Package net.hydromatic.morel.ast

Class FromBuilder

java.lang.Object

net.hydromatic.morel.ast.FromBuilder

public class FromBuilder
extends Object

Builds a Core.From.

Simplifies the following patterns:

• Converts "from v in list" to "list" (only works in buildSimplify(), not build());
• Removes "where true" steps;
• Removes empty "order" steps;
• Removes trivial yield, e.g. "from v in list where condition yield v" becomes "from v in list where condition";
• Inlines from expressions, e.g. "from v in (from w in list)" becomes "from w in list yield {v = w}".

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private class	FromBuilder.StepHandler	Calls the method to re-register a step.
private static enum	FromBuilder.TupleType	Category of expression passed to "yield".

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	atom
private final List<Binding>	bindings
private final @Nullable Environment	env
private int	removeIfLastIndex	If non-negative, flags that particular step should be removed if it is the last step.
private int	removeIfNotLastIndex	If non-negative, flags that particular step should be removed if it is not the last step.
private final List<Core.FromStep>	steps
private final TypeSystem	typeSystem

Constructor Summary

Constructors

Constructor	Description
FromBuilder(TypeSystem typeSystem, @Nullable Environment env)	Use CoreBuilder.fromBuilder(net.hydromatic.morel.type.TypeSystem, net.hydromatic.morel.compile.Environment).

Method Summary

Modifier and Type	Method	Description
FromBuilder	addAll(Iterable<? extends Core.FromStep> steps)
private FromBuilder	addStep(Core.FromStep step)
Core.From	build()
private Core.Exp	build(boolean simplify)
Core.Exp	buildSimplify()	As build(boolean), but also simplifies "from x in list" to "list".
void	clear()	Resets state as if this FromBuilder had just been created.
private static boolean	containsOrdinal(Core.Exp exp)	Returns whether a expression calls ordinal.
FromBuilder	distinct()
FromBuilder	except(boolean distinct, List<Core.Exp> args)
FromBuilder	group(SortedMap<Core.IdPat,Core.Exp> groupExps, SortedMap<Core.IdPat,Core.Aggregate> aggregates)
FromBuilder	intersect(boolean distinct, List<Core.Exp> args)
private static boolean	isSimplePat(Core.Pat pat, Core.From exp)
private static boolean	isTrivial(Core.Tuple tuple, Core.StepEnv env, @Nullable Core.StepEnv env2)	Returns whether tuple is something like "{i = i, j = j}".
FromBuilder	order(Core.Exp exp)
FromBuilder	scan(Core.Pat pat)	Creates an unbounded scan, "from pat".
FromBuilder	scan(Core.Pat pat, Core.Exp exp)	Creates a bounded scan, "from pat in exp".
FromBuilder	scan(Core.Pat pat, Core.Exp exp, Core.Exp condition)
FromBuilder	skip(Core.Exp count)
Core.StepEnv	stepEnv()	Returns the environment available after the most recent step.
FromBuilder	take(Core.Exp count)
String	toString()
private static FromBuilder.TupleType	tupleType(Core.Tuple tuple, Core.StepEnv env, @Nullable Core.StepEnv env2)	Returns whether tuple is something like "{i = i, j = j}".
FromBuilder	union(boolean distinct, List<Core.Exp> args)
FromBuilder	unorder()
FromBuilder	where(Core.Exp condition)
FromBuilder	yield_(boolean uselessIfLast, @Nullable Core.StepEnv env2, Core.Exp exp, boolean atom)	Creates a "yield" step.
FromBuilder	yield_(boolean uselessIfLast, Core.Exp exp, boolean atom)
FromBuilder	yield_(Core.Exp exp)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

typeSystem

private final TypeSystem typeSystem

env

private final @Nullable Environment env

steps

private final List<Core.FromStep> steps

bindings

private final List<Binding> bindings

atom

private boolean atom

removeIfNotLastIndex

private int removeIfNotLastIndex

If non-negative, flags that particular step should be removed if it is not the last step. (For example, "yield {i = i}", which changes the result shape if the last step but is otherwise a no-op.)

removeIfLastIndex

private int removeIfLastIndex

If non-negative, flags that particular step should be removed if it is the last step. (For example, we flatten "from p in (from q in list)", to "from q in list yield {p = q}" but we want to remove "yield {p = q}" if it turns out to be the last step.)

