DuckDB_% Metadata Functions

DuckDB offers a collection of table functions that provide metadata about the current database. These functions reside in the main schema and their names are prefixed with duckdb_.

The resultset returned by a duckdb_ table function may be used just like an ordinary table or view. For example, you can use a duckdb_ function call in the FROM clause of a SELECT statement, and you may refer to the columns of its returned resultset elsewhere in the statement, for example in the WHERE clause.

Table functions are still functions, and you should write parenthesis after the function name to call it to obtain its returned resultset:

SELECT * FROM duckdb_settings();

Alternatively, you may execute table functions also using the CALL-syntax:

CALL duckdb_settings();

In this case too, the parentheses are mandatory.

For some of the duckdb_% functions, there is also an identically named view available, which also resides in the main schema. Typically, these views do a SELECT on the duckdb_ table function with the same name, while filtering out those objects that are marked as internal. We mention it here, because if you accidentally omit the parentheses in your duckdb_ table function call, you might still get a result, but from the identically named view.

Example:

The duckdb_views() table function returns all views, including those marked internal:

SELECT * FROM duckdb_views();

The duckdb_views view returns views that are not marked as internal:

SELECT * FROM duckdb_views;

`duckdb_columns`

The duckdb_columns() function provides metadata about the columns available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains the column object.	`VARCHAR`
`database_oid`	Internal identifier of the database that contains the column object.	`BIGINT`
`schema_name`	The SQL name of the schema that contains the table object that defines this column.	`VARCHAR`
`schema_oid`	Internal identifier of the schema object that contains the table of the column.	`BIGINT`
`table_name`	The SQL name of the table that defines the column.	`VARCHAR`
`table_oid`	Internal identifier (name) of the table object that defines the column.	`BIGINT`
`column_name`	The SQL name of the column.	`VARCHAR`
`column_index`	The unique position of the column within its table.	`INTEGER`
`internal`	`true` if this column built-in, `false` if it is user-defined.	`BOOLEAN`
`column_default`	The default value of the column (expressed in SQL)	`VARCHAR`
`is_nullable`	`true` if the column can hold `NULL` values; `false` if the column cannot hold `NULL`-values.	`BOOLEAN`
`data_type`	The name of the column datatype.	`VARCHAR`
`data_type_id`	The internal identifier of the column data type.	`BIGINT`
`character_maximum_length`	Always `NULL`. DuckDB text types do not enforce a value length restriction based on a length type parameter.	`INTEGER`
`numeric_precision`	The number of units (in the base indicated by `numeric_precision_radix`) used for storing column values. For integral and approximate numeric types, this is the number of bits. For decimal types, this is the number of digits positions.	`INTEGER`
`numeric_precision_radix`	The number-base of the units in the `numeric_precision` column. For integral and approximate numeric types, this is `2`, indicating the precision is expressed as a number of bits. For the `decimal` type this is `10`, indicating the precision is expressed as a number of decimal positions.	`INTEGER`
`numeric_scale`	Applicable to `decimal` type. Indicates the maximum number of fractional digits (i.e., the number of digits that may appear after the decimal separator).	`INTEGER`

The information_schema.columns system view provides a more standardized way to obtain metadata about database columns, but the duckdb_columns function also returns metadata about DuckDB internal objects. (In fact, information_schema.columns is implemented as a query on top of duckdb_columns())

`duckdb_constraints`

The duckdb_constraints() function provides metadata about the constraints available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains the constraint.	`VARCHAR`
`database_oid`	Internal identifier of the database that contains the constraint.	`BIGINT`
`schema_name`	The SQL name of the schema that contains the table on which the constraint is defined.	`VARCHAR`
`schema_oid`	Internal identifier of the schema object that contains the table on which the constraint is defined.	`BIGINT`
`table_name`	The SQL name of the table on which the constraint is defined.	`VARCHAR`
`table_oid`	Internal identifier (name) of the table object on which the constraint is defined.	`BIGINT`
`constraint_index`	Indicates the position of the constraint as it appears in its table definition.	`BIGINT`
`constraint_type`	Indicates the type of constraint. Applicable values are `CHECK`, `FOREIGN KEY`, `PRIMARY KEY`, `NOT NULL`, `UNIQUE`.	`VARCHAR`
`constraint_text`	The definition of the constraint expressed as a SQL-phrase. (Not necessarily a complete or syntactically valid DDL-statement.)	`VARCHAR`
`expression`	If constraint is a check constraint, the definition of the condition being checked, otherwise `NULL`.	`VARCHAR`
`constraint_column_indexes`	An array of table column indexes referring to the columns that appear in the constraint definition.	`BIGINT[]`
`constraint_column_names`	An array of table column names appearing in the constraint definition.	`VARCHAR[]`

