6.4 KiB
6.4 KiB
InfluxDB SQL Repl Tips and Tricks
InfluxDB IOx contains a built in SQL client you can use to interact with the server using SQL
Quick Start
influxdb_iox --host http://localhost:8082 sql
Connected to IOx Server at http://localhost:8082
Ready for commands. (Hint: try 'help;')
>
Remote Mode
In this mode queries are run on the remote server in the context of a database. To use this mode, specify a database and then run queries as normal
> show databases;
+-----------------------------------+
| db_name |
+-----------------------------------+
| 084d710ebdd819a5_apps |
| 7f4b06e9112d7bc8_system%255Fusage |
| 7f4b06e9112d7bc8_system%5Fusage |
| 844910ece80be8bc_057abada752bc8ce |
| 844910ece80be8bc_05a7a51565539000 |
+-----------------------------------+
Then run the USE DATABASE command
> use database my_db;
You are now in remote mode, querying database my_db
my_db>
Now, all queries will be run against the specified database (my_db) in this example
my_db> show tables;
+---------------+--------------------+-------------+------------+
| table_catalog | table_schema | table_name | table_type |
+---------------+--------------------+-------------+------------+
| public | iox | query_count | BASE TABLE |
| public | system | chunks | BASE TABLE |
| public | system | columns | BASE TABLE |
| public | system | operations | BASE TABLE |
| public | information_schema | tables | VIEW |
| public | information_schema | columns | VIEW |
+---------------+--------------------+-------------+------------+
Query execution complete in 32.034867ms
my_db> select count(*) from query_count;
+-----------------+
| COUNT(UInt8(1)) |
+-----------------+
| 2 |
+-----------------+
Query execution complete in 46.852934ms
Observer
In this mode queries are run locally against a cached unified view of the remote system tables
my_db> observer;
Preparing local views of remote system tables
Loading system tables from 49 databases
...................................................................................................................................................
Completed in 4.048318429s
You are now in Observer mode.
SQL commands in this mode run against a cached unified view of
remote system tables in all remote databases.
To see the unified tables available to you, try running
SHOW TABLES;
To reload the most recent version of the database system tables, run
OBSERVER;
Example SQL to show the total estimated storage size by database:
SELECT database_name, storage, count(*) as num_chunks,
sum(estimated_bytes)/1024/1024 as estimated_mb
FROM chunks
GROUP BY database_name, storage
ORDER BY estimated_mb desc;
OBSERVER>
Query Cookbook
This section contains some common and useful queries against IOx system tables
Explore Schema
The SHOW TABLES command will show all tables available to you.
my_db> show tables;
+---------------+--------------------+-------------+------------+
| table_catalog | table_schema | table_name | table_type |
+---------------+--------------------+-------------+------------+
| public | iox | query_count | BASE TABLE |
| public | system | chunks | BASE TABLE |
| public | system | columns | BASE TABLE |
| public | system | operations | BASE TABLE |
| public | information_schema | tables | VIEW |
| public | information_schema | columns | VIEW |
+---------------+--------------------+-------------+------------+
Query execution complete in 45.06072ms
tables in the iox schema are those that you have loaded (query_count) in this example. Tables which allow you to interrogate IOx's internals are in the system schema. The information_schema schema contains SQL standard views for accessing table and column metadata.
The SHOW COLUMNS FROM <tablename> command will show the columns in a table
my_db> show columns from query_count;
+---------------+--------------+-------------+-------------+-----------------------------+-------------+
| table_catalog | table_schema | table_name | column_name | data_type | is_nullable |
+---------------+--------------+-------------+-------------+-----------------------------+-------------+
| public | iox | query_count | avg | Int64 | YES |
| public | iox | query_count | time | Timestamp(Nanosecond, None) | NO |
+---------------+--------------+-------------+-------------+-----------------------------+-------------+
Query execution complete in 62.77733ms
A classic trick to explore a table's schema is to select from it with a limit. For example:
my_db> select * from query_count limit 2;
+-----+---------------------+
| avg | time |
+-----+---------------------+
| 461 | 2021-04-28 16:51:00 |
| 402 | 2021-04-28 17:51:00 |
+-----+---------------------+
Query execution complete in 39.046225ms
System Tables
Here are some interesting reports you can run when in OBSERVER mode:
Total storage size taken by each database
SELECT
database_name, count(*) as num_chunks,
sum(estimated_bytes)/1024/1024 as estimated_mb
FROM chunks
GROUP BY database_name
ORDER BY estimated_mb desc
LIMIT 20;
Total estimated storage size by database and storage class
SELECT
database_name, storage, count(*) as num_chunks,
sum(estimated_bytes)/1024/1024 as estimated_mb
FROM chunks
GROUP BY database_name, storage
ORDER BY estimated_mb desc
LIMIT 20;
Total estimated storage size by database, table_name and storage class
SELECT
database_name, table_name, storage, count(*) as num_chunks,
sum(estimated_bytes)/1024/1024 as estimated_mb
FROM chunks
GROUP BY database_name, table_name, storage
ORDER BY estimated_mb desc
LIMIT 20;
Total row count by table
SELECT database_name, table_name, max(count) as total_rows
FROM columns
GROUP BY database_name, table_name
ORDER BY total_rows DESC
LIMIT 20;
Total row count by partition and table
SELECT database_name, partition_key, table_name, max(count) as total_rows
FROM columns
GROUP BY database_name, partition_key, table_name
ORDER BY total_rows DESC
LIMIT 20;