The PRAGMA statement is a SQL extension adopted by DuckDB from SQLite. PRAGMA statements can be issued in a similar manner to regular SQL statements. PRAGMA commands may alter the internal state of the database engine, and can influence the subsequent execution or behavior of the engine.

PRAGMA statements that assign a value to an option can also be issued using the SET statement and the value of an option can be retrieved using SELECT current_setting(option_name).

For DuckDB's built in configuration options, see the Configuration Reference. DuckDB extensions may register additional configuration options. These are documented in the respective extensions' documentation pages.

This page contains the supported PRAGMA settings.

Metadata

Schema Information

List all databases:

PRAGMA database_list;

List all tables:

PRAGMA show_tables;

List all tables, with extra information, similarly to DESCRIBE:

PRAGMA show_tables_expanded;

To list all functions:

PRAGMA functions;

Table Information

Get info for a specific table:

PRAGMA table_info('table_name');
CALL pragma_table_info('table_name');

table_info returns information about the columns of the table with name table_name. The exact format of the table returned is given below:

cid INTEGER,        -- cid of the column
name VARCHAR,       -- name of the column
type VARCHAR,       -- type of the column
notnull BOOLEAN,    -- if the column is marked as NOT NULL
dflt_value VARCHAR, -- default value of the column, or NULL if not specified
pk BOOLEAN          -- part of the primary key or not

Database Size

Get the file and memory size of each database:

SET database_size;
CALL pragma_database_size();

database_size returns information about the file and memory size of each database. The column types of the returned results are given below:

database_name VARCHAR, -- database name
database_size VARCHAR, -- total block count times the block size
block_size BIGINT,     -- database block size
total_blocks BIGINT,   -- total blocks in the database
used_blocks BIGINT,    -- used blocks in the database
free_blocks BIGINT,    -- free blocks in the database
wal_size VARCHAR,      -- write ahead log size
memory_usage VARCHAR,  -- memory used by the database buffer manager
memory_limit VARCHAR   -- maximum memory allowed for the database

Storage Information

To get storage information:

PRAGMA storage_info('table_name');
CALL pragma_storage_info('table_name');

This call returns the following information for the given table:

See Storage for more information.

Show Databases

The following statement is equivalent to the SHOW DATABASES statement:

PRAGMA show_databases;

Resource Management

Memory Limit

Set the memory limit for the buffer manager:

SET memory_limit = '1GB';
SET max_memory = '1GB';

Warning The specified memory limit is only applied to the buffer manager. For most queries, the buffer manager handles the majority of the data processed. However, certain in-memory data structures such as vectors and query results are allocated outside of the buffer manager. Additionally, aggregate functions with complex state (e.g., list, mode, quantile, string_agg, and approx functions) use memory outside of the buffer manager. Therefore, the actual memory consumption can be higher than the specified memory limit.

Threads

Set the amount of threads for parallel query execution:

SET threads = 4;

Collations

List all available collations:

PRAGMA collations;

Set the default collation to one of the available ones:

SET default_collation = 'nocase';

Default Ordering for NULLs

Set the default ordering for NULLs to be either NULLS_FIRST, NULLS_LAST, NULLS_FIRST_ON_ASC_LAST_ON_DESC or NULLS_LAST_ON_ASC_FIRST_ON_DESC:

SET default_null_order = 'NULLS_FIRST';
SET default_null_order = 'NULLS_LAST_ON_ASC_FIRST_ON_DESC';

Set the default result set ordering direction to ASCENDING or DESCENDING:

SET default_order = 'ASCENDING';
SET default_order = 'DESCENDING';

Ordering by Non-Integer Literals

By default, ordering by non-integer literals is not allowed:

SELECT 42 ORDER BY 'hello world';

-- Binder Error: ORDER BY non-integer literal has no effect.

