Concatenate two strings using ||

"portable" concat for backends that do not have a native concat function.

Basic aggregations

Distinct count of expression

Function calls and common control flow

Basic arithmetic

Type casts

Logical operators

Higher level combinators and utilities

sum 1

Replace exp if its equal to val with replace.

Set to null unless predicate in first argument is true

Set to null if predicate in first argument is true

Make empty string NULL.

Apply a function on Literals and Vars, recursing deep into function calls, etc.

Common case of a string column possibly being empty either by being a blank string or properly being NULL.

Opposite of isEmpty

(Agg) Count number of Trues in a boolean expression.

True -> 1, False -> 0, NULL -> 0

returns the first non-null value in the arguments list.

Apply a given predicate condition deeply within a given expression, such that the predicate is pushed inside all the aggregating function calls in SQL.

This makes it possible to have conditional aggregations without needing additional CTEs.

TODO. This is may have holes; we need a principled end-to-end review of this transformation. Perhaps even put it as a primitive into the SExp type.

Infer aggregation level of an expression.

TODO: ExternRaw and NativeExpr cant be inferred at the moment; needs more info inside the SExp if this becomes a problem.

Explore expression's insides to pull out top level Unit expressions within its branches, but no deeper in each branch.

Originally created to help with common expression caching - since you can commonolize unit-level expressions without any side-effect.