The information_schema.referential_constraints and information_schema.table_constraints system views provide a more standardized way to obtain metadata about constraints, but the duckdb_constraints function also returns metadata about DuckDB internal objects. (In fact, information_schema.referential_constraints and information_schema.table_constraints are implemented as a query on top of duckdb_constraints())

`duckdb_databases`

The duckdb_databases() function lists the databases that are accessible from within the current DuckDB process. Apart from the database associated at startup, the list also includes databases that were attached later on to the DuckDB process

Column	Description	Type
`database_name`	The name of the database, or the alias if the database was attached using an ALIAS-clause.	`VARCHAR`
`database_oid`	The internal identifier of the database.	`VARCHAR`
`path`	The file path associated with the database.	`VARCHAR`
`internal`	`true` indicates a system or built-in database. False indicates a user-defined database.	`BOOLEAN`
`type`	The type indicates the type of RDBMS implemented by the attached database. For DuckDB databases, that value is `duckdb`.	`VARCHAR`

`duckdb_dependencies`

The duckdb_dependencies() function provides metadata about the dependencies available in the DuckDB instance.

Column	Description	Type
`classid`	Always 0	`BIGINT`
`objid`	The internal id of the object.	`BIGINT`
`objsubid`	Always 0	`INTEGER`
`refclassid`	Always 0	`BIGINT`
`refobjid`	The internal id of the dependent object.	`BIGINT`
`refobjsubid`	Always 0	`INTEGER`
`deptype`	The type of dependency. Either regular (n) or automatic (a).	`VARCHAR`

`duckdb_extensions`

The duckdb_extensions() function provides metadata about the extensions available in the DuckDB instance.

Column	Description	Type
`extension_name`	The name of the extension.	`VARCHAR`
`loaded`	`true` if the extension is loaded, `false` if it's not loaded.	`BOOLEAN`
`installed`	`true` if the extension is installed, `false` if it's not installed.	`BOOLEAN`
`install_path`	`(BUILT-IN)` if the extension is built-in, otherwise, the filesystem path where binary that implements the extension resides.	`VARCHAR`
`description`	Human readable text that describes the extension's functionality.	`VARCHAR`
`aliases`	List of alternative names for this extension.	`VARCHAR[]`

`duckdb_functions`

The duckdb_functions() function provides metadata about the functions (including macros) available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains this function.	`VARCHAR`
`schema_name`	The SQL name of the schema where the function resides.	`VARCHAR`
`function_name`	The SQL name of the function.	`VARCHAR`
`function_type`	The function kind. Value is one of: `table`,`scalar`,`aggregate`,`pragma`,`macro`	`VARCHAR`
`description`	Description of this function (always `NULL`)	`VARCHAR`
`return_type`	The logical data type name of the returned value. Applicable for scalar and aggregate functions.	`VARCHAR`
`parameters`	If the function has parameters, the list of parameter names.	`VARCHAR[]`
`parameter_types`	If the function has parameters, a list of logical data type names corresponding to the parameter list.	`VARCHAR[]`
`varargs`	The name of the data type in case the function has a variable number of arguments, or `NULL` if the function does not have a variable number of arguments.	`VARCHAR`
`macro_definition`	If this is a macro, the SQL expression that defines it.	`VARCHAR`
`has_side_effects`	`false` if this is a pure function. `true` if this function changes the database state (like sequence functions `nextval()` and `curval()`).	`BOOLEAN`
`function_oid`	The internal identifier for this function	`BIGINT`

`duckdb_indexes`

The duckdb_indexes() function provides metadata about secondary indexes available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains this index.	`VARCHAR`
`database_oid`	Internal identifier of the database containing the index.	`BIGINT`
`schema_name`	The SQL name of the schema that contains the table with the secondary index.	`VARCHAR`
`schema_oid`	Internal identifier of the schema object.	`BIGINT`
`index_name`	The SQL name of this secondary index.	`VARCHAR`
`index_oid`	The object identifier of this index.	`BIGINT`
`table_name`	The name of the table with the index.	`VARCHAR`
`table_oid`	Internal identifier (name) of the table object.	`BIGINT`
`is_unique`	`true` if the index was created with the `UNIQUE` modifier, `false` if it was not.	`BOOLEAN`
`is_primary`	Always `false`	`BOOLEAN`
`expressions`	Always `NULL`	`VARCHAR`
`sql`	The definition of the index, expressed as a `CREATE INDEX` SQL statement.	`VARCHAR`

Note that duckdb_indexes only provides metadata about secondary indexes, i.e., those indexes created by explicit CREATE INDEX statements. Primary keys, foreign keys, and UNIQUE constraints are maintained using indexes, but their details are included in the duckdb_constraints() function.

