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- ANALYZE Statement 12260
- The ANALYZE statement recomputes the statistics on DuckDB's tables. Usage The statistics recomputed by the ANALYZE statement are only used for join order optimization . It is therefore recommended to recompute these statistics for improved
...join orders, especially after performing large updates (inserts and/or deletes). To recompute the statistics, run: ANALYZE;... - https://man.mtool.work/duckdb/2.0/sql/statements/analyze.html
- Schema 10501
- Types It is important to use the correct type for encoding columns (e.g., BIGINT , DATE , DATETIME ). While it is always possible to use string types ( VARCHAR , etc.) to encode more specific values, this is not recommended. Strings use mor
...ents, their runtimes vary significantly. The results below show that joining on BIGINT columns is approx. 1.8× faster than performing the same join on VARCHAR -typed columns encoding the same value. Join column payload type Join column schema type Example...l for ensuring data integrity but they have a negative effect on load performance as they necessitate building indexes and performing checks. Moreover, they very rarely improve the performance of queries as DuckDB does not rely on these indexes for join an... - https://man.mtool.work/duckdb/2.0/guides/performance/schema.html
- Benchmarks 10057
- For several of the recommendations in our performance guide, we use microbenchmarks to back up our claims. For these benchmarks, we use datasets from the TPC-H benchmark and the LDBC Social Network Benchmark's BI workload . Datasets We use
...are generated with the DuckDB tpch extension . A Note on Benchmarks Running fair benchmarks is difficult , especially when performing system-to-system comparison. When running benchmarks on DuckDB, please make sure you are using the latest version (prefera... - https://man.mtool.work/duckdb/2.0/guides/performance/benchmarks.html
- Data Import 10057
- Recommended Import Methods When importing data from other systems to DuckDB, there are several considerations to take into account. We recommend importing using the following order: For systems which are supported by a DuckDB scanner extens
...ython and Rust APIs. Methods to Avoid If possible, avoid looping row-by-row (tuple-at-a-time) in favor of bulk operations. Performing row-by-row inserts (even with prepared statements) is detrimental to performance and will result in slow load times. Bestp... - https://man.mtool.work/duckdb/2.0/guides/performance/import.html
- Collations 10057
- Collations provide rules for how text should be sorted or compared in the execution engine. Collations are useful for localization, as the rules for how text should be ordered are different for different languages or for different countries
...i and j . For that reason, different collations are supported. The user must choose which collation they want to use when performing sorting and comparison operations. By default, the BINARY collation is used. That means that strings are ordered and compa...0-9), but generally does not make much sense for special unicode characters. It is, however, by far the fastest method of performing ordering and comparisons. Hence it is recommended to stick with the BINARY collation unless required otherwise. The BINARY... - https://man.mtool.work/duckdb/2.0/sql/expressions/collations.html
- DELETE Statement 10057
- The DELETE statement removes rows from the table identified by the table-name. If the WHERE clause is not present, all records in the table are deleted. If a WHERE clause is supplied, then only those rows for which the WHERE clause results
...e Running DELETE does not mean space is reclaimed. In general, rows are only marked as deleted. DuckDB reclaims space upon performing a CHECKPOINT . VACUUM currently does not reclaim space.... - https://man.mtool.work/duckdb/2.0/sql/statements/delete.html
- My Workload Is Slow 9613
- 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
... - https://man.mtool.work/duckdb/2.0/guides/performance/my_workload_is_slow.html
- Directly Read DuckDB Databases 9186
- DuckDB allows directly reading DuckDB files through the read_duckdb function: read_duckdb(⟨'path_to_database'⟩, table_name = ⟨'table_to_read'⟩); Using this function is equivalent to performing the following steps: Attaching to the database
... - https://man.mtool.work/duckdb/2.0/guides/file_formats/read_duckdb.html
- CHECKPOINT Statement 9186
- The CHECKPOINT statement synchronizes data in the write-ahead log (WAL) to the database data file. Examples Synchronize data in the default database: CHECKPOINT; Synchronize data in the specified database: CHECKPOINT file_db; Synchronize da
...any in-progress transactions. Also see the related PRAGMA option for further behavior modification. Reclaiming Space When performing a checkpoint (automatic or otherwise), the space occupied by deleted rows is partially reclaimed. Note that this does not... - https://man.mtool.work/duckdb/2.0/sql/statements/checkpoint.html
- Non-Deterministic Behavior 8298
- Several operators in DuckDB exhibit non-deterministic behavior. Most notably, SQL uses set semantics, which allows results to be returned in a different order. DuckDB exploits this to improve performance, particularly when performing multi-
... - https://man.mtool.work/duckdb/2.0/operations_manual/non-deterministic_behavior.h...
DuckDB 2.0 Documentation / man.mtool.work