATE MATERIALIZED VIEW str2dst TO dest_table AS SELECT * FROM source_table; Jun 15, 2023 · Readers familiar with ClickHouse will notice that this view inserts rows into our uk_price_paid and selects rows from a uk_price_paid_changes table. OPTIMIZE is a slow process, how can I monitor this process? clickhouse. path ( String) — Path to the mount point in the file system. Several entities can be renamed in a single query. ]name_2, ] [ON CLUSTER cluster] [SYNC] Limitations: If the clause IF EMPTY is specified, the server checks the emptiness of the table only on the replica which May 16, 2023 · In this blog post, we explore how hash tables are used in ClickHouse. Before studying the settings, read the Configuration files section and note the use of substitutions Dec 8, 2019 · ClickHouse allocate around 1-2Mb per column when you try insert any rows, so right answer is yes, it has not strict limit but limited by your CPU, Memory, concurrent client connections with insert and for *MergeTree table engines also restricted by number of partitions (see PARTITION BY in docs) edited Dec 9, 2019 at 13:03. ReplacingMergeTree is a good option for emulating upsert behavior (where you want queries to return the last row inserted). /clickhouse client. :) show create table system. Exchanges the names of two tables. Connecting to localhost:9000. tables WHERE database = <db> [AND name LIKE <pattern>] [LIMIT <N>] [INTO OUTFILE <filename>] [FORMAT <format>] 示例. First, this is an experimental feature of ClickHouse (v23. Available only for reading data. Instant dev environments. 下列查询获取最前面的2个位于 system 库中且 Mar 22, 2023 · INTO OUTFILE 'taxi_rides. ReplacingMergeTree, AggregatingMergeTree ) are the most commonly used and most robust table engines in ClickHouse. MergeTree. WHERE table = 'wikistat_top_projects'. Whether multithread request execution is possible. To remove your table in Aiven Console: Log in to the Aiven Console. 3: Start the client. System tables provide information about: Server states, processes, and environment. It's possible to change an Engine by several ways. rows, formatReadableSize(total_bytes) AS total_bytes_on_disk. Dec 21, 2022 · The complete list of system tables is accessible via the SHOW TABLES FROM system statement. ORDER BY timestamp. Feb 2, 2021 · Hi all Following is my Clickhouse details clickhouse-server: 20. Aliases \l - SHOW DATABASES \d - SHOW TABLES \c <DATABASE> - USE DATABASE. Here is an example of one the ways Feb 1, 2023 · must never called, when INVALIDATE_QUERY is set. Example. The keys in a named collection must match the parameter names of the corresponding function, table engine, database, etc. clickhouse-local. ; value — Setting value. table — 表名。类型: String。 user — 用户名。如果未指定用户，则使用 default 。类型: String。 password — 用户密码。如果未指定密码，则使用空密码。类型: String。 sharding_key — 分片键以支持在节点之间分布数据。 RENAME Statement. And the following file will be a compressed, tab-separated file: SELECT *. my_first_table. 99999% cases it does not make any sense. tables 显示。. So in 99. ]table_name AS [db2. ]table_A AND [db1. How to List Tables from a Database in ClickHouse. They are shown with the empty database field. Concurrent data access. Usually it's the table when the table was dropped plus database_atomic_delay_before_drop_table_sec. Options used when the ClickHouse binary was built. edited Feb 11, 2023 at 13:10. 1. But to look for tables on cluster, we have to add hostname field to differentiate hosts. 3). , to get its size on disk, we can do the following: SELECT. You should see a smiling face as it connects to your service running on localhost: my-host :) Jan 31, 2022 · Want to create tables based on the below requirement Hot Network Questions Proof/Reference to a claim about AC and definable real numbers table_dropped_time ( DateTime) — The time when the next attempt to remove table's data is scheduled on. Contains information about session settings for current user. ClickHouse client version 1. host_names_like (Array) — Names of hosts that are allowed to connect to the ClickHouse server, set using the LIKE predicate. Разрешает выполнять запросы show create table, describe. Type: String. When reading from the table, ClickHouse executes the query and deletes all This code will show all tables from 'default' database. To undo the deletion of a table, please see UNDROP TABLE. Instead they schedule ClickHouse Mutation that is executed independently (async) on background. Уровень: dictionary. Create a database. ClickHouse supports special functions for working with dictionaries that can be used in queries. Mar 9, 2022 · 1. SELECT * FROM system. 