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- Samples 13694
- Samples are used to randomly select a subset of a dataset. Examples Select a sample of exactly 5 rows from tbl using reservoir sampling: SELECT * FROM tbl USING SAMPLE 5; Select a sample of approximately 10% of the table using system sampli
...o rows at all. To get exactly 10% of rows (up to rounding), you must use the reservoir sampling option. Select a sample of approximately 10% of the table using bernoulli sampling: SELECT * FROM tbl USING SAMPLE 10 PERCENT (bernoulli); Select a sample of exact...r sampling with a fixed seed (100): SELECT * FROM tbl USING SAMPLE reservoir(50 ROWS) REPEATABLE (100); Select a sample of approximately 20% of the table using system sampling with a fixed seed (377): SELECT * FROM tbl USING SAMPLE 20% (system, 377); Select a...sample of approximately 20% of tbl before the join with tbl2 : SELECT * FROM tbl TABLESAMPLE reservoir(20%), tbl2 WHERE tbl.i = tbl2.i; Select a s... - https://man.mtool.work/duckdb/2.0/sql/samples.html
- File Formats 9475
- 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
...to perform quite well when run on Parquet files. Storage considerations: Loading the data from Parquet files will require approximately the same amount of space for the DuckDB database file. Therefore, if the available disk space is constrained, it is worth...sion 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. Bestpractice If you have the storage space available, and have... - https://man.mtool.work/duckdb/2.0/guides/performance/file_formats.html
- Working with Huge Databases 9475
- This page contains information for working with huge DuckDB database files. While most DuckDB databases are well below 1 TB, in our 2024 user survey , 1% of respondents used DuckDB files of 2 TB or more (corresponding to roughly 10 TB of CS
...kDB database can be slow. For example, checkpointing after adding a few rows to a table in the TPC-H SF1000 database takes approximately 5 seconds. On block-based storage, the file system has a significant effect on performance when working with large files.... - https://man.mtool.work/duckdb/2.0/guides/performance/working_with_huge_databases...
- Parquet Encryption 8813
- Starting with version 0.10.0, DuckDB supports reading and writing encrypted Parquet files. DuckDB broadly follows the Parquet Modular Encryption specification with some limitations . Reading and Writing Encrypted Files Using the PRAGMA add_
...from/to a Parquet file takes 0.26 and 0.99 seconds, respectively. With encryption, this takes 0.64 and 2.21 seconds, both approximately 2.5× slower than the unencrypted version.... - https://man.mtool.work/duckdb/2.0/data/parquet/encryption.html
- Join Operations 8813
- How to Force a Join Order DuckDB has a cost-based query optimizer, which uses statistics in the base tables (stored in a DuckDB database or Parquet files) to estimate the cardinality of operations. Turn off the Join Order Optimizer To turn
...The approximate_join_order_threshold setting controls when this happens: joins with at least this many tables are ordered approximately, while joins with fewer tables are ordered exactly. The default value is 12. For example, to use the exact algorithm for j... - https://man.mtool.work/duckdb/2.0/guides/performance/join_operations.html
- Numeric Types 8813
- Fixed-Width Integer Types The types TINYINT , SMALLINT , INTEGER , BIGINT and HUGEINT store whole numbers, that is, numbers without fractional components, of various ranges. Attempts to store values outside of the allowed range will result
...types, but uses three additional bytes to store the required size and a sign bit. A number with N decimal digits requires approximately 0.415 * N + 3 bytes when stored in a BIGNUM . Unlike variable-length integer implementations in other systems, there are l...imits to BIGNUM : the maximal and minimal representable values are approximately ±4.27e20201778 . Those are numbers with 20,201,779 decimal digits and storing a single such number requires 8 megabytes. F... - https://man.mtool.work/duckdb/2.0/sql/data_types/numeric.html
- Unofficial and Unsupported Platforms 8384
- Warning The platforms listed on this page are not officially supported. The build instructions are provided on a best-effort basis. Community contributions are very welcome. DuckDB is built and distributed for several platforms with differe
...thub.com/duckdb/duckdb cd duckdb mkdir build && cd build cmake .. -DCMAKE_BUILD_TYPE=Release make -j$(nproc) Build time is approximately 2 hours on an 8-core SpacemiT K1. The resulting binary works out of the box: ./duckdb -c “SELECT 'Hello from RISC-V' AS me... - https://man.mtool.work/duckdb/2.0/dev/building/unofficial_and_unsupported_platfo...
- Release Cycle 7490
- This document outlines the DuckDB and core extension release cycle framework. It is intended for developers working on DuckDB extensions to better understand the underlying processes. Overview DuckDB follows Semantic Versioning ( v<MAJOR>.<
...MINOR>.<PATCH> ) Feature releases (new minor or major versions) are released approximately every 6 months, e.g., v1.4.0 in September 2025, v1.5.0 in March 2026 and v2.0.0 in October 2026 Patch releases are issued... - https://man.mtool.work/duckdb/2.0/dev/release_cycle.html
- Configuration 7276
- DuckDB has a number of configuration options that can be used to change the behavior of the system. The configuration options can be set using either the SET statement or the PRAGMA statement . They can be reset to their original values usi
.... VARCHAR[] [] approximate_join_order_threshold The minimum number of tables in a join to determine the optimal join order approximately instead of exactly. UBIGINT 12 arrow_large_buffer_size Whether Arrow buffers for strings, blobs, UUIDs and bits should be... - https://man.mtool.work/duckdb/2.0/configuration/overview.html
- Aggregate Functions 7043
- Examples Produce a single row containing the sum of the amount column: SELECT sum(amount) FROM sales; Produce one row per unique region, containing the sum of amount for each group: SELECT region, sum(amount) FROM sales GROUP BY region; Ret
...alculates the approximate quantile using T-Digest. approx_quantile(A, 0.5) approx_top_k(arg, k) Calculates a LIST of the k approximately most frequent values of arg using Filtered Space-Saving. reservoir_quantile(x, quantile, sample_size = 8192) Calculates th... - https://man.mtool.work/duckdb/2.0/sql/functions/aggregates.html
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