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- Relational API on Pandas 12777
- DuckDB offers a relational API that can be used to chain together query operations. These are lazily evaluated so that DuckDB can optimize their execution. These operators can act on Pandas DataFrames, DuckDB tables or views (which can poin
...ations are not yet executed) # equivalent to: SELECT i, j, i*2 AS two_i FROM input_df WHERE i >= 2 ORDER BY i DESC LIMIT 2 transformed_rel = rel.filter('i >= 2').select('i, j, i*2 AS two_i').order('i DESC').limit(2) # trigger execution by requesting .df() o...f the relation # .df() could have been added to the end of the chain above - it was separated for clarity output_df = transformed_rel.df() Relational operators can also be used to group rows, aggregate, find distinct combinations of values, join, union... - https://man.mtool.work/duckdb/2.0/guides/python/relational_api_pandas.html
- SELECT Clause 10214
- The SELECT clause specifies the list of columns that will be returned by the query. While it appears first in the clause, logically the expressions here are executed only at the end. The SELECT clause can contain arbitrary expressions that
...ith arrays , lists , or structs . The unnest function strips one level of nesting from the type. For example, INTEGER[] is transformed into INTEGER . STRUCT(a INTEGER, b INTEGER) is transformed into a INTEGER, b INTEGER . The unnest function can be used to... - https://man.mtool.work/duckdb/2.0/sql/query_syntax/select.html
- Overview of DuckDB Internals 8797
- 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
...sents what kind of statement it is (e.g., StatementType::SELECT represents a SELECT statement). A single SQL string can be transformed into multiple SQL statements in case the original query string contains multiple queries. Binder The binder converts all n... - https://man.mtool.work/duckdb/2.0/internals/overview.html
- CASE Expression 8797
- The CASE expression performs a switch based on a condition. The basic form is identical to the ternary condition used in many programming languages ( CASE WHEN cond THEN a ELSE b END is equivalent to cond ? a : b ). With a single condition
...rovide an individual expression after the CASE but before the WHEN . When this is done, the CASE expression is effectively transformed into a switch statement. CREATE OR REPLACE TABLE integers AS SELECT unnest([1, 2, 3]) AS i; SELECT i, CASE i WHEN 1 THEN 1... - https://man.mtool.work/duckdb/2.0/sql/expressions/case.html
- Geometry Data Type 8233
- Name Description GEOMETRY Geospatial entity The GEOMETRY data type is used to store and manipulate geometric objects, such as points, lines, and polygons. The GEOMETRY type was part of the spatial extension but became a built-in data type i
...der SET geometry_always_xy = true; SELECT ST_Transform('POINT(4.897070 52.377956)'::GEOMETRY('OGC:CRS84'), 'EPSG:3857') AS transformed; ---- ┌────────────────────────────────────────────┐ │ transformed │ │ geometry('epsg:3857') │ ├──────────────────────────... - https://man.mtool.work/duckdb/2.0/sql/data_types/geometry.html
- Indexes 8233
- Index Types DuckDB has two built-in index types. Indexes can also be defined via extensions . Min-Max Index (Zonemap) A min-max index (also known as zonemap or block range index) is automatically created for columns of all general-purpose d
...straint Checking in UPDATE Statements UPDATE statements on indexed columns and columns that cannot be updated in place are transformed into a DELETE of the original row followed by an INSERT of the updated row. This rewrite has performance implications, par... - https://man.mtool.work/duckdb/2.0/sql/indexes.html
- Relational API 6525
- The Relational API builds a query one step at a time from Python. A relation, a DuckDBPyRelation , is a piece of SQL text: the methods of the Transformation and Functions sections return a new relation whose text extends the one they were c
...passed function on the relation. Parameters map_function : Callable A Python function that takes a DataFrame and returns a transformed DataFrame. * schema : dict, keyword-only, default: None The columns of the output relation, as a dict of name to type. Wit... - https://man.mtool.work/duckdb/2.0/clients/python/relational_api.html
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