To allow this behavior, use the order_by_non_integer_literal option:

SET order_by_non_integer_literal = true;

Implicit Casting to VARCHAR

Prior to version 0.10.0, DuckDB would automatically allow any type to be implicitly cast to VARCHAR during function binding. As a result it was possible to e.g., compute the substring of an integer without using an explicit cast. For version v0.10.0 and later an explicit cast is needed instead. To revert to the old behavior that performs implicit casting, set the old_implicit_casting variable to true:

SET old_implicit_casting = true;

Python: Scan All Dataframes

Prior to version 1.1.0, DuckDB's replacement scan mechanism in Python scanned the global Python namespace. To revert to this old behavior, use the following setting:

SET python_scan_all_frames = true;

Information on DuckDB

Version

Show DuckDB version:

PRAGMA version;
CALL pragma_version();

Platform

platform returns an identifier for the platform the current DuckDB executable has been compiled for, e.g., osx_arm64. The format of this identifier matches the platform name as described in the extension loading explainer:

PRAGMA platform;
CALL pragma_platform();

User Agent

The following statement returns the user agent information, e.g., duckdb/v0.10.0(osx_arm64):

PRAGMA user_agent;

Metadata Information

The following statement returns information on the metadata store (block_id, total_blocks, free_blocks, and free_list):

PRAGMA metadata_info;

Progress Bar

Show progress bar when running queries:

PRAGMA enable_progress_bar;

Or:

PRAGMA enable_print_progress_bar;

Don't show a progress bar for running queries:

PRAGMA disable_progress_bar;

Or:

PRAGMA disable_print_progress_bar;

EXPLAIN Output

The output of EXPLAIN can be configured to show only the physical plan.

The default configuration of EXPLAIN:

SET explain_output = 'physical_only';

To only show the optimized query plan:

SET explain_output = 'optimized_only';

To show all query plans:

SET explain_output = 'all';

Profiling

Enable Profiling

The following query enables profiling with the default format, query_tree. Independent of the format, enable_profiling is mandatory to enable profiling.

PRAGMA enable_profiling;
PRAGMA enable_profile;

Profiling Format

The format of enable_profiling can be specified as query_tree, json, query_tree_optimizer, or no_output. Each format prints its output to the configured output, except no_output.

The default format is query_tree. It prints the physical query plan and the metrics of each operator in the tree.

SET enable_profiling = 'query_tree';

Alternatively, json returns the physical query plan as JSON:

SET enable_profiling = 'json';

To return the physical query plan, including optimizer and planner metrics:

SET enable_profiling = 'query_tree_optimizer';

Database drivers and other applications can also access profiling information through API calls, in which case users can disable any other output. Even though the parameter reads no_output, it is essential to note that this only affects printing to the configurable output. When accessing profiling information through API calls, it is still crucial to enable profiling:

SET enable_profiling = 'no_output';

Profiling Output

By default, DuckDB prints profiling information to the standard output. However, if you prefer to write the profiling information to a file, you can use PRAGMA profiling_output to specify a filepath.

Warning The file contents will be overwritten for every newly issued query. Hence, the file will only contain the profiling information of the last run query:

SET profiling_output = '/path/to/file.json';
SET profile_output = '/path/to/file.json';

Profiling Mode

By default, a limited amount of profiling information is provided (standard).

SET profiling_mode = 'standard';

For more details, use the detailed profiling mode by setting profiling_mode to detailed. The output of this mode includes profiling of the planner and optimizer stages.

SET profiling_mode = 'detailed';

Custom Metrics

By default, profiling enables all metrics except those activated by detailed profiling.

Using the custom_profiling_settings PRAGMA, each metric, including those from detailed profiling, can be individually enabled or disabled. This PRAGMA accepts a JSON object with metric names as keys and Boolean values to toggle them on or off. Settings specified by this PRAGMA override the default behavior.

Note This only affects the metrics when the enable_profiling is set to json or no_output. The query_tree and query_tree_optimizer always use a default set of metrics.

In the following example, the CPU_TIME metric is disabled. The EXTRA_INFO, OPERATOR_CARDINALITY, and OPERATOR_TIMING metrics are enabled.

SET custom_profiling_settings = '{"CPU_TIME": "false", "EXTRA_INFO": "true", "OPERATOR_CARDINALITY": "true", "OPERATOR_TIMING": "true"}';

The profiling documentation contains an overview of the available metrics.

