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- Lambda Functions 14161
- 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
...mbda(x)) Alias for list_transform . array_filter(list, lambda(x)) Alias for list_filter . array_reduce(list, lambda(x,y)[, initial_value]) Alias for list_reduce . array_transform(list, lambda(x)) Alias for list_transform . filter(list, lambda(x)) Alias...The return type of list_filter is the same as the input list's. 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 re...sult and the next list element. The lambda function has an optional initial_value argument. See list_reduce examples . list_transform(list, lambda(x)) Returns a list that is the result of applying t... - https://man.mtool.work/duckdb/2.0/sql/functions/lambda.html
- WITH Clause 10730
- 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.
...ementation, see the “How DuckDB Runs Recursive CTEs Faster” blog post . Using VALUES You can use the VALUES clause for the initial (anchor) part of the CTE: WITH RECURSIVE tbl(a, b) USING KEY (a) AS ( VALUES (1, 3), (2, 4) UNION ALL SELECT a + 1, b FROM...EY (id) AS ( SELECT n.id, n.id AS comp FROM nodes AS n UNION ALL ( SELECT DISTINCT ON (previous_iter.id) previous_iter.id, initial_iter.comp FROM recurring.connected_components AS previous_iter, connected_components AS initial_iter, edges AS e WHERE ((e....node1id, e.node2id) = (previous_iter.id, initial_iter.id) OR (e.node2id, e.node1id) = (previous_iter.id, initial_iter.id)) AND initial_iter.comp < previous_iter.comp ORDER... - https://man.mtool.work/duckdb/2.0/sql/query_syntax/with.html
- Unit Tester Configuration 9802
- There are three ways of setting options for the unit tester: Command Line Arguments Configuration File Environment Variables Configuration Options List See the Configuration Options List for the full list of available options. Command Line
...ding <none|available|all> Loading strategy for extensions not bundled in --base-config <path> Config file to load and base initial settings on --block-size <num> Block Allocation Size; must be a power of 2 --checkpoint-on-shutdown , --no-checkpoint-on-s...tabase between runs --force-storage Test with persistent storage file --init-script <path> SQL script to execute on init --initial-db <path> Initial database path --keep-home Use $HOME/USERPROFILE instead of the sandboxed temp-dir home --max-test-thread...ing> SQL statements to execute on explicit load --on-new-connection <string> SQL statements to execute on connection --one-initialize Initialize buffers with all 1; also see --zero-initialize --require <extension_name> If the extension is missing: fail... - https://man.mtool.work/duckdb/2.0/dev/sqllogictest/test_configuration.html
- List Functions 9155
- 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 <->
...ement) Alias for list_append . array_push_front(list, element) Prepends element to list . array_reduce(list, lambda(x,y)[, initial_value]) Alias for list_reduce . array_resize(list, size[[, value]]) Alias for list_resize . array_reverse(list) Alias for...ends element to list . list_product(list) Applies aggregate function product to the list . 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 re...sult and the next list element. The lambda function has an optional initial_value argument. See list_reduce examples . list_resize(list, size[[, value]]) Resizes the list to contain size elements. I... - https://man.mtool.work/duckdb/2.0/sql/functions/list.html
- Pivot Internals 8227
- PIVOT Pivoting is implemented as a combination of SQL query re-writing and a dedicated PhysicalPivot operator for higher performance. Each PIVOT is implemented as set of aggregations into lists and then the dedicated PhysicalPivot operator
...ery is re-written again into a set of aggregations into lists. For example: PIVOT cities ON year USING sum(population); is initially translated into: CREATE TEMPORARY TYPE __pivot_enum_0_0 AS ENUM ( SELECT DISTINCT year::VARCHAR FROM cities ORDER BY yea...o populate month , and the double quotes to pull the column values for use in sales . This produces the same result as the initial example: empid dept month sales 1 electronics jan 1 1 electronics feb 2 1 electronics mar 3 1 electronics apr 4 1 electron... - https://man.mtool.work/duckdb/2.0/internals/pivot.html
- Go Client 7964
- The latest stable release of the DuckDB Go client bundles DuckDB 2.0.0. Its own version tag encodes that DuckDB version; see Versioning below. The DuckDB Go client, duckdb-go , is a SQL driver that conforms to Go's built-in database/sql int
...tabase with configuration options. db, err := sql.Open("duckdb", "/path/to/foo.db?access_mode=read_only&threads=4") To run initialization steps, such as SET statements, before the first query, open the database with sql.OpenDB() and a Connector . See Co...Overview — the other client APIs DuckDB provides alongside Go. Acknowledgements We would like to thank Marc Boeker for the initial implementation of the DuckDB Go client and for his continued work on it as part of this joint effort with the DuckDB team.... - https://man.mtool.work/duckdb/2.0/clients/go/overview.html
- Configuration 7964
- 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
...count, index_scan_percentage * total_row_count) rows match, we perform an index scan instead of a table scan. DOUBLE 0.001 initial_column_segment_size The initial memory (in bytes) reserved for the first transient column segment. Must be a power of two.... - https://man.mtool.work/duckdb/2.0/configuration/overview.html
- File Formats 7964
- 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
...taset, it is worth loading the data into DuckDB. The queries will always be somewhat faster, which over time amortizes the initial load time. High decompression times: Some Parquet files are compressed using heavyweight compression algorithms such as gz... - https://man.mtool.work/duckdb/2.0/guides/performance/file_formats.html
- Tuning Workloads 7824
- 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
...unning the same query many times, but with different parameters. When a statement is prepared, it completes several of the initial portions of the query execution process (parsing, planning, etc.) and caches their output. When it is executed, those step... - https://man.mtool.work/duckdb/2.0/guides/performance/how_to_tune_workloads.html
- Quack Remote Protocol 7824
- The Quack extension turns a DuckDB instance into a server that other DuckDB instances (clients) can connect to over HTTP. This page covers the protocol at a glance and walks through basic usage on both sides of the wire. For the full list o
...nd keeps complex types (nested, decimals, intervals, ...) lossless across the wire. Single round-trip per query. After the initial connection handshake, a query needs only one request–response pair. Large results stream back in chunks via follow-up FETC... - https://man.mtool.work/duckdb/2.0/quack/overview.html
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