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- List Functions 11273
- Function Description list[index] Extracts a single list element using a (1-based) index . list[begin[:end][:step]] Extracts a sublist using slice conventions . Negative values are accepted. list1 && list2 Alias for list_has_any . list1 <->
...If the sub-list in a list of lists only contains NULL , do not modify the sub-list: -- (Note the extra set of parentheses vs. the prior example) SELECT flatten([[NULL]]); [NULL] Even if the only contents of each sub-list is NULL , still concatenate... - https://man.mtool.work/duckdb/2.0/sql/functions/list.html
- Command Line Client 10362
- Installation To use the DuckDB CLI client, visit the CLI installation page . The latest stable version of the DuckDB command line client is 2.0.0. Installation The DuckDB CLI (Command Line Interface) is a single, dependency-free executable.
...in read-only mode (see concurrency in DuckDB ) For a full list of options, see the command line arguments page . In-Memory vs. Persistent Database When no ⟨FILENAME⟩ argument is provided, the DuckDB CLI will open a temporary in-memory database . You... - https://man.mtool.work/duckdb/2.0/clients/cli/overview.html
- WITH Clause 9820
- The WITH clause allows you to specify common table expressions (CTEs). Regular (non-recursive) common-table-expressions are essentially views that are limited in scope to a particular query. CTEs can reference each other and can be nested.
...th: UNION ALL forwards every candidate row to the next iteration, while UNION only forwards new or changed keys. See UNION vs. UNION ALL in USING KEY CTEs . The deprecated_using_key_syntax setting was removed. USING KEY alters the behavior of a regu...G KEY (a, max(b)) AS ( SELECT 1, 5, 'x' UNION ALL SELECT a, b - 1, 'y' FROM tbl WHERE b > 0 ) TABLE tbl; a b c 1 5 y UNION vs. UNION ALL in USING KEY CTEs Both UNION and UNION ALL update the union table in the same way: all rows produced by an itera... - https://man.mtool.work/duckdb/2.0/sql/query_syntax/with.html
- Versioning of Extensions 9365
- Extension Versioning Most software has some sort of version number. Version numbers serve a few important goals: Tie a binary to a specific state of the source code Allow determining the expected feature set Allow determining the state of t
...ion of DuckDB is released. However, note that DuckDB provides an extension template that makes this fairly simple. In-Tree vs. Out-of-Tree Originally, DuckDB extensions lived exclusively in the DuckDB main repository, github.com/duckdb/duckdb . Thes... - https://man.mtool.work/duckdb/2.0/extensions/versioning_of_extensions.html
- File Formats 9365
- Handling Parquet Files DuckDB has advanced support for Parquet files, which includes directly querying Parquet files . When deciding on whether to query these files directly or to first load them to the database, you need to consider severa
...e parquet_metadata function to find out the compression algorithm used. Microbenchmark: Running TPC-H on a DuckDB Database vs. Parquet The queries on the TPC-H benchmark run approximately 1.1-5.0× slower on Parquet files than on a DuckDB database. B... - https://man.mtool.work/duckdb/2.0/guides/performance/file_formats.html
- Environment 9260
- The environment where DuckDB is run has an obvious impact on performance. This page focuses on the effects of the hardware configuration and the operating system used. Hardware Configuration CPU DuckDB's officially supported architectures a
...and NVMe disks. While HDDs are supported, they will result in low performance, especially for write operations. Disk-based vs. in-memory storage. Counter-intuitively, using a disk-based DuckDB instance can be faster than an in-memory instance. This...buntu Linux LTS due to its stability and the fact that most of DuckDB's Linux test suite jobs run on Ubuntu workers. glibc vs. musl libc We distribute DuckDB builds with both glibc and musl libc . However, note that DuckDB binaries built with musl l... - https://man.mtool.work/duckdb/2.0/guides/performance/environment.html
- Tuning Workloads 9260
- DuckDB aims to perform well out of the box, so most workloads do not require any tuning. When tuning is worthwhile, there is no single configuration or magic number that is optimal for every workload: the right settings depend on what you a
...helpful if DuckDB is not CPU limited, but instead bottlenecked by another resource like network transfer speed. Persistent vs. In-Memory Tables DuckDB supports lightweight compression techniques . By default, compression is only applied on persisten... - https://man.mtool.work/duckdb/2.0/guides/performance/how_to_tune_workloads.html
- Securing DuckDB 9172
- DuckDB is a powerful analytical database engine. It can read and write files, access the network, load extensions, and use system resources. Like any powerful tool, these capabilities require appropriate configuration when working with sens
...loaded, you can disable autoloading: SET autoload_known_extensions = false; SET autoinstall_known_extensions = false; Core vs. Community Extensions DuckDB extensions fall into two categories: Core extensions: Maintained by the DuckDB team with full... - https://man.mtool.work/duckdb/2.0/operations_manual/securing_duckdb/overview.htm...
- CSV Auto Detection 8997
- When using read_csv , the system tries to automatically infer how to read the CSV file using the CSV sniffer . This step is necessary because CSV files are not self-describing and come in many different dialects. The auto-detection works ro
...his is set all columns will remain as VARCHAR (as they originally occur in the CSV file). Note that using quote characters vs. no quote characters (e.g., "42" and 42 ) does not make a difference for type detection. Quoted fields will not be converte... - https://man.mtool.work/duckdb/2.0/data/csv/auto_detection.html
- Indexing 8997
- DuckDB has two types of indexes: zonemaps and ART indexes. Zonemaps DuckDB automatically creates zonemaps (also known as min-max indexes) for the columns of all general-purpose data types . Operations like predicate pushdown into scan opera
...g For an example, let's repeat the microbenchmark for timestamps with an ordered timestamp column using an ascending order vs. an unordered one. Column type Ordered Storage size Query time DATETIME yes 1.3 GB 0.6 s DATETIME no 3.3 GB 0.9 s The resul... - https://man.mtool.work/duckdb/2.0/guides/performance/indexing.html
DuckDB 2.0 Documentation / man.mtool.work