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package exprgen

import ""


Package Files

custom_funcs.go expr_gen.go parse_type.go private.go

func Build Uses

func Build(catalog cat.Catalog, factory *norm.Factory, input string) (_ opt.Expr, err error)

Build generates an expression from an optgen string (the kind of expression that would show up in the replace side of a rule).

For example, if the input is "(Eq (Const 1) (Const 2))", the output is the corresponding expression tree:

eq [type=bool]
 ├── const: 1 [type=int]
 └── const: 2 [type=int]

There are some peculiarities compared to the usual opt-gen replace syntax:

- Filters are specified as simply [ <condition> ... ]; no FiltersItem is

- Various implicit conversions are allowed for convenience, e.g. list of
  columns to ColList/ColSet.

- Operation privates (e.g. ScanPrivate) are specified as lists of fields
  of the form [ (FiledName <value>) ]. For example:
    [ (Table "abc") (Index "abc@ab") (Cols "a,b") ]
  Implicit conversions are allowed here for column lists, orderings, etc.

- A Root custom function is used to set the physical properties of the root.
  Setting the physical properties (in particular the presentation) is always
  necessary for the plan to be run via PREPARE .. AS OPT PLAN '..'.

Some examples of valid inputs:

(Tuple [ (True) (False) ] "tuple{bool, bool}" )

  (Scan [ (Table "abc") (Index "abc@ab") (Cols "a,b") ])
  (Presentation "a,b")
  (OrderingChoice "+a,+b")

  (Scan [ (Table "abc") (Cols "a,b,c") ])
  [ (Eq (Var "a") (Const 1)) ]

For more examples, see the various testdata/ files.

func ParseType Uses

func ParseType(typeStr string) (*types.T, error)

ParseType parses a string describing a type. It supports tuples using the syntax "tuple{<type>, <type>, ...}" but does not support tuples of tuples.

Package exprgen imports 23 packages (graph) and is imported by 4 packages. Updated 2020-10-24. Refresh now. Tools for package owners.