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- Release Cycle 12444
- 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>.<
....<z+1> releases Active branch : A branch that is part of the main release cycle. Either main or vx. -codename where n >= 0 Single branch extension : Extension with 1 active branch. Since main is always an active branch this is always main. This means a...They are, from a release cycle point of view, the most complex. Every version of an unstable API extension only targets a single DuckDB version. This 1:1 tie means that the release cycle of these extensions tends to form a sometimes intricate dance ar...y the main role. We will now define the three types of unstable extensions by looking at their number of active branches . Single branch extensions have only the main active branch Two branch extensions have two active branches: main and vx.y-codename... - https://man.mtool.work/duckdb/2.0/dev/release_cycle.html
- Lambda Functions 10443
- DuckDB lambda functions (a.k.a. 'lambdas' or 'lambda expressions') are expressions that define an inline anonymous function. Lambdas are passed as argument to certain list functions , which evaluate the passed lambda expression against its
.... See list_filter examples . list_reduce(list, lambda(x,y)[, initial_value]) Reduces all elements of the input list into a single scalar value by executing the lambda function on a running result and the next list element. The lambda function has an op...r , filter | list_reduce(list, lambda(x,y)[, initial_value]) | Description | Reduces all elements of the input list into a single scalar value by executing the lambda function on a running result and the next list element. The lambda function has an op...(but you can invoke a macro in the lambda's expression). Deprecated Syntax Deprecated DuckDB 1.3 deprecated the old lambda single arrow syntax ( x -> x + 1 ) in favor of the Python-style syntax ( lambda x : x + 1 ). DuckDB 1.3 also introduced a new set... - https://man.mtool.work/duckdb/2.0/sql/functions/lambda.html
- Concurrency 10099
- Handling Concurrency Single Process In in-process mode, DuckDB has two configurable options for concurrency: Read-write mode: one process can both read and write to the database. Read-only mode: multiple processes can read from the database
...ing a combination of MVCC (Multi-Version Concurrency Control) and optimistic concurrency control (see Concurrency within a Single Process ), but all within that single writer process. The reason for this concurrency model is to allow for the caching of...database catalog, and other items so that subsequent queries on the same connection are faster. Concurrency Model within a Single Process DuckDB supports concurrency within a single process according to the following rules. As long as there are no writ... - https://man.mtool.work/duckdb/2.0/connect/concurrency.html
- Literal Types 9745
- DuckDB has special literal types for representing NULL , integer and string literals in queries. These have their own binding and conversion rules. Prior to DuckDB version 0.10.0, integer and string literals behaved identically to the INTEG
...- 65535 SELECT 1_2.1_2E0_1; -- 121.2 SELECT '0b0_1_0_1'::INTEGER; -- 5 String Literals String literals are delimited using single quotes ( ' , apostrophe) and result in STRING_LITERAL values. Note that double quotes ( " ) cannot be used as string delim...aracter: instead, double quotes are used to delimit quoted identifiers . Implicit String Literal Concatenation Consecutive single-quoted string literals separated only by whitespace that contains at least one newline are implicitly concatenated: SELECT...r at or near "' '" LINE 1: SELECT 'Hello' ' ' 'World' AS greeting; ^ Also note that implicit concatenation only works with single-quoted string literals, and does not work with other kinds of string values. Implicit String Conversion STRING_LITERAL ins... - https://man.mtool.work/duckdb/2.0/sql/data_types/literal_types.html
- Avro Extension 9161
- The avro extension enables DuckDB to read Apache Avro files. The avro extension was released as a community extension in late 2024 and became a core extension in early 2025. The read_avro Function The extension adds a single DuckDB function
...1.avro'); FROM read_avro('s3://⟨your-bucket⟩/⟨some_file⟩.avro'); should "just" work. You can also glob multiple files in a single read call or pass a list of files to the functions: FROM read_avro('some_file_*.avro'); FROM read_avro(['some_file_1.avro'...,"null"] becomes a DuckDB INTEGER , which just happens to be NULL sometimes. Similarly, an Avro union that contains only a single type is converted to the type it contains. For example, an Avro record of the union type ["int"] also becomes a DuckDB INT...d" fields, which are the same as DuckDB STRUCT fields. For more convenient handling, this extension turns the entries of a single top-level record into top-level columns. Implementation Internally, this extension uses the "official" Apache Avro C API ,... - https://man.mtool.work/duckdb/2.0/core_extensions/avro.html
