How to list InfluxDB 3 Core table schema

Listing an InfluxDB 3 Core table schema shows which tables exist and which columns are tags, fields, or time. It is the check to run before writing SQL queries, building dashboard panels, or comparing a migrated database against the expected layout.

InfluxDB 3 Core exposes user data tables through the iox schema. The SHOW TABLES statement lists user tables alongside system and information-schema metadata, while SHOW COLUMNS reports the SQL data type for each column in a selected table.

Use the same database endpoint and token that applications use for reads. A token with read access is enough for schema inspection, and a table may appear only after an explicit table creation or a first write has established its columns.

1. Set the token for the schema check.

   $ export INFLUXDB3_AUTH_TOKEN='INFLUXDB_ADMIN_TOKEN'

   Use a token with read access to the target database. Keep raw tokens out of shared logs, screenshots, and shell history.

2. Set the host URL when the server is not on the default local listener.

   $ export INFLUXDB3_HOST_URL=http://localhost:8181

   Skip this when querying the default local listener at http://127.0.0.1:8181. Use the proxy or TLS URL that the client should actually test.

3. List tables in the database.

   $ influxdb3 query --database sensors "SHOW TABLES"
   +---------------+--------------------+-------------------------------------+------------+
   | table_catalog | table_schema       | table_name                          | table_type |
   +---------------+--------------------+-------------------------------------+------------+
   | public        | iox                | weather                             | BASE TABLE |
   | public        | system             | distinct_caches                     | BASE TABLE |
   | public        | system             | influxdb_schema                     | BASE TABLE |
   ##### snipped #####
   | public        | information_schema | columns                             | VIEW       |
   | public        | information_schema | df_settings                         | VIEW       |
   +---------------+--------------------+-------------------------------------+------------+

   Rows with table_schema set to iox are user tables. System and information-schema rows describe server metadata, query activity, and SQL catalog views.

4. List columns for the target table.

   $ influxdb3 query --database sensors "SHOW COLUMNS IN weather"
   +---------------+--------------+------------+-------------+-------------------------+-------------+
   | table_catalog | table_schema | table_name | column_name | data_type               | is_nullable |
   +---------------+--------------+------------+-------------+-------------------------+-------------+
   | public        | iox          | weather    | humidity    | Float64                 | YES         |
   | public        | iox          | weather    | room        | Dictionary(Int32, Utf8) | YES         |
   | public        | iox          | weather    | temperature | Float64                 | YES         |
   | public        | iox          | weather    | time        | Timestamp(ns)           | NO          |
   +---------------+--------------+------------+-------------+-------------------------+-------------+

   Dictionary(Int32, Utf8) identifies a tag-like string dictionary column in SQL output. Numeric fields appear as Float64, Int64, UInt64, or another field type.

5. Show tag and field roles from the InfluxDB schema table.

   $ influxdb3 show system --database sensors table influxdb_schema
   +-------------+-------------+-----------+
   | measurement | key         | data_type |
   +-------------+-------------+-----------+
   | weather     | humidity    | float     |
   | weather     | room        | tag       |
   | weather     | temperature | float     |
   | weather     | time        | time      |
   +-------------+-------------+-----------+

   influxdb_schema uses measurement for the table name and key for the column name. The data_type value distinguishes tags, fields, and the time column.
   Related: How to query InfluxDB 3 Core system data

6. Query information_schema.columns when another SQL client needs the same metadata.

   $ influxdb3 query --database sensors "SELECT column_name, data_type FROM information_schema.columns WHERE table_schema = 'iox' AND table_name = 'weather' ORDER BY ordinal_position"
   +-------------+-------------------------+
   | column_name | data_type               |
   +-------------+-------------------------+
   | humidity    | Float64                 |
   | room        | Dictionary(Int32, Utf8) |
   | temperature | Float64                 |
   | time        | Timestamp(ns)           |
   +-------------+-------------------------+

   Use the table_schema = 'iox' filter to avoid system and information-schema columns when the task is limited to user data tables.