This ticket deals with writing new functionality to scan the lookaside file for a given update with its corresponding read_timestamp. As a means of testing the change, a test case is being written as part of WT-4678.

We will continue to instantiate the page from lookaside when a page that was lookaside evicted needs to be read back into the memory. When searching for a historic value for a record, ie an update that corresponds to an older timestamp, we walk through the update chain on the page trying to locate the visible record. When doing so, if there is/was a lookaside file associated with the page, the search functionality that would be written will be used to locate this entry in the lookaside file as well.

The update found in the memory will be compared to the update from the lookaside search and an assertion raised if they mismatch.