`duckdb_keywords`

The duckdb_keywords() function provides metadata about DuckDB's keywords and reserved words.

Column	Description	Type
`keyword_name`	The keyword.	`VARCHAR`
`keyword_category`	Indicates the category of the keyword. Values are `column_name`, `reserved`, `type_function` and `unreserved`.	`VARCHAR`

`duckdb_memory`

The duckdb_memory() function provides metadata about DuckDB's buffer manager.

Column	Description	Type
`tag`	The memory tag. It has one of the following values: `BASE_TABLE`, `HASH_TABLE`, `PARQUET_READER`, `CSV_READER`, `ORDER_BY`, `ART_INDEX`, `COLUMN_DATA`, `METADATA`, `OVERFLOW_STRINGS`, `IN_MEMORY_TABLE`, `ALLOCATOR`, `EXTENSION`.	`VARCHAR`
`memory_usage_bytes`	The memory used (in bytes).	`BIGINT`
`temporary_storage_bytes`	The disk storage used (in bytes).	`BIGINT`

`duckdb_optimizers`

The duckdb_optimizers() function provides metadata about the optimization rules (e.g., expression_rewriter, filter_pushdown) available in the DuckDB instance. These can be selectively turned off using PRAGMA disabled_optimizers.

Column	Description	Type
`name`	The name of the optimization rule.	`VARCHAR`

`duckdb_schemas`

The duckdb_schemas() function provides metadata about the schemas available in the DuckDB instance.

Column	Description	Type
`oid`	Internal identifier of the schema object.	`BIGINT`
`database_name`	The name of the database that contains this schema.	`VARCHAR`
`database_oid`	Internal identifier of the database containing the schema.	`BIGINT`
`schema_name`	The SQL name of the schema.	`VARCHAR`
`internal`	`true` if this is an internal (built-in) schema, `false` if this is a user-defined schema.	`BOOLEAN`
`sql`	Always `NULL`	`VARCHAR`

The information_schema.schemata system view provides a more standardized way to obtain metadata about database schemas.

`duckdb_secrets`

The duckdb_secrets() function provides metadata about the secrets available in the DuckDB instance.

Column	Description	Type
`name`	The name of the secret.	`VARCHAR`
`type`	The type of the secret, e.g., `S3`, `GCS`, `R2`, `AZURE`.	`VARCHAR`
`provider`	The provider of the secret.	`VARCHAR`
`persistent`	Denotes whether the secret is persisent.	`BOOLEAN`
`storage`	The backend for storing the secret.	`VARCHAR`
`scope`	The scope of the secret.	`VARCHAR[]`
`secret_string`	Returns the content of the secret as a string. Sensitive pieces of information, e.g., they access key, are redacted.	`VARCHAR`

`duckdb_sequences`

The duckdb_sequences() function provides metadata about the sequences available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains this sequence	`VARCHAR`
`database_oid`	Internal identifier of the database containing the sequence.	`BIGINT`
`schema_name`	The SQL name of the schema that contains the sequence object.	`VARCHAR`
`schema_oid`	Internal identifier of the schema object that contains the sequence object.	`BIGINT`
`sequence_name`	The SQL name that identifies the sequence within the schema.	`VARCHAR`
`sequence_oid`	The internal identifier of this sequence object.	`BIGINT`
`temporary`	Whether this sequence is temporary. Temporary sequences are transient and only visible within the current connection.	`BOOLEAN`
`start_value`	The initial value of the sequence. This value will be returned when `nextval()` is called for the very first time on this sequence.	`BIGINT`
`min_value`	The minimum value of the sequence.	`BIGINT`
`max_value`	The maximum value of the sequence.	`BIGINT`
`increment_by`	The value that is added to the current value of the sequence to draw the next value from the sequence.	`BIGINT`
`cycle`	Whether the sequence should start over when drawing the next value would result in a value outside the range.	`BOOLEAN`
`last_value`	`null` if no value was ever drawn from the sequence using `nextval(...)`. `1` if a value was drawn.	`BIGINT`
`sql`	The definition of this object, expressed as SQL DDL-statement.	`VARCHAR`

Attributes like temporary, start_value etc. correspond to the various options available in the CREATE SEQUENCE statement and are documented there in full. Note that the attributes will always be filled out in the duckdb_sequences resultset, even if they were not explicitly specified in the CREATE SEQUENCE statement.

The column name last_value suggests that it contains the last value that was drawn from the sequence, but that is not the case. It's either null if a value was never drawn from the sequence, or 1 (when there was a value drawn, ever, from the sequence).

If the sequence cycles, then the sequence will start over from the boundary of its range, not necessarily from the value specified as start value.

`duckdb_settings`

The duckdb_settings() function provides metadata about the settings available in the DuckDB instance.

