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/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.trino.metadata;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Ordering;
import io.trino.spi.TrinoException;
import io.trino.spi.connector.CatalogHandle;
import io.trino.spi.function.BoundSignature;
import io.trino.spi.function.CatalogSchemaFunctionName;
import io.trino.spi.function.FunctionMetadata;
import io.trino.spi.function.FunctionNullability;
import io.trino.spi.function.Signature;
import io.trino.spi.type.Type;
import io.trino.spi.type.TypeManager;
import io.trino.sql.analyzer.TypeSignatureProvider;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.TreeSet;
import java.util.stream.Collectors;
import static com.google.common.base.MoreObjects.toStringHelper;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.ImmutableList.toImmutableList;
import static com.google.common.collect.Iterables.getOnlyElement;
import static io.trino.spi.StandardErrorCode.AMBIGUOUS_FUNCTION_CALL;
import static io.trino.spi.StandardErrorCode.FUNCTION_IMPLEMENTATION_MISSING;
import static io.trino.spi.StandardErrorCode.FUNCTION_NOT_FOUND;
import static io.trino.spi.function.FunctionKind.SCALAR;
import static io.trino.sql.analyzer.TypeSignatureProvider.fromTypeSignatures;
import static io.trino.type.UnknownType.UNKNOWN;
import static java.lang.String.format;
import static java.util.Collections.nCopies;
import static java.util.Objects.requireNonNull;
/**
* Binds an actual call site signature to a function.
*/
class FunctionBinder
{
private final Metadata metadata;
private final TypeManager typeManager;
public FunctionBinder(Metadata metadata, TypeManager typeManager)
{
this.metadata = requireNonNull(metadata, "metadata is null");
this.typeManager = requireNonNull(typeManager, "typeManager is null");
}
CatalogFunctionBinding bindFunction(List parameterTypes, Collection candidates, String displayName)
{
return tryBindFunction(parameterTypes, candidates).orElseThrow(() -> functionNotFound(displayName, parameterTypes, candidates));
}
Optional tryBindFunction(List parameterTypes, Collection candidates)
{
if (candidates.isEmpty()) {
return Optional.empty();
}
List exactCandidates = candidates.stream()
.filter(function -> function.functionMetadata().getSignature().getTypeVariableConstraints().isEmpty())
.collect(toImmutableList());
Optional match = matchFunctionExact(exactCandidates, parameterTypes);
if (match.isPresent()) {
return match;
}
List genericCandidates = candidates.stream()
.filter(function -> !function.functionMetadata().getSignature().getTypeVariableConstraints().isEmpty())
.collect(toImmutableList());
match = matchFunctionExact(genericCandidates, parameterTypes);
if (match.isPresent()) {
return match;
}
return matchFunctionWithCoercion(candidates, parameterTypes);
}
CatalogFunctionBinding bindCoercion(Signature signature, Collection candidates)
{
// coercions are much more common and much simpler than function calls, so we use a custom algorithm
List exactCandidates = candidates.stream()
.filter(function -> possibleExactCastMatch(signature, function.functionMetadata().getSignature()))
.collect(toImmutableList());
for (CatalogFunctionMetadata candidate : exactCandidates) {
if (canBindSignature(candidate.functionMetadata().getSignature(), signature)) {
return toFunctionBinding(candidate, signature);
}
}
// only consider generic genericCandidates
List genericCandidates = candidates.stream()
.filter(function -> !function.functionMetadata().getSignature().getTypeVariableConstraints().isEmpty())
.collect(toImmutableList());
for (CatalogFunctionMetadata candidate : genericCandidates) {
if (canBindSignature(candidate.functionMetadata().getSignature(), signature)) {
return toFunctionBinding(candidate, signature);
}
}
throw new TrinoException(FUNCTION_IMPLEMENTATION_MISSING, format("%s not found", signature));
}
private boolean canBindSignature(Signature declaredSignature, Signature actualSignature)
{
return new SignatureBinder(metadata, typeManager, declaredSignature, false)
.canBind(fromTypeSignatures(actualSignature.getArgumentTypes()), actualSignature.getReturnType());
}
private static boolean possibleExactCastMatch(Signature signature, Signature declaredSignature)
{
if (!declaredSignature.getTypeVariableConstraints().isEmpty()) {
return false;
}
if (!declaredSignature.getReturnType().getBase().equalsIgnoreCase(signature.getReturnType().getBase())) {
return false;
}
