Function to get the correct comparison function.

the data necessary to convert a TermTree into a machine to calculate the result of the term.

describes one chain of joins.

represents parts of expressions if left is != nil: leaf is nil, operator is >= 0 if right is nil, operator is unary (NOT) if leaf is != nil then operator is -1 and left and right are nil.

describes a table expression in the From-Part including the preceding jointype, if there is one.

represents the view on the table used for joining, isOuter defines, that table should be outer-joined values represents the view records where the first Value in the records represents the internal record-Id (as int64) if there is one.

initialized by From-Expression starts delivering Joined View of Record which is base of select-statement allows conversion of GoSqlIdentifier to index so that machine can access attributes by index Next-Operation iterates through valid.