Column	Description	Type
`name`	Name of the setting.	`VARCHAR`
`value`	Current value of the setting.	`VARCHAR`
`description`	A description of the setting.	`VARCHAR`
`input_type`	The logical datatype of the setting's value.	`VARCHAR`

The various settings are described in the configuration page.

`duckdb_tables`

The duckdb_tables() function provides metadata about the base tables available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains this table	`VARCHAR`
`database_oid`	Internal identifier of the database containing the table.	`BIGINT`
`schema_name`	The SQL name of the schema that contains the base table.	`VARCHAR`
`schema_oid`	Internal identifier of the schema object that contains the base table.	`BIGINT`
`table_name`	The SQL name of the base table.	`VARCHAR`
`table_oid`	Internal identifier of the base table object.	`BIGINT`
`internal`	`false` if this is a user-defined table.	`BOOLEAN`
`temporary`	Whether this is a temporary table. Temporary tables are not persisted and only visible within the current connection.	`BOOLEAN`
`has_primary_key`	`true` if this table object defines a `PRIMARY KEY`.	`BOOLEAN`
`estimated_size`	The estimated number of rows in the table.	`BIGINT`
`column_count`	The number of columns defined by this object.	`BIGINT`
`index_count`	The number of indexes associated with this table. This number includes all secondary indexes, as well as internal indexes generated to maintain `PRIMARY KEY` and/or `UNIQUE` constraints.	`BIGINT`
`check_constraint_count`	The number of check constraints active on columns within the table.	`BIGINT`
`sql`	The definition of this object, expressed as SQL `CREATE TABLE`-statement.	`VARCHAR`

The information_schema.tables system view provides a more standardized way to obtain metadata about database tables that also includes views. But the resultset returned by duckdb_tables contains a few columns that are not included in information_schema.tables.

`duckdb_temporary_files`

The duckdb_temporary_files() function provides metadata about the temporary files DuckDB has written to disk, to offload data from memory. This function mostly exists for debugging and testing purposes.

Column	Description	Type
`path`	The name of the temporary file.	`VARCHAR`
`size`	The size in bytes of the temporary file.	`BIGINT`

`duckdb_types`

The duckdb_types() function provides metadata about the data types available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains this schema.	`VARCHAR`
`database_oid`	Internal identifier of the database that contains the data type.	`BIGINT`
`schema_name`	The SQL name of the schema containing the type definition. Always `main`.	`VARCHAR`
`schema_oid`	Internal identifier of the schema object.	`BIGINT`
`type_name`	The name or alias of this data type.	`VARCHAR`
`type_oid`	The internal identifier of the data type object. If `NULL`, then this is an alias of the type (as identified by the value in the `logical_type` column).	`BIGINT`
`type_size`	The number of bytes required to represent a value of this type in memory.	`BIGINT`
`logical_type`	The 'canonical' name of this data type. The same `logical_type` may be referenced by several types having different `type_name`s.	`VARCHAR`
`type_category`	The category to which this type belongs. Data types within the same category generally expose similar behavior when values of this type are used in expression. For example, the `NUMERIC` type_category includes integers, decimals, and floating point numbers.	`VARCHAR`
`internal`	Whether this is an internal (built-in) or a user object.	`BOOLEAN`

`duckdb_variables`

The duckdb_variables() function provides metadata about the variables available in the DuckDB instance.

Column	Description	Type
`name`	The name of the variable, e.g., `x`.	`VARCHAR`
`value`	The value of the variable, e.g. `12`.	`VARCHAR`
`type`	The type of the variable, e.g., `INTEGER`.	`VARCHAR`

`duckdb_views`

The duckdb_views() function provides metadata about the views available in the DuckDB instance.

Column	Description	Type
`database_name`	The name of the database that contains this view.	`VARCHAR`
`database_oid`	Internal identifier of the database that contains this view.	`BIGINT`
`schema_name`	The SQL name of the schema where the view resides.	`VARCHAR`
`schema_oid`	Internal identifier of the schema object that contains the view.	`BIGINT`
`view_name`	The SQL name of the view object.	`VARCHAR`
`view_oid`	The internal identifier of this view object.	`BIGINT`
`internal`	`true` if this is an internal (built-in) view, `false` if this is a user-defined view.	`BOOLEAN`
`temporary`	`true` if this is a temporary view. Temporary views are not persistent and are only visible within the current connection.	`BOOLEAN`
`column_count`	The number of columns defined by this view object.	`BIGINT`
`sql`	The definition of this object, expressed as SQL DDL-statement.	`VARCHAR`

The information_schema.tables system view provides a more standardized way to obtain metadata about database views that also includes base tables. But the resultset returned by duckdb_views contains also definitions of internal view objects as well as a few columns that are not included in information_schema.tables.