Constructor Details

FromBuilder

FromBuilder(TypeSystem typeSystem,
 @Nullable Environment env)

Use CoreBuilder.fromBuilder(net.hydromatic.morel.type.TypeSystem, net.hydromatic.morel.compile.Environment).

Method Details

clear

public void clear()

Resets state as if this FromBuilder had just been created.

toString

public String toString()

Overrides:

toString in class Object

stepEnv

public Core.StepEnv stepEnv()

Returns the environment available after the most recent step.

addStep

private FromBuilder addStep(Core.FromStep step)

scan

public FromBuilder scan(Core.Pat pat)

Creates an unbounded scan, "from pat".

scan

public FromBuilder scan(Core.Pat pat,
 Core.Exp exp)

Creates a bounded scan, "from pat in exp".

scan

public FromBuilder scan(Core.Pat pat,
 Core.Exp exp,
 Core.Exp condition)

containsOrdinal

private static boolean containsOrdinal(Core.Exp exp)

Returns whether a expression calls ordinal.

isSimplePat

private static boolean isSimplePat(Core.Pat pat,
 Core.From exp)

addAll

public FromBuilder addAll(Iterable<? extends Core.FromStep> steps)

where

public FromBuilder where(Core.Exp condition)

skip

public FromBuilder skip(Core.Exp count)

take

public FromBuilder take(Core.Exp count)

except

public FromBuilder except(boolean distinct,
 List<Core.Exp> args)

intersect

public FromBuilder intersect(boolean distinct,
 List<Core.Exp> args)

union

public FromBuilder union(boolean distinct,
 List<Core.Exp> args)

unorder

public FromBuilder unorder()

distinct

public FromBuilder distinct()

group

public FromBuilder group(SortedMap<Core.IdPat,Core.Exp> groupExps,
 SortedMap<Core.IdPat,Core.Aggregate> aggregates)

order

public FromBuilder order(Core.Exp exp)

yield_

public FromBuilder yield_(Core.Exp exp)

yield_

public FromBuilder yield_(boolean uselessIfLast,
 Core.Exp exp,
 boolean atom)

yield_

public FromBuilder yield_(boolean uselessIfLast,
 @Nullable Core.StepEnv env2,
 Core.Exp exp,
 boolean atom)

Creates a "yield" step.

When copying, the env2 parameter is the Core.FromStep.env value of the current Yield, so that we don't generate new variables (with different ordinals). Later steps are relying on the variables remaining the same. For example, in

 from ... yield {a = b} where a > 5
 

the a in a > 5 references IdPat('a', 0) and we don't want yield to generate an IdPat('a', 1).

Parameters:

uselessIfLast - Whether this Yield will be useless if it is the last step. The expression {x = y} is an example of this

env2 - Desired step environment, or null

exp - Expression to yield

atom - Whether the expression is an atom (as opposed to a record); all atoms have just one binding, but records may also have one binding

Returns:

This FromBuilder, with a Yield added to the list of steps

isTrivial

private static boolean isTrivial(Core.Tuple tuple,
 Core.StepEnv env,
 @Nullable Core.StepEnv env2)

Returns whether tuple is something like "{i = i, j = j}".

tupleType

private static FromBuilder.TupleType tupleType(Core.Tuple tuple,
 Core.StepEnv env,
 @Nullable Core.StepEnv env2)

Returns whether tuple is something like "{i = i, j = j}".

build

private Core.Exp build(boolean simplify)

build

public Core.From build()

buildSimplify

public Core.Exp buildSimplify()

As build(boolean), but also simplifies "from x in list" to "list".