if (!declaredSignature.getArgumentTypes().get(0).getBase().equalsIgnoreCase(signature.getArgumentTypes().get(0).getBase())) {
return false;
}
return true;
}
private Optional matchFunctionExact(List candidates, List actualParameters)
{
return matchFunction(candidates, actualParameters, false);
}
private Optional matchFunctionWithCoercion(Collection candidates, List actualParameters)
{
return matchFunction(candidates, actualParameters, true);
}
private Optional matchFunction(Collection candidates, List parameters, boolean coercionAllowed)
{
List applicableFunctions = identifyApplicableFunctions(candidates, parameters, coercionAllowed);
if (applicableFunctions.isEmpty()) {
return Optional.empty();
}
if (coercionAllowed) {
applicableFunctions = selectMostSpecificFunctions(applicableFunctions, parameters);
checkState(!applicableFunctions.isEmpty(), "at least single function must be left");
}
if (applicableFunctions.size() == 1) {
ApplicableFunction applicableFunction = getOnlyElement(applicableFunctions);
return Optional.of(toFunctionBinding(applicableFunction.function(), applicableFunction.boundSignature()));
}
StringBuilder errorMessageBuilder = new StringBuilder();
errorMessageBuilder.append("Could not choose a best candidate operator. Explicit type casts must be added.\n");
errorMessageBuilder.append("Candidates are:\n");
for (ApplicableFunction function : applicableFunctions) {
errorMessageBuilder.append("\t * ");
errorMessageBuilder.append(function.boundSignature());
errorMessageBuilder.append("\n");
}
throw new TrinoException(AMBIGUOUS_FUNCTION_CALL, errorMessageBuilder.toString());
}
private List identifyApplicableFunctions(Collection candidates, List actualParameters, boolean allowCoercion)
{
ImmutableList.Builder applicableFunctions = ImmutableList.builder();
for (CatalogFunctionMetadata function : candidates) {
new SignatureBinder(metadata, typeManager, function.functionMetadata().getSignature(), allowCoercion)
.bind(actualParameters)
.ifPresent(signature -> applicableFunctions.add(new ApplicableFunction(function, signature)));
}
return applicableFunctions.build();
}
private List selectMostSpecificFunctions(List applicableFunctions, List parameters)
{
checkArgument(!applicableFunctions.isEmpty());
List mostSpecificFunctions = selectMostSpecificFunctions(applicableFunctions);
if (mostSpecificFunctions.size() <= 1) {
return mostSpecificFunctions;
}
Optional> optionalParameterTypes = toTypes(parameters);
if (optionalParameterTypes.isEmpty()) {
// give up and return all remaining matches
return mostSpecificFunctions;
}
List parameterTypes = optionalParameterTypes.get();
if (!someParameterIsUnknown(parameterTypes)) {
// give up and return all remaining matches
return mostSpecificFunctions;
}
// look for functions that only cast the unknown arguments
List unknownOnlyCastFunctions = getUnknownOnlyCastFunctions(applicableFunctions, parameterTypes);
if (!unknownOnlyCastFunctions.isEmpty()) {
mostSpecificFunctions = unknownOnlyCastFunctions;
if (mostSpecificFunctions.size() == 1) {
return mostSpecificFunctions;
}
}
// If the return type for all the selected function is the same, and the parameters are declared as RETURN_NULL_ON_NULL, then
// all the functions are semantically the same. We can return just any of those.
if (returnTypeIsTheSame(mostSpecificFunctions) && allReturnNullOnGivenInputTypes(mostSpecificFunctions, parameterTypes)) {
// make it deterministic
ApplicableFunction selectedFunction = Ordering.usingToString()
.reverse()
.sortedCopy(mostSpecificFunctions)
.get(0);
return ImmutableList.of(selectedFunction);
}
return mostSpecificFunctions;
}
private List selectMostSpecificFunctions(List candidates)
{
List representatives = new ArrayList<>();
for (ApplicableFunction current : candidates) {
boolean found = false;
for (int i = 0; i < representatives.size(); i++) {
ApplicableFunction representative = representatives.get(i);
if (isMoreSpecificThan(current, representative)) {
representatives.set(i, current);
}
if (isMoreSpecificThan(current, representative) || isMoreSpecificThan(representative, current)) {
found = true;
break;
}
}
if (!found) {
representatives.add(current);
}
}
return representatives;
}
private static boolean someParameterIsUnknown(List parameters)
{
return parameters.stream().anyMatch(type -> type.equals(UNKNOWN));
}
private List getUnknownOnlyCastFunctions(List applicableFunction, List actualParameters)
{
return applicableFunction.stream()
.filter(function -> onlyCastsUnknown(function, actualParameters))
.collect(toImmutableList());
}