Disable Profiling

To disable profiling:

PRAGMA disable_profiling;
PRAGMA disable_profile;

Query Optimization

Optimizer

To disable the query optimizer:

PRAGMA disable_optimizer;

To enable the query optimizer:

PRAGMA enable_optimizer;

Selectively Disabling Optimizers

The disabled_optimizers option allows selectively disabling optimization steps. For example, to disable filter_pushdown and statistics_propagation, run:

SET disabled_optimizers = 'filter_pushdown,statistics_propagation';

The available optimizations can be queried using the duckdb_optimizers() table function.

To re-enable the optimizers, run:

SET disabled_optimizers = '';

Warning The disabled_optimizers option should only be used for debugging performance issues and should be avoided in production.

Logging

Set a path for query logging:

SET log_query_path = '/tmp/duckdb_log/';

Disable query logging:

SET log_query_path = '';

Full-Text Search Indexes

The create_fts_index and drop_fts_index options are only available when the fts extension is loaded. Their usage is documented on the Full-Text Search extension page.

Verification

Verification of External Operators

Enable verification of external operators:

PRAGMA verify_external;

Disable verification of external operators:

PRAGMA disable_verify_external;

Verification of Round-Trip Capabilities

Enable verification of round-trip capabilities for supported logical plans:

PRAGMA verify_serializer;

Disable verification of round-trip capabilities:

PRAGMA disable_verify_serializer;

Object Cache

Enable caching of objects for e.g., Parquet metadata:

PRAGMA enable_object_cache;

Disable caching of objects:

PRAGMA disable_object_cache;

Checkpointing

Force Checkpoint

When CHECKPOINT is called when no changes are made, force a checkpoint regardless:

PRAGMA force_checkpoint;

Checkpoint on Shutdown

Run a CHECKPOINT on successful shutdown and delete the WAL, to leave only a single database file behind:

PRAGMA enable_checkpoint_on_shutdown;

Don't run a CHECKPOINT on shutdown:

PRAGMA disable_checkpoint_on_shutdown;

Temp Directory for Spilling Data to Disk

By default, DuckDB uses a temporary directory named ⟨database_file_name⟩.tmp to spill to disk, located in the same directory as the database file. To change this, use:

SET temp_directory = '/path/to/temp_dir.tmp/';

Returning Errors as JSON

The errors_as_json option can be set to obtain error information in raw JSON format. For certain errors, extra information or decomposed information is provided for easier machine processing. For example:

SET errors_as_json = true;

Then, running a query that results in an error produces a JSON output:

SELECT * FROM nonexistent_tbl;

{
   "exception_type":"Catalog",
   "exception_message":"Table with name nonexistent_tbl does not exist!\nDid you mean \"temp.information_schema.tables\"?",
   "name":"nonexistent_tbl",
   "candidates":"temp.information_schema.tables",
   "position":"14",
   "type":"Table",
   "error_subtype":"MISSING_ENTRY"
}

IEEE Floating-Point Operation Semantics

DuckDB follows IEEE floating-point operation semantics. If you would like to turn this off, run:

SET ieee_floating_point_ops = false;

In this case, floating point division by zero (e.g., 1.0 / 0.0, 0.0 / 0.0 and -1.0 / 0.0) will all return NULL.

Query Verification (for Development)

The following PRAGMAs are mostly used for development and internal testing.

Enable query verification:

PRAGMA enable_verification;

Disable query verification:

PRAGMA disable_verification;

Enable force parallel query processing:

PRAGMA verify_parallelism;

Disable force parallel query processing:

PRAGMA disable_verify_parallelism;

Block Sizes

When persisting a database to disk, DuckDB writes to a dedicated file containing a list of blocks holding the data. In the case of a file that only holds very little data, e.g., a small table, the default block size of 256KB might not be ideal. Therefore, DuckDB's storage format supports different block sizes.

There are a few constraints on possible block size values.

• Must be a power of two.
• Must be greater or equal to 16384 (16 KB).
• Must be lesser or equal to 262144 (256 KB).

You can set the default block size for all new DuckDB files created by an instance like so:

SET default_block_size = '16384';

It is also possible to set the block size on a per-file basis, see ATTACH for details.