Expression Evaluation Module Introduction

Module descritption

Expression evaluation module could do computation for Project/Filter expressions effectively. It provides a runtime expression evaluation API which accepts Substrait based expression representation and Apache Arrow based column format data representation.

SDK API

// validate expression can be evaluated by Cider
bool is_supported = ExpressionValidator::validate(extended_expression);
// compile and prepare runtime context
auto expr_evaluator = std::make_shared<ExpressionEvaluator>(extended_expression, std::make_shared<ExprEvaluatorContext>(allocator));
// return computation result in arrow-array format
struct ArrowArray output_array;
struct ArrowSchema output_schema;
expr_evaluator::eval(input_array, input_schema, output_array, output_schema);
// schema check API for input array
bool is_matched = expr_evaluator::schemaCheck(input_schema, substrait_schema);

Please refer ExpressionEvalExample for detailed usage.

Supported functions

Here is a list of all scalar functions supported in expression evaluation.

Scalar Functions
plus	minus	multiply	devide	mod	gt
lt	equal	not_equal	gte	lte	cast
in	is_distinct_from	is_not_distinct_from	is_null	is_not_null	and
or	not	lower	upper	trim	substring
regexp_replace	regexp_substring	char_length	ltrim	rtrim	split
extract	concat	like	regex_like

For other SQL syntax support, like case…when…, coalesce, IF, time ± intervals, etc, you can refer details under feature.