A problem occurred in the original way infixes were done in that it was assumed that infix
clauses represented pure functions. While this is true of many UDFs (e.g. CONCAT, GETDATE)
it is certainly not true of many others e.g. RAND(), and most importantly RANK(). For this reason,
the operations that are done in ApplyMap on standard AST Map clauses cannot be done therefore additional
safety checks were introduced there in order to assure this does not happen. In addition to this however,
it is necessary to add this normalization step which inserts Nested AST elements in every map
that contains impure infix. See more information and examples in #1534.
A problem occurred in the original way infixes were done in that it was assumed that infix clauses represented pure functions. While this is true of many UDFs (e.g.
CONCAT,GETDATE) it is certainly not true of many others e.g.RAND(), and most importantlyRANK(). For this reason, the operations that are done inApplyMapon standard ASTMapclauses cannot be done therefore additional safety checks were introduced there in order to assure this does not happen. In addition to this however, it is necessary to add this normalization step which insertsNestedAST elements in every map that contains impure infix. See more information and examples in #1534.