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- EXPLAIN: Inspect Query Plans 12134
- EXPLAIN SELECT * FROM tbl; The EXPLAIN statement displays the physical plan, i.e., the query plan that will get executed, and is enabled by prepending the query with EXPLAIN . The physical plan is a tree of operators that are executed in a
...tter physical plan. To demonstrate, see the below example: CREATE TABLE students (name VARCHAR, sid INTEGER); CREATE TABLE exams (eid INTEGER, subject VARCHAR, sid INTEGER); INSERT INTO students VALUES ('Mark', 1), ('Joe', 2), ('Matthew', 3); INSERT I...NTO exams VALUES (10, 'Physics', 1), (20, 'Chemistry', 2), (30, 'Literature', 3); EXPLAIN SELECT name FROM students JOIN exams USING...──────╯ ├──────────────────────────────╮ ╭─ Seq Scan ──┴────────────╮ ╭─ Seq Scan ───┴──────────────╮ │ Table: memory.main.exams │ │ Table: memory.main.students │ │ Type: Sequential Scan │ │ Type: Sequential Scan │ │ Projections: sid │ │ Projections:... - https://man.mtool.work/duckdb/2.0/guides/meta/explain.html
- EXPLAIN ANALYZE: Profile Queries 10479
- Prepending a query with EXPLAIN ANALYZE both pretty-prints the query plan, and executes it, providing run-time performance numbers and the actual cardinality (number of rows produced) for every operator. EXPLAIN ANALYZE SELECT * FROM tbl; N
...Below is an example of running EXPLAIN ANALYZE on a query: CREATE TABLE students (name VARCHAR, sid INTEGER); CREATE TABLE exams (eid INTEGER, subject VARCHAR, sid INTEGER); INSERT INTO students VALUES ('Mark', 1), ('Joe', 2), ('Matthew', 3); INSERT I...NTO exams VALUES (10, 'Physics', 1), (20, 'Chemistry', 2), (30, 'Literature', 3); EXPLAIN ANALYZE SELECT name FROM students JOIN exa...───────┰┒ ╭─ Table Scan ───────────────┚┖───────────────────────────╮ ╭─ Table Scan ─┚┖─────────────╮ │ Table: memory.main.exams │ │ Table: memory.main.students │ │ Type: Sequential Scan │ │ Type: Sequential Scan │ │ Projections: sid │ │ Projections:... - https://man.mtool.work/duckdb/2.0/guides/meta/explain_analyze.html
- Metrics 8365
- DuckDB provides a set of metrics that can be used to monitor the performance and health of the database. Metrics are named ⟨group⟩.⟨metric⟩ , e.g., query.total_time or operator.timing . The set of collected metrics is controlled with the tr
...ects the total query time along with the operator metrics. CREATE TABLE students (name VARCHAR, sid INTEGER); CREATE TABLE exams (eid INTEGER, subject VARCHAR, sid INTEGER); INSERT INTO students VALUES ('Mark', 1), ('Joe', 2), ('Matthew', 3); INSERT I...NTO exams VALUES (10, 'Physics', 1), (20, 'Chemistry', 2), (30, 'Literature', 3); SET enable_profiling = 'json'; SET profiling_outpu...t = '/path/to/file.json'; SET tracked_metrics = ['query.total_time', 'operator.*']; SELECT name FROM students JOIN exams USING (sid) WHERE name LIKE 'Ma%'; The file's content after executing the query: { "operator": [ { "extra_info": {}, "inte... - https://man.mtool.work/duckdb/2.0/dev/metrics.html
- Constraints 7629
- In SQL, constraints can be specified for tables. Constraints enforce certain properties over data that is inserted into a table. Constraints can be specified along with the schema of the table as part of the CREATE TABLE statement . In cert
...tudents (id INTEGER PRIMARY KEY, name VARCHAR); CREATE TABLE subjects (id INTEGER PRIMARY KEY, name VARCHAR); CREATE TABLE exams ( exam_id INTEGER PRIMARY KEY, subject_id INTEGER REFERENCES subjects(id), student_id INTEGER REFERENCES students(id), gra...de INTEGER ); INSERT INTO students VALUES (1, 'Student 1'); INSERT INTO subjects VALUES (1, 'CS 101'); INSERT INTO exams VALUES (1, 1, 1, 10); INSERT INTO exams VALUES (2, 1, 2, 10); Constraint Error: Violates foreign key constraint because ke... - https://man.mtool.work/duckdb/2.0/sql/constraints.html
- Information Schema 7317
- The views in the information_schema are SQL-standard views that describe the catalog entries of the database. These views can be filtered to obtain information about a specific column or table. DuckDB's implementation is based on PostgreSQL
...nt_schema Name of the schema that contains the constraint. VARCHAR 'main' constraint_name Name of the constraint. VARCHAR 'exams_exam_id_fkey' table_catalog Name of the database that contains the table that contains the column that is restricted by th...aint. VARCHAR 'main' table_name Name of the table that contains the column that is restricted by this constraint. VARCHAR 'exams' column_name Name of the column that is restricted by this constraint. VARCHAR 'exam_id' ordinal_position Ordinal position...nt_schema Name of the schema that contains the constraint. VARCHAR 'main' constraint_name Name of the constraint. VARCHAR 'exams_exam_id_fkey' table_catalog Name of the database that contains the table (always the current database). VARCHAR 'my_db' ta... - https://man.mtool.work/duckdb/2.0/sql/meta/information_schema.html
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