Math functions.

Logic operations.

Bit operations.

Other functions;.

Column reference.

String functions.

Aggregate functions.

Time functions.

Control flow functions.

Other expressions.

Json functions;.

Comparison operations.

Mysql specific types.

Unary operations, children count 1.

Values are encoded bytes.

Arithmatic.

Scalar Function.

Encoded value list.

Casting.

Here we use suffix *Sig* to avoid name conflict.

Bucket is an element of histogram.

ByItem type for group by and order by.

Chunk contains multiple rows data and rows meta.

DAGRequest represents the request that will be handled with DAG mode.

It represents a Executor.

Evaluators should implement evaluation functions for every expression type.

FMSketch is used to count distinct values for columns.

KeyRange is the encoded index key range, low is closed, high is open.

values are all in text format.

RowMeta contains row handle and length of a row.

SampleCollector is used for collect samples and calculate the count and ndv of an column.

SelectRequest works like a simplified select statement.

Response for SelectRequest.