org.apache.flink.table.expressions.resolver

Class ExpressionResolver

java.lang.Object

org.apache.flink.table.expressions.resolver.ExpressionResolver

@Internal
public class ExpressionResolver
extends Object

Tries to resolve all unresolved expressions such as UnresolvedReferenceExpression or calls such as BuiltInFunctionDefinitions.OVER.

The default set of rules (getAllResolverRules()) will resolve following references:

• flatten '*' and column functions to all fields of underlying inputs
• join over aggregates with corresponding over windows into a single resolved call
• resolve remaining unresolved references to fields, tables or local references
• replace calls to BuiltInFunctionDefinitions.FLATTEN, BuiltInFunctionDefinitions.WITH_COLUMNS, etc.
• performs call arguments types validation and inserts additional casts if possible

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ExpressionResolver.ExpressionResolverBuilder Builder for creating ExpressionResolver.
class	ExpressionResolver.PostResolverFactory Factory for creating resolved expressions after the actual resolution has happened.

Method Summary

Modifier and Type	Method and Description
static List<ResolverRule>	getAllResolverRules() List of rules that will be applied during expression resolution.
static List<ResolverRule>	getExpandingResolverRules() List of rules for (possibly) expanding the list of unresolved expressions.
ExpressionResolver.PostResolverFactory	postResolverFactory() Enables the creation of resolved expressions for transformations after the actual resolution.
List<ResolvedExpression>	resolve(List<Expression> expressions) Resolves given expressions with configured set of rules.
List<Expression>	resolveExpanding(List<Expression> expressions) Resolves given expressions with configured set of rules.
static ExpressionResolver.ExpressionResolverBuilder	resolverFor(TableConfig tableConfig, ClassLoader userClassLoader, TableReferenceLookup tableCatalog, FunctionLookup functionLookup, DataTypeFactory typeFactory, SqlExpressionResolver sqlExpressionResolver, QueryOperation... inputs) Creates a builder for ExpressionResolver.

Methods inherited from class java.lang.Object

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

Method Detail

getExpandingResolverRules

public static List<ResolverRule> getExpandingResolverRules()

List of rules for (possibly) expanding the list of unresolved expressions.

getAllResolverRules

public static List<ResolverRule> getAllResolverRules()

List of rules that will be applied during expression resolution.

resolverFor

public static ExpressionResolver.ExpressionResolverBuilder resolverFor(TableConfig tableConfig,
                                                                       ClassLoader userClassLoader,
                                                                       TableReferenceLookup tableCatalog,
                                                                       FunctionLookup functionLookup,
                                                                       DataTypeFactory typeFactory,
                                                                       SqlExpressionResolver sqlExpressionResolver,
                                                                       QueryOperation... inputs)

Creates a builder for ExpressionResolver. One can add additional properties to the resolver like e.g. GroupWindow or OverWindow. You can also add additional ResolverRule.

Parameters:

tableConfig - general configuration

tableCatalog - a way to lookup a table reference by name

functionLookup - a way to lookup call by name

typeFactory - a way to lookup and create data types

inputs - inputs to use for field resolution

Returns:

builder for resolver

resolve

public List<ResolvedExpression> resolve(List<Expression> expressions)

Resolves given expressions with configured set of rules. All expressions of an operation should be given at once as some rules might assume the order of expressions.

After this method is applied the returned expressions should be ready to be converted to planner specific expressions.

Parameters:

expressions - list of expressions to resolve.

Returns:

resolved list of expression

resolveExpanding

public List<Expression> resolveExpanding(List<Expression> expressions)

Resolves given expressions with configured set of rules. All expressions of an operation should be given at once as some rules might assume the order of expressions.

After this method is applied the returned expressions might contain unresolved expression that can be used for further API transformations.

Parameters:

expressions - list of expressions to resolve.

Returns:

resolved list of expression

postResolverFactory

public ExpressionResolver.PostResolverFactory postResolverFactory()

Enables the creation of resolved expressions for transformations after the actual resolution.