- ATTACH and DETACH Statements 8567
- DuckDB allows attaching to and detaching from database files. Examples Attach the database file.db with the alias inferred from the name ( file ): ATTACH 'file.db'; Attach the database file.db with an explicit alias ( file_db ): ATTACH 'fil
...provided within parentheses following the ATTACH statement. Parameter values can be passed in with or without wrapping in single quotes. Arbitrary expressions may be used for parameter values. Name Description Type Default value READ_ONLY Attach the d..._db; Set the default database schema to new_db.my_schema : USE new_db.my_schema; Resolving Conflicts When providing only a single qualification, the system can interpret this as either a catalog or a schema, as long as there are no conflicts. For examp...ll attached databases instead. While multiple transactions can be active at a time – the system only supports writing to a single attached database in a single transaction. If you try to write to multiple attached databases in a single transaction the... - https://man.mtool.work/duckdb/2.0/sql/statements/attach.html
- Reading Multiple Files 8338
- DuckDB can read multiple files of different types (CSV, Parquet, JSON files) at the same time using either the glob syntax, or by providing a list of files to read. See the combining schemas page for tips on reading files with different sch
...t Read all files that match the glob pattern: SELECT * FROM 'test/*.parquet'; Read three Parquet files and treat them as a single table: SELECT * FROM read_parquet(['file1.parquet', 'file2.parquet', 'file3.parquet']); Read all Parquet files from two sp...**/*.parquet'); Multi-File Reads and Globs DuckDB can also read a series of Parquet files and treat them as if they were a single table. Note that this only works if the Parquet files have the same schema. You can specify which Parquet files you want t...read_parquet function can accept a list of filenames as the input parameter. Read three Parquet files and treat them as a single table: SELECT * FROM read_parquet(['file1.parquet', 'file2.parquet', 'file3.parquet']); Glob Syntax Any file name input to... - https://man.mtool.work/duckdb/2.0/data/multiple_files/overview.html
- IN Operator 7869
- The IN operator checks containment of the left expression inside the collection on the right hand side (RHS). Supported collections on the RHS are tuples, lists, and maps, as well as subqueries that return a single column. The single-column
...true SELECT 'key3' IN MAP {'key1': 50, 'key2': 75}; false IN Subquery The IN operator works with subqueries that return a single column. For example: SELECT 42 IN (SELECT unnest([32, 42, 52]) AS x); true If the subquery returns more than one column, a... - https://man.mtool.work/duckdb/2.0/sql/expressions/in.html
- Struct Data Type 7514
- 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.
...layout. The names of the struct entries are case-insensitive. STRUCT s are typically used to nest multiple columns into a single column, and the nested column can be of any type, including other STRUCT s and LIST s. STRUCT s are similar to PostgreSQL'...e. To create a struct with unnamed entries, use a tuple . Create a struct using the struct_pack function. Note the lack of single quotes around the keys and the use of the := operator: SELECT struct_pack(key1 := 'value1', key2 := 42) AS s; Create a str...LECT a."x space" FROM (SELECT {'x space': 1, 'y': 2, 'z': 3} AS a); Bracket notation may also be used. Note that this uses single quotes ( ' ) since the goal is to specify a certain string key and only constant expressions may be used inside the bracke... - https://man.mtool.work/duckdb/2.0/sql/data_types/struct.html
- Subqueries 7286
- Subqueries are parenthesized query expressions that appear as part of a larger, outer query. Subqueries are usually based on SELECT ... FROM , but in DuckDB other query constructs such as PIVOT can also appear as a subquery. Scalar Subquery
...Scalar subqueries are subqueries that return a single value. They can be used anywhere where an expression can be used. If a scalar subquery returns more than a single value, a...perator ( = ). Such direct comparisons only make sense with scalar subqueries. Scalar expressions can still be compared to single-column subqueries returning multiple rows by specifying a quantifier. Available quantifiers are ALL , ANY and SOME . The q...related subqueries, the subquery uses values from the parent subquery. Conceptually, the subqueries are run once for every single row in the parent query. Perhaps a simple way of envisioning this is that the correlated subquery is a function that is ap... - https://man.mtool.work/duckdb/2.0/sql/expressions/subqueries.html
DuckDB 2.0 Documentation / man.mtool.work