tree 96097d30c93cb341033a71164caf41d6cfee4149
parent b126ffc3b5ad3f924087f7b0628c034fc223a679
author Ruslan Ermilov <ru@nginx.com> 1481208709 +0300
committer Ruslan Ermilov <ru@nginx.com> 1481208709 +0300

Map: the "volatile" parameter.

By default, "map" creates cacheable variables [1].  With this
parameter it creates a non-cacheable variable.

An original idea was to deduce the cacheability of the "map"
variable by checking the cacheability of variables specified
in source and resulting values, but it turned to be too hard.
For example, a cacheable variable can be overridden with the
"set" directive or with the SSI "set" command.  Also, keeping
"map" variables cacheable by default is good for performance
reasons.  This required adding a new parameter.

[1] Before db699978a33f (1.11.0), the cacheability of the
"map" variable could vary depending on the cacheability of
variables specified in resulting values (ticket #1090).
This is believed to be a bug rather than a feature.