0 rows in set. Requires running OPTIMIZE on table. db Jun 12, 2022 · That means using Distributed table is = 2X faster (39:12. But it's impossible to change PARTITION BY / ORDER BY. host_names_regexp (Array) — Regular expression for host names that are allowed to connect to the ClickHouse server. EXCHANGE TABLES [db0. tables 中才可见。. 但是也可以为列另外定义默认值表达式（见后文）。. processes, которая содержит список запросов, выполняющихся в данный момент времени, кроме самих запросов SHOW PROCESSLIST. You can modify settings or reset them to default values. Creates a ClickHouse database with all the tables existing in MySQL, and all the data in those tables. To specify the output format, use the FORMAT clause. Oct 8, 2022 · Description connect clickhouse show tables error, comment not exists Code: 47, e. databases, to retrieve rows from a specified table. There are two conceptual types of queries: Read only queries: SELECT, SHOW, etc. show dictionaries. Contains information about existing data skipping indices in all the tables. Initially, we focus on the most common use case: using the Kafka table engine to insert data into ClickHouse from Kafka. columns table contains the following columns (the column type is shown in brackets): database ( String) — Database name. Columns: cluster ( String) — The cluster name. ALTER TABLE [db]. INTO OUTFILE 'taxi_rides. (If you do not specify the database name, the table will be in the default database. Example: SELECT *. This database engine is experimental. ┌──rows─┬─total_bytes_on_disk─┐. WHERE database = '' and table = 'source_table' and active = 1. Deletes one or more tables. Can’t be dropped or altered, but can be detached. Introduction. Create and work with databases and tables in Aiven for ClickHouse®. SELECT name FROM system. MergeTree系列引擎支持数据复制（使用 Replicated * 的引擎版本），分区和一些其他引擎不支持的其他功能。. 54318. Connecting to XXXX as user readonly. ClickHouse supports: Dictionaries with a set of functions. 临时表 只在创建它们的会话中的 system. ClickHouse stores access entity configurations in the folder set in the access_control_path server configuration parameter. ; changed — Shows whether a setting is changed from its default value. Table will be actually removed when it's not in use. SELECT * FROM events LIMIT 3. password — User password. replicas. name2 具有相同结构的表，同时你可以对其指定不同的表引擎声明。. Use the CREATE DATABASE command to create a new database in ClickHouse: Similarly, use CREATE TABLE to define a new table. Other settings are described in the “ Settings ” section. - repeat the last query; Shortkeys From your ClickHouse Cloud services list, choose the service that you will work with and click Connect. The views in INFORMATIONSCHEMA are generally inferior to normal system tables but tools can use them to obtain basic information in a cross-DBMS manner. Server’s internal processes. You can also find an expanded description for most system tables in our documentation. Keep in mind that, contrary to many how primary keys work in many other database systems, primary key values This article is to illustrate basic methods of integration using one database, one schema and one table. They simplify the creation of objects and the hiding of credentials from users without administrative access. You have to create a special Join engine table for the update. clickhouseList all tables from database. The table engine (type of table) determines: How and where data is stored, where to write it to, and where to read it from. user — MySQL user. ClickHouse recommend using built-in table functions in ClickHouse which provide a better alternative for ad-hoc querying scenarios (Postgres, MySQL, MongoDB, etc). Configured in the access_control_path parameter. 