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785d45e012
firebird-mirror/doc/sql.extensions/README.sql_package.md
Adriano dos Santos Fernandes 39b019574a
Feature #7675 - EXPLAIN statement and RDB$SQL package. (#7697) 
* Feature #7675 - EXPLAIN statement and RDB$SQL package.

* Change ObjectsArray::back() to match STL semantics and add front() method.

* Fix indentation problem.

* Add OBJECT_TYPE column.

* Add CARDINALITY column.

* Add conversion from bid to ISC_QUAD.

* Replace fb_assert by static_assert.

* Change ACCESS_PATH output parameter to blob.

* Improve docs.
2023-09-18 21:52:20 -03:00

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RDB$SQL package (FB 6.0)

RDB$SQL is a package with utility routines to work with dynamic SQL.

Procedure EXPLAIN

RDB$SQL.EXPLAIN returns tabular information of a query's plan, without execute the query.

Since SQL text generally is multi-line string and have quotes, you may use <alternate string literal> (strings prefixed by Q) as a way to make escape easy.

Input parameters:

  • SQL type BLOB SUB_TYPE TEXT CHARACTER SET UTF8 NOT NULL - query statement

Output parameters:

  • PLAN_LINE type INTEGER NOT NULL - plan's line order
  • RECORD_SOURCE_ID type BIGINT NOT NULL - record source id
  • PARENT_RECORD_SOURCE_ID type BIGINT - parent record source id
  • LEVEL type INTEGER NOT NULL - indentation level (may have gaps in relation to parent's level)
  • PACKAGE_NAME type RDB$PACKAGE_NAME - package name of a stored procedure
  • OBJECT_NAME type RDB$RELATION_NAME - object (table, procedure) name
  • ALIAS type RDB$RELATION_NAME - alias name
  • RECORD_LENGTH type INTEGER - record length for the record source
  • KEY_LENGTH type INTEGER - key length for the record source
  • ACCESS_PATH type VARCHAR(255) CHARACTER SET UTF8 NOT NULL - friendly plan description
select *
  from rdb$sql.explain('select * from employees where id = ?');

select *
  from rdb$sql.explain(q'{
    select *
    from (
      select name from employees
      union all
      select name from customers
    )
    where name = ?
  }');

Authors

  • Adriano dos Santos Fernandes