/*! @page schema Schemas

The tables we have seen so far have all had simple key/value pairs for records.  We now explain how to deal with more complex data in WiredTiger.

@section schema_intro Tables, Rows and Columns

A table is a logical representation of data consisting of cells in rows and columns.  For example, a database might have this table.

<table>
<tr><th>EmpId</th><th>Lastname</th><th>Firstname</th><th>Salary</th></tr>
<tr><td>1</td><td>Smith</td><td>Joe</td><td>40000</td></tr>
<tr><td>2</td><td>Jones</td><td>Mary</td><td>50000</td></tr>
<tr><td>3</td><td>Johnson</td><td>Cathy</td><td>44000</td></tr>
</table>

This simple table includes an employee identifier, last name and first name, and a salary.

A row-oriented database would store all of the values in a row together, then the values in the next row, and so on:

<pre>
      1,Smith,Joe,40000;
      2,Jones,Mary,50000;
      3,Johnson,Cathy,44000;
</pre>

A column-oriented database stores all of the values of a column together, then the values of the next column, and so on:

<pre>
      1,2,3;
      Smith,Jones,Johnson;
      Joe,Mary,Cathy;
      40000,50000,44000;
</pre>

WiredTiger supports both storage formats, and can mix and match the storage of columns within a logical table.

Applications describe the format of their data by supplying a schema to WT_SESSION::create.  This specifies how the application's data can be split into fields and mapped onto rows and columns.

@section schema_types Column types

@todo describe types

See @ref packing for a complete list of types.

@section schema_data_access Columns in key and values

@todo Describe how to use WT_CURSOR::get_key, WT_CURSOR::get_value, WT_CURSOR::set_key and WT_CURSOR::set_value to access columns.

@section schema_columns Describing Columns

@todo describe how to add columns to a schema

@section schema_column_groups Storing Groups of Columns Together

@todo define and describe column groups

@section schema_indices Adding an Index

@todo describe how to add indices to a schema

@section schema_mapping Column Storage

@todo describe how to store some columns separately

@section schema_examples Code Samples

The code below is taken from the complete example program @ex_ref{ex_schema.c}.

@dontinclude ex_schema.c
@skip C struct
@until POP_RECORD

@skip open_session
@until conn->close

The code below is taken from the complete example program @ex_ref{ex_call_center.c}.

@dontinclude ex_call_center.c
@skip home
@until CALL

@skip create
@until conn->close

@section schema_advanced Advanced Schemas

- non-relational data such as multiple index keys per row
- application-supplied extractors and collators may need to be registered before recovery can run.
 */