4 revision 54442 Number of replicas: 2 Number of shards : 2. Open a new Terminal, change directories to where your clickhouse binary is saved, and run the following command: . For MergeTree tables, consider using the DELETE FROM query, which performs a lightweight delete and can be considerably faster. That means that you can use join of the Distributed table with local tables to achieve expected result: SELECT xxx. FROM nyc_taxi. Whilst useful for viewing messages on a topic, the engine by design only permits one-time retrieval, i. Use the engine to create a table for consuming from specified path in S3 and consider it a data stream. Got exception on simple SHOW TABLES request: # clickhouse-client. Contains information and status for replicated tables residing on the local server. ALTER LIVE VIEW — Refreshes a Live view. EXCHANGE TABLES/DICTIONARIES EXCHANGE query swaps tables or dictionaries atomically. FREEZE PARTITION — Creates a backup of a partition. SELECT <expr_list>. The function implements views (see CREATE VIEW). tsv. Sep 14, 2023 · ClickHouse has a different data type structure. databases; MOVE PARTITION TO TABLE — Moves the data partition from one table to another. In the above query, the output is returned as tab-separated: Query id: 3604df1c-acfd-4117-9c56-f86c69721121. For example, below, I am sharing the table structure from MySQL and ClickHouse. FORMAT TabSeparated. Embedded dictionaries with a specific set of functions. However, the number of tables would affect the service startup time, so we recommend limiting the number of tables or partitions. Because if developers find a solution when we can set both QUERY and TABLE, we get two different methods to get data modification time executed when ClickHouse starts and when dictionary invalidate itself by timer Mar 21, 2022 · 4 rows in set. To do that, please follow the steps given below. Fortunately, there is a workaround. The query deletes rows in the table for which this MergeTree. These ALTER statements manipulate views: ALTER TABLE MODIFY QUERY — Modifies a Materialized view structure. 1. Most ALTER TABLE queries modify table settings or data: Most ALTER TABLE queries are supported only for * MergeTree tables, as well as Merge and Distributed. We show the schema of this table below: Aug 9, 2021 · 19. Renames databases, tables, or dictionaries. Databases in ClickHouse are more of a namespace and have no performance impact; 1000 databases is a loose guideline. E. total_space ( UInt64) — Disk volume in bytes. default_roles_all — Shows that all granted roles set for user by default. That's why it's not documented explicitly. Dec 11, 2017 · fsitedev commented on Dec 11, 2017. Contains information about clusters available in the config file and the servers in them. 分离的 表不在 system. Data replication parameters. CREATE TABLE [IF NOT EXISTS] [db. FORMAT Vertical. CREATE DATABASE test; Check all of the available databases to the user. clickhouse-local模式可以使您能够对本地文件执行快速处理，而无需部署和配置ClickHouse服务器。 接受表示表格tables的数据，并使用ClickHouse SQL方言查询它们。 clickhouse-local使用与ClickHouse Server相同的核心，因此它支持大多数功能以及相同的格式和表引擎。 Mar 14, 2019 · SELECT partition. We'll show how zero-cost abstractions work in modern C++ and how to get a variety of data structures from a common codebase with a few little tricks. system. GitHub Gist: instantly share code, notes, and snippets. milovidov-desktop :) CREATE TEMPORARY TABLE t (world UInt64) CREAT clusters. From here you can Open SQL console: If you are using self-managed ClickHouse you can connect to the SQL console at https:// hostname :8443/play (check with your ClickHouse administrator for the details). You can use the view function as a parameter of the remote and cluster table functions: See Also. type_full ( String) — Index type expression from create statement. Use it at your own risk. Nov 1, 2019 · SHOW TABLES ON CLUSTER is questionable, because it's expected that the query with ON CLUSTER modifier will return the dataset of the same structure as without ON CLUSTER. ]name_1[, [db2. The filter_expr must be of type UInt8. Use the database selector at the top of the left bar to view the tables in a specific database. How To Check Table and Column Sizes In ClickHouse. Why is it faster to load Distributed tables than local tables; How to quickly load data into local tables？