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- Julia Client 13553
- 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
...ulia threads/tasks for this purpose. If you wish to run queries in parallel, you must launch Julia with multi-threading support (by e.g., se...uckDB.end_row(appender) end # close the appender after all rows DuckDB.close(appender) Concurrency Within a Julia process, tasks are able to concurrently read and write to the database, as long as each task maintains its own connection to the databas...e. In the example below, a single task is spawned to periodically read the database and many tasks are spawned to write to the database using both INSERT stateme... - https://man.mtool.work/duckdb/2.0/clients/tertiary_clients/julia.html
- Complete API 10371
- This page contains the reference for DuckDB's C API. The reference contains several deprecation notices. These concern methods whose long-term availability is not guaranteed as they may be removed in the future. That said, DuckDB's develope
...); const char * duckdb_pending_error ( duckdb_pending_result pending_result ); duckdb_pending_state duckdb_pending_execute_task ( duckdb_pending_result pending_result ); duckdb_pending_state duckdb_pending_execute_check_state ( duckdb_pending_result...ow_schema , duckdb_arrow_array arrow_array , duckdb_arrow_stream * out_stream ); Threading Information void duckdb_execute_tasks ( duckdb_database database , idx_t max_tasks ); duckdb_task_state duckdb_create_task_state ( duckdb_database database );...void duckdb_execute_tasks_state ( duckdb_task_state state ); idx_t duckdb_execute_n_tasks_state ( duckdb_task_state state , idx_t max_tasks ); void... - https://man.mtool.work/duckdb/2.0/clients/c/api.html
- My Workload Is Slow 8915
- If you find that your workload in DuckDB is slow, we recommend performing the following checks. More detailed instructions are linked for each point. Do you have enough memory? DuckDB works best if you have 1-4 GB memory per thread . Is you
...he query plan look right? Study it with EXPLAIN . Is the workload running in parallel ? Use htop or the operating system's task manager to observe this. Is DuckDB using too many threads? Try limiting the amount of threads . Are you aware of other com... - https://man.mtool.work/duckdb/2.0/guides/performance/my_workload_is_slow.html
- PostgreSQL Extension 8484
- The postgres extension allows DuckDB to directly read and write data from a running PostgreSQL database instance. The data can be queried directly from the underlying PostgreSQL database. Data can be loaded from PostgreSQL tables into DuckD
...ken for PostgreSQL OAUTHBEARER authentication. Takes priority over the PGOAUTHTOKEN environment variable NULL pg_pages_per_task The amount of pages per task 1000 pg_query_mode Query mode used to read data, one of 'AUTO' , 'COPY_BINARY' , 'PLAIN_QUERY... - https://man.mtool.work/duckdb/2.0/core_extensions/postgres/overview.html
- I/O 8052
- Warning DuckDB ships with safe defaults. The configuration options described on this page are advanced options, so proceed with caution when changing them. Asynchronous I/O New Asynchronous I/O was introduced in DuckDB 2.0. Starting with v2
...eads setting and defaults to the number of CPU cores. Regular threads prioritize query processing but can also perform I/O tasks when idle. The asynchronous pool contains threads dedicated to blocking I/O. As these threads spend most of their time wa...hreads fetch the data for the next jobs. If the data for a job has not arrived yet, the worker thread is free to run other tasks in the meantime. Keeping more fetch tasks in flight consumes more memory. To determine a budget and avoid out-of-memory i...unlimited depth, bounded by memory. N > 0 : at most N jobs ahead, with no memory budget. 0 : read-ahead is off, each scan task schedules I/O only for its own job. To configure it, use the SET clause, e.g.: SET read_ahead_depth = 5; In the default mo... - https://man.mtool.work/duckdb/2.0/data/io.html
- Enum Data Type 8052
- Name Description ENUM Dictionary representing all possible string values of a column The enum type represents a dictionary data structure with all possible unique values of a column. For example, a column storing the days of the week can be
...ng (as described in the previous section), and the comparison will be done lexicographically as with strings: CREATE TABLE tasks (name TEXT, priority_level priority); INSERT INTO tasks VALUES ('a', 'low'), ('b', 'medium'), ('c', 'high'); -- WARNING!...-- Equivalent to `WHERE priority_level::VARCHAR >= 'medium'` SELECT * FROM tasks WHERE priority_level >= 'medium'; -- Misses the 'high' priority task! name priority_level b medium So, if you want to e.g.... "get all priorities at or above medium " then explicitly cast to the enum type: SELECT * FROM tasks WHERE priority_level >= 'medium'::priority; name priority_level b medium c high Functions See Enum Functions . For exampl... - https://man.mtool.work/duckdb/2.0/sql/data_types/enum.html
- Friendly SQL 8052
- DuckDB offers several advanced SQL features and syntactic sugar to make SQL queries more concise. We refer to these colloquially as “friendly SQL”. Several of these features were first introduced by DuckDB, while some are inspired by other
...'hello world' AS z, ; "Top-N in Group" Queries Computing the "top-N rows in a group" ordered by some criteria is a common task in SQL that unfortunately often requires a complex query involving window functions and/or subqueries. To aid in this, Duc... - https://man.mtool.work/duckdb/2.0/sql/dialect/friendly_sql.html
- CSV Import 7747
- Examples The following examples use the flights.csv file. Read a CSV file from disk, auto-infer options: SELECT * FROM 'flights.csv'; Use the read_csv function with custom options: SELECT * FROM read_csv('flights.csv', delim = '|', header =
...s.csv'; CSV Loading CSV loading, i.e., importing CSV files to the database, is a very common, and yet surprisingly tricky, task. While CSVs seem simple on the surface, there are a lot of inconsistencies found within CSV files that can make loading th... - https://man.mtool.work/duckdb/2.0/data/csv/overview.html
- Configuration 7603
- 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 512.0 MiB allocator_flush_threshold Peak allocation threshold at which to flush the allocator after completing a task. VARCHAR 134217728B allow_asterisks_in_http_paths Allow '*' character in URLs users can query BOOLEAN false allow_communit...an ASOF join to use a nested loop join. UBIGINT 64 async_threads The number of total async threads used by the system for tasks like I/O. BIGINT 4 × # CPU cores (max. 256) auto_checkpoint_skip_wal_threshold The estimated WAL write size at which poin...rather than re-fetched from the source. BOOLEAN false external_threads The number of external threads that work on DuckDB tasks. UBIGINT 1 extra_http_headers Extra HTTP headers added to every request MAP(VARCHAR, VARCHAR) {} file_search_path A comma... - https://man.mtool.work/duckdb/2.0/configuration/overview.html
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