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- Julia Client 13318
- The DuckDB Julia package provides a high-performance front-end for DuckDB. Much like SQLite, DuckDB runs in-process within the Julia client, and provides a DBInterface front-end. The package also supports multi-threaded execution. It uses J
...cute(db, "CREATE OR REPLACE TABLE data (date TIMESTAMP, id INTEGER)") function run_reader(db) # create a DuckDB connection specifically for this task conn = DBInterface.connect(db) while true println(DBInterface.execute(conn, "SELECT id, count(date) AS count...conn) end # spawn one reader task Threads.@spawn run_reader(db) function run_inserter(db, id) # create a DuckDB connection specifically for this task conn = DBInterface.connect(db) for i in 1:1000 Threads.sleep(0.01) DuckDB.execute(conn, "INSERT INTO data VA...ert tasks for i in 1:100 Threads.@spawn run_inserter(db, 1) end function run_appender(db, id) # create a DuckDB connection specifically for this task appender = DuckDB.Appender(db, "data") for i in 1:1000 Threads.sleep(0.01) row = (Dates.now(Dates.UTC), id)... - https://man.mtool.work/duckdb/2.0/clients/tertiary_clients/julia.html
- Multiple Python Threads 11344
- This page demonstrates how to simultaneously insert into and read from a DuckDB database across multiple Python threads. This could be useful in scenarios where new data is flowing in and an analysis should be periodically re-run. Note that
...unning raises a ResourceInUseException instead of waiting. def write_from_thread(duckdb_con): # Create a DuckDB connection specifically for this thread local_con = duckdb_con.cursor() # Insert a row with the name of the thread. insert_time is auto-generated....ts (thread_name) VALUES (?) """, (thread_name,)).fetchall() def read_from_thread(duckdb_con): # Create a DuckDB connection specifically for this thread local_con = duckdb_con.cursor() # Query the current row count thread_name = str(current_thread().name) res... - https://man.mtool.work/duckdb/2.0/guides/python/multiple_threads.html
- Overview of DuckDB Internals 9068
- Tip For a detailed explanation of DuckDB internals, see the Design and Implementation of DuckDB Internals ("DiDi") library entry. On this page is a brief description of the internals of the DuckDB engine. Parser The parser converts a query
...y (because of filters that statically evaluate to false). Join Order Optimizer : Reorders joins using dynamic programming. Specifically, the DPhyp algorithm from the paper Dynamic Programming Strikes Back is used. Common Sub Expressions : Extracts common sub... - https://man.mtool.work/duckdb/2.0/internals/overview.html
- Order Preservation 9068
- For many operations, DuckDB preserves the order of rows, similarly to data frame libraries such as Pandas. Example Take the following table for example: CREATE TABLE tbl AS SELECT * FROM (VALUES (1, 'a'), (2, 'b'), (3, 'c')) t(x, y); SELECT
...ed unless explicitly specified in the aggregate function) GROUP BY (neither in- nor output order are guaranteed) ORDER BY (specifically, ORDER BY may not use a stable algorithm ) Scalar subqueries Insertion Order By default, the following components preserve... - https://man.mtool.work/duckdb/2.0/sql/dialect/order_preservation.html
- SQL Quirks 8410
- Like all programming languages and libraries, DuckDB has its share of idiosyncrasies and inconsistencies. Some are vestiges of our feathered friend's evolution; others are inevitable because we strive to adhere to the SQL Standard and specifically
... - https://man.mtool.work/duckdb/2.0/sql/dialect/sql_quirks.html
- MERGE INTO Statement 8410
- The MERGE INTO statement is an alternative to INSERT INTO ... ON CONFLICT that doesn't need a primary key since it allows for a custom match condition. This is a very useful alternative for upserting use cases ( INSERT + UPDATE ) when the d
...ion id name salary UPDATE 3 Sarah 89000.0 DELETE 1 John 105000.0 In some cases, you may want to perform a different action specifically if the source doesn't meet a condition. For example, if we expect that data that is not present on the source shouldn't be... - https://man.mtool.work/duckdb/2.0/sql/statements/merge_into.html
- Samples 8072
- 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
...fixed number of rows. Samples are probabilistic, that is to say, samples can be different between runs unless the seed is specifically specified. Specifying the seed only guarantees that the sample is the same if multi-threading is not enabled (i.e., SET th... - https://man.mtool.work/duckdb/2.0/sql/samples.html
- S3 API Support 7752
- The httpfs extension supports reading/writing/ globbing files on object storage servers using the S3 API. S3 offers a standard API to read and write to remote files (while regular http servers, predating S3, do not offer a common write API)
...my_hmac_access_id⟩', SECRET '⟨my_hmac_secret_key⟩' ); Important : The KEY_ID and SECRET values must be HMAC keys generated specifically for Google Cloud Storage interoperability. These are not the same as regular GCP service account keys or access tokens. Yo... - https://man.mtool.work/duckdb/2.0/core_extensions/httpfs/s3api.html
- Versioning of Extensions 7752
- 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
...-release extensions are the next step up from Unstable extensions. They are tagged with version in the SemVer format, more specifically, those in the v0.y.z format. In semantic versioning, versions starting with v0 have a special meaning: they indicate that... - https://man.mtool.work/duckdb/2.0/extensions/versioning_of_extensions.html
- Struct Data Type 7432
- Conceptually, a STRUCT column contains an ordered list of columns called “entries”. The entries are referenced by name using strings. This document refers to those entry names as keys. Each row in the STRUCT column must have the same keys.
...mparison moves on to the next position. For ordering purposes, a NULL entry is treated as larger than any non- NULL value. Specifically: If every entry of s1 is not distinct from the corresponding entry of s2 (treating two NULL s as equal), then s1 and s2 co... - https://man.mtool.work/duckdb/2.0/sql/data_types/struct.html
DuckDB 2.0 Documentation / man.mtool.work