fix vars table (#276)

Author: steveren

source/reference/system-variables.txt

@@ -17,7 +17,122 @@ Overview
 
 |bi-short| provides the following environment variables:
 
-.. include:: /includes/fact-system-vars.rst
+.. list-table::
+   :widths: 30 10 40 10 10
+   :stub-columns: 1
+   :header-rows: 1
+
+   * - System Variable
+     - Data Type
+     - Description
+     - Default Value (Atlas-hosted)
+     - Default Value (On Premises)
+   * - ``full_pushdown_exec_mode``
+     - boolean
+     - Specifies whether a query error is returned for queries with
+       clauses that aren't fully translated to the MongoDB query language.
+       SQL query predicates are used to filter data returned by the query.
+     - ``0 (false)``
+     - ``0 (false)``
+   * - ``log_level``
+     - integer
+     - Specifies the logging level for |bi-short|:
+
+       - ``-1``: Do not log.
+       - ``0``: Log only messages for database users, such as basic
+         ``mongosqld`` events and state changes.
+       - ``1``: Log messages for database users and ``mongosqld`` administrators.
+       - ``2``: For internal use only.
+     - ``2``
+     - ``0``
+   * - ``max_nested_table_depth``
+     - integer
+     - Specifies the maximum number of unique nested field paths that
+       ``mongosqld`` maps to a relational table for a collection.
+     - ``50``
+     - ``50``
+   * - ``max_num_columns_per_table``
+     - integer
+     - The maximum number of unique fields that ``mongosqld`` maps to
+       relational columns for a collection.
+     - ``1000``
+     - ``1000``
+   * - ``mongodb_max_varchar_length``
+     - integer
+     - Specifies the maximum string length returned for columns using
+       the ``VARCHAR`` data type. A value of ``0`` specifies
+       no limit.
+     - ``0``
+     - ``0``
+   * - ``polymorphic_type_conversion_mode``
+     - string
+     - Determines how |bi-short| evaluates document fields that are
+       specified with multiple data types. For example, ``count``
+       could be a number in one document and a string in another.
+       The data type that |bi-short| selects depends on the value
+       of the ``schema_mapping_mode`` system variable. A value of
+       ``majority`` causes |bi-short| to select the type
+       that appears in the majority of document fields, while a value
+       of ``lattice`` would cause |bi-short| to select string as the
+       data type for ``count``. See :doc:`Cached Sampling </schema/cached-sampling>`
+       for more information.
+
+       Set ``polymorphic_type_conversion_mode`` to one of the following
+       values:
+
+       - ``off``:
+         Queries may fail if you do not explicitly cast
+         document fields that are specified with multiple data types.
+       - ``fast``:
+         |bi-short| converts only document fields that
+         appeared as multiple data types during sampling.
+       - ``safe``:
+         |bi-short| converts all document fields to the data type
+         discovered during sampling, even if the fields do not appear
+         as multiple data types.
+     -  ``off``
+     -  ``off``
+   * - ``sample_refresh_interval_secs``
+     - integer
+     - Specifies how frequently, in seconds, that the |bi-short| schema
+       is updated. A value of ``0`` specifies that the schema is not 
+       refreshed after |bi-short| starts.
+
+       See :doc:`Cached Sampling </schema/cached-sampling>` for more
+       information.
+     - ``0``
+     - ``0``
+   * - ``sample_size``
+     - integer
+     - Specifies how many documents |bi-short| samples when generating
+       its schema. A value of ``0`` specifies that |bi-short| performs
+       a collection scan across all sample :option:`namespaces <mongosqld --sampleNamespaces>`.
+
+       See :doc:`Cached Sampling </schema/cached-sampling>` for more
+       information.
+     - ``100``
+     - ``100``
+   * - ``schema_mapping_mode``
+     - string
+     - Specifies how the MongoDB schema is transformed into a relational
+       schema:
+
+       - ``lattice``: See :doc:`Sampling Type Conflicts </schema/type-conflicts>`
+         for more information. 
+       - ``majority``: |bi-short| assigns the most common data type for
+         a field occuring in a sample.
+
+     - ``lattice``
+     - ``lattice``
+   * - ``type_conversion_mode``
+     - string
+     - Specifies the semantics that |bi-short| uses for type conversions,
+       such as the ``CAST`` function.
+
+       - ``mysql``
+       - ``mongosql``
+     - ``mongosql``
+     - ``mongosql``
 
 Setting System Variables
 ------------------------