QueryExpression
===============

.. cpp:class:: pandas::QueryExpression

   Query engine class for expression evaluation.

Example
-------

.. code-block:: cpp

   #include <pandas/pandas.h>
   using namespace pandas;

   // Use QueryExpression
   QueryExpression obj;
   // ... operations ...

Constructors
------------

.. list-table::
   :widths: 55 25 20
   :header-rows: 1

   * - Signature
     - Location
     - Example
   * - ``QueryExpression(const std::string& expr)``
     - pd_query.h:780
     - 

Comparison
----------

.. list-table::
   :widths: 40 20 15 25
   :header-rows: 1

   * - Signature
     - Return Type
     - Location
     - Example
   * - ``Lexer lexer(expr)``
     - Lexer
     - pd_query.h:781
     - 

Other Methods
-------------

.. list-table::
   :widths: 40 20 15 25
   :header-rows: 1

   * - Signature
     - Return Type
     - Location
     - Example
   * - ``void collect_columns(const ASTNode\* node)``
     - void
     - pd_query.h:725
     - 
   * - ``collect_columns(and_node->left.get())``
     - 
     - pd_query.h:761
     - 
   * - ``collect_columns(and_node->right.get())``
     - 
     - pd_query.h:762
     - 
   * - ``collect_columns(or_node->left.get())``
     - 
     - pd_query.h:767
     - 
   * - ``collect_columns(or_node->right.get())``
     - 
     - pd_query.h:768
     - 
   * - ``collect_columns(not_node->operand.get())``
     - 
     - pd_query.h:773
     - 
   * - ``collect_columns(root_.get())``
     - 
     - pd_query.h:785
     - 
   * - ``Parser parser(std::move(tokens))``
     - Parser
     - pd_query.h:783
     - 
   * - ``const std::unordered_set<std::string>& referenced_columns() const``
     - const std::unordered_set<std::string>&
     - pd_query.h:790
     - 
   * - ``const ASTNode\* root() const { return root_.get()``
     - const ASTNode\*
     - pd_query.h:788
     - :ref:`View <example-queryexpression-root-0>`


Code Examples
-------------

The following examples are extracted from the test suite.

.. _example-queryexpression-root-0:

.. dropdown:: root (pd_test_4_all.cpp:4471)
   :class-title: example-dropdown

   .. code-block:: cpp
      :linenos:
      :lineno-start: 4461
      :emphasize-lines: 11

      //
      // Drop-in snippet for pandas_tests/pd_test_repr_mismatch.cpp implementing the
      // reproducers from do/plan_repr_timeseries.md:
      //   1. comp.isocalendar        (DatetimeIndex index-name header missing)
      //   2. resample.base_df        (max_rows=60 truncation footer mismatch)
      //
      // Self-contained standalone harness via REPR_MISMATCH_TIMESERIES_STANDALONE.
      // When folded into pd_test_repr_mismatch.cpp, drop the #ifdef helpers, the
      // main(), and the standalone dispatcher block at the bottom.
      //
      // Run this snippet from the main solution root (D:/Projects/Cpp2) so the
      // relative fixture paths under pandas_tests/data/repr_mismatch/ resolve.
      // Data files holding the seeded np.random.randn(1000,3) columns live in the
      // worktree tree and are loaded via an absolute path.
      //
      // Fixture-truth rule: the plan references expected_*.txt, but pandasCore
      // currently produces the buggy_*.txt bytes; we load buggy_*.txt so the
      // snippet passes on the (buggy) current formatter and flips to FAIL once the
      // formatter is fixed (at which point the fixture switches to expected_*.txt).
      //
      // No `using namespace`. No emojis.