(i 'am using --input_format_parallel_parsing=0 --compression=0,args There is no change in speed) thank you PostgreSQL. Use the clickhouse-client to connect to your ClickHouse service. Contains information about configured roles. name [ON CLUSTER cluster] MODIFY|RESET Re-insert the deleted row and force the TTL cleanup again with OPTIMIZE: INSERT INTO table_with_ttl VALUES (now() - INTERVAL 4 MONTH, 2, 'username2'); OPTIMIZE TABLE table_with_ttl FINAL; SELECT * FROM table_with_ttl FORMAT PrettyCompact; The TTL is no longer there, so the second row is not deleted: ┌─────────event_time ALTER TABLE is considered a heavyweight operation that requires the underlying data to be merged before it is deleted. First, system. For IPv6 addresses, a port is required. database — Remote database name. d file. To implement the JDBC connection, ClickHouse uses the separate program clickhouse-jdbc-bridge MaterializedMySQL. Запрос SELECT * FROM Table Engines. e. tables; SHOW CREATE TABLE system. Named collections can be configured with DDL or in configuration files and are applied when ClickHouse starts. Columns: name ( String) — Name of a disk in the server configuration. This latter table will receive row inserts from our Kafka sink. Connected to ClickHouse server version 1. 这些引擎的共同特点是可以快速插入数据并进行后续的后台数据处理。. Which queries are supported, and how. Jun 19, 2024 · DROP: Deleting a Table; SHOW: Displaying Information About Databases and Tables; User Management and Authentication; ClickHouse Multi-Tenancy; ClickHouse Table Engine Overview; Creating a ClickHouse Table; Migrating ClickHouse Data; Monitoring of Slow ClickHouse Query Statements and Replication Table Data Synchronization; Adaptive MV Usage in Queries like EXISTS, DESCRIBE, EXPLAIN, SHOW PROCESSLIST, etc are equivalent to SELECT, because they just do select from system tables. FROM system. 008 sec. The resulting table does not store data, but only stores the specified SELECT query. Use of indexes, if present. ClickHouse Joining Tables in ClickHouse. parts. It ensures the integrity of the data by verifying the checksums and other internal data structures. Columns: name ( String) — Role name. Elapsed: 0. You can run the following command to show all the tables in an existing database: SHOW TABLES FROM db_how_to; Edit this page on GitHub. The structure and content of views in INFORMATIONSCHEMA is supposed to evolves in a Aug 24, 2020 · Use case milovidov-desktop :) CREATE TABLE t (hello String) ENGINE = StripeLog CREATE TABLE t ( `hello` String ) ENGINE = StripeLog Ok. Setup a directory for configurations storage. Any idea what is level here? 347 distinct partition keys on one node(for one table) created 1358 directories. Allows ClickHouse to connect to external databases via JDBC. 可以用下面的方式获得和 SHOW TABLES 一样的结果：. Show hidden characters SELECT table, formatReadableSize(sum (bytes)) as size, Columns from temporary tables are visible in the system. The system. Create a table with the desired structure. ]table_B [ON CLUSTER cluster] Server JWT authorization is available only in ClickHouse Cloud. DROP TABLE. Automate any workflow. columns only in those session where they have been created. :) show tables. Nov 19, 2021 · I can assume that you are joining 3 Distributed tables: t1d, t2d, t3d. The following example shows how to get information about dropped_tables. Clickhouse will work as you expected: it will execute your request on each shard locally and then combine results at initiator. In this case DROP waits for running SELECT, INSERT and other queries which are using the table to finish. SHOW TABLES. With system tables, you can learn the details of the tables and columns on ClickHouse with the following queries. The MergeTree engine and other engines of the MergeTree family (e. System tables: Located in the system database. note. DB::Exception: Received from XXXX. CLEAR COLUMN IN PARTITION — Resets the value of a specified column in a partition. Host and manage packages. Using the example you've provided: WITH events_block AS (. replace_query — Flag that converts INSERT INTO queries to REPLACE INTO. g. The data types will be automatically converted by ClickHouse when we initiate the replication process. Разрешает выполнять запросы show dictionaries, show create dictionary, exists <dictionary>. It is easier and more efficient to use dictionaries with functions than a JOIN with reference tables. The Kafka table engine allows ClickHouse to read from a Kafka topic directly. Based on common building blocks, we