The $CONTEXT function is used to retrieve small excerpts from a document containing the search criteria. The $CONTEXT function returns the words adjacent to the criteria, formatting them if requested so that they keywords are easily visible. The $CONTEXT function can return multiple of these contexts in one string, allowing the user to see the various locations which led to an entry being qualified.

The $CONTEXT function is a select list item that retrieves excerpts, or windows, from a document showing the context in which a row matched the qualification criteria from a $CONTAINS criteria predicate. It shows the context in which the search criteria occurred in the document, without the cost of trafficking the entire document. Snippets of the original text, including the keywords and words around it, are returned to the application.

This can prove useful in two ways. First, it allows a distillation of the row to be retrieved without incurring the cost of trafficking large amounts of data. This can make a tremendous difference in the application performance. Second, it provides a concise and convenient method of communicating the essence of the row to the user. A large amount of content is difficult for a user to absorb, but excerpts from a document can be quickly understood.

$CONTEXT is used in conjunction with $CONTAINS, meaning the search criteria MUST be stated in a $CONTAINS function in a WHERE clause predicate. Additionally, a matching label must be specified in both the $CONTEXT and $CONTAINS functions, when the SQL statement contains multiple $CONTAINS criteria predicates.

$CONTEXT[(length [,[‘options’] [,’label’]])]

An optional parameter that controls the length of the string to be returned. If this parameter is not provided, the default size is 256 bytes.

An optional parameter that controls options for the function. Valid options are:

Limit the number of context excerpts to n.

Render the result in the following style:

TEXT (default)
HTML
NONE

Render the result using the following format:

COMPRESSED (default)
UNCOMPRESSED

Use HTML classes so that HTML Style Sheets can be used to determine highlighting characteristics.

When used with the CLASSES option, use different classes so that each word can have independent highlighting characteristics.

When used with the CLASSES option, use different classes so that derived words can have independent highlighting characteristics than original words. When used without CLASSES, but with STYLE=HTML, use <st> for original words and <em> for derived words.

Control whether tabs, linefeeds and other formatting characters are preserved in the output. Set on ON (default when FORMAT=UNCOMPRESSED) or OFF (default when FORMAT=COMPRESSED).

HTML tag to use to highlight keywords when STYLE=HTML. Defaults to “<strong>”.

HTML tag to use to end the highlighting of keywords when STYLE=HTML. Defaults to the HIGHLIGHT string with an initial backslash, such as “</strong>”. This option is only needed with more complex HIGHLIGHT strings.

An optional label that describes this particular search. This label is not needed unless multiple $CONTAINS functions are used in the SQL statement. This label refers to the label used in the $CONTAINS function. The label is case-insensitive, and may be up to 32 characters long.