can build a fast-cleaning hash table, several types of LRU caches, lookup tables without ClickHouse Connect passes the Arrow table unmodified to the ClickHouse server for processing, so only the database and settings arguments are available in addition to table and arrow_table. Joins are fully supported in ClickHouse with support for all standard SQL JOIN types. Query id: dc6dcbcb-dc28-4df9-ae27-4354f5b3b13e. Columns: database ( String) — Database name. parts table. It is a common operation in databases with SQL support, which corresponds to relational algebra join. when a query is issued to the table, it Jul 31, 2021 · I'm trying to drop a few tables at once on a ClickHouse cluster. You can compare the data types for the table we created. Version: 54318. If only parameter addresses_expr is specified, db and table will use system. The MySQL Table Engine is currently not available on the ClickHouse builds for MacOS ( issue) Engine Parameters. Syntax: DROP [TEMPORARY] TABLE [IF EXISTS] [IF EMPTY] [db1. These settings are stored in the config. type ( String) — Index type. WHERE table = 'test_table'. 2. There is a set of queries to change table settings. Another concern is that currently all ON CLUSTER queries are intended to perform some Sep 16, 2018 · Please note that all commands above do not execute the data mutation directly (in sync). Enable SQL-driven access control and account management for at least one user account. Level: Basic Terminology Replica roles. 29 seconds / 16:50. Contains information about disks defined in the server configuration. The setting value is applied only to this query and is reset to default or previous value after the query is executed. Otherwise, full tables will be pushed to memory to perform the join causing the issues you're experiencing. ALTER TABLE actions ADD COLUMN `total` UInt64 MATERIALIZED price1 + price2. GitHub Copilot. The special case of one table join is often referred to as “self-join”. shard_weight ( UInt32) — The relative weight of the shard when writing data. Contains information about tables that drop table has been Apr 20, 2019 · ClickHouse does not support dependent joins for ALTER TABLE UPDATE. You can't delete a system table (but you can perform DETACH). name ( String) — Index name. The syntax should look familiar, and you can view the docs page on JOIN for all the details: ClickHouse also provides additional non-standard SQL JOIN types useful for analytical workloads and for time-series analysis, including Join produces a new table by combining columns from one or multiple tables by using values common to each. tip. Note: A Numpy array is a valid Sequence of Sequences and can be used as the data argument to the main insert method, so a specialized method is not required. The server creates all the system tables when it starts. tables. Documentation says the directory name format is : partition ID_minimum block number_maximum block number_level. MergeTree -family table engines are designed for high data ingest rates and huge data volumes. The CHECK TABLE query in ClickHouse is used to perform a validation check on a specific table or its partitions. Tables in the list can also be expanded to view columns and types. Jan 19, 2023 · All metadata on materialized view tables is available in the system database like any other table. That is the reason why ALTER TABLE syntax was chosen instead of typical SQL UPDATE / DELETE. Note that the RENAME query with several entities is non-atomic operation. Exploring Table Data Click on a table in the list to open it in a new tab. displayText() = DB::Exception: Missing columns: 'comment' while processing query: 'SELECT name AS TABLE_NAME, engine AS TABLE_TYPE, database AS TABLE_SCHEM, System tables are used for implementing part of the system's functionality, and for providing access to information about how the system is working. To use it, set allow_experimental_database_materialized_mysql to 1 in your configuration files or by using the SET command: SET allow_experimental_database_materialized_mysql=1. 包含服务器知道的每个表的元数据。. OPTIMIZE TABLE actions FINAL. 它们的数据库字段显示为空，并且 is_temporary 标志显示为开启。. You can check unfinished Mutations' progress via. tables Received exception from server: Code: 107. bv sh xx kq to ix sc sj sh kf