private boolean onlyCastsUnknown(ApplicableFunction applicableFunction, List actualParameters)
{
List boundTypes = applicableFunction.boundSignature().getArgumentTypes().stream()
.map(typeManager::getType)
.collect(toImmutableList());
checkState(actualParameters.size() == boundTypes.size(), "type lists are of different lengths");
for (int i = 0; i < actualParameters.size(); i++) {
if (!boundTypes.get(i).equals(actualParameters.get(i)) && actualParameters.get(i) != UNKNOWN) {
return false;
}
}
return true;
}
private boolean returnTypeIsTheSame(List applicableFunctions)
{
Set returnTypes = applicableFunctions.stream()
.map(function -> typeManager.getType(function.boundSignature().getReturnType()))
.collect(Collectors.toSet());
return returnTypes.size() == 1;
}
private static boolean allReturnNullOnGivenInputTypes(List applicableFunctions, List parameters)
{
return applicableFunctions.stream().allMatch(x -> returnsNullOnGivenInputTypes(x, parameters));
}
private static boolean returnsNullOnGivenInputTypes(ApplicableFunction applicableFunction, List parameterTypes)
{
FunctionMetadata function = applicableFunction.functionMetadata();
// Window and Aggregation functions have fixed semantic where NULL values are always skipped
if (function.getKind() != SCALAR) {
return true;
}
FunctionNullability functionNullability = function.getFunctionNullability();
for (int i = 0; i < parameterTypes.size(); i++) {
// if the argument value is always null and the function argument is not nullable, the function will always return null
if (parameterTypes.get(i).equals(UNKNOWN) && !functionNullability.isArgumentNullable(i)) {
return true;
}
}
return false;
}
private Optional> toTypes(List typeSignatureProviders)
{
ImmutableList.Builder resultBuilder = ImmutableList.builder();
for (TypeSignatureProvider typeSignatureProvider : typeSignatureProviders) {
if (typeSignatureProvider.hasDependency()) {
return Optional.empty();
}
resultBuilder.add(typeManager.getType(typeSignatureProvider.getTypeSignature()));
}
return Optional.of(resultBuilder.build());
}
/**
* One method is more specific than another if invocation handled by the first method could be passed on to the other one
*/
private boolean isMoreSpecificThan(ApplicableFunction left, ApplicableFunction right)
{
List resolvedTypes = fromTypeSignatures(left.boundSignature().getArgumentTypes());
return new SignatureBinder(metadata, typeManager, right.declaredSignature(), true)
.canBind(resolvedTypes);
}
private CatalogFunctionBinding toFunctionBinding(CatalogFunctionMetadata functionMetadata, Signature signature)
{
BoundSignature boundSignature = new BoundSignature(
new CatalogSchemaFunctionName(
functionMetadata.catalogHandle().getCatalogName(),
functionMetadata.schemaName(),
functionMetadata.functionMetadata().getCanonicalName()),
typeManager.getType(signature.getReturnType()),
signature.getArgumentTypes().stream()
.map(typeManager::getType)
.collect(toImmutableList()));
return new CatalogFunctionBinding(
functionMetadata.catalogHandle(),
bindFunctionMetadata(boundSignature, functionMetadata.functionMetadata()),
SignatureBinder.bindFunction(
functionMetadata.functionMetadata().getFunctionId(),
functionMetadata.functionMetadata().getSignature(),
boundSignature));
}
private static FunctionMetadata bindFunctionMetadata(BoundSignature signature, FunctionMetadata functionMetadata)
{
FunctionMetadata.Builder newMetadata = FunctionMetadata.builder(functionMetadata.getCanonicalName(), functionMetadata.getKind())
.functionId(functionMetadata.getFunctionId())
.signature(signature.toSignature());
functionMetadata.getNames().forEach(newMetadata::alias);
if (functionMetadata.getDescription().isEmpty()) {
newMetadata.noDescription();
}
else {
newMetadata.description(functionMetadata.getDescription());
}
if (functionMetadata.isHidden()) {
newMetadata.hidden();
}
if (!functionMetadata.isDeterministic()) {
newMetadata.nondeterministic();
}
if (functionMetadata.isDeprecated()) {
newMetadata.deprecated();
}
if (functionMetadata.getFunctionNullability().isReturnNullable()) {
newMetadata.nullable();
}
// specialize function metadata to resolvedFunction
List argumentNullability = functionMetadata.getFunctionNullability().getArgumentNullable();
if (functionMetadata.getSignature().isVariableArity()) {
List fixedArgumentNullability = argumentNullability.subList(0, argumentNullability.size() - 1);
int variableArgumentCount = signature.getArgumentTypes().size() - fixedArgumentNullability.size();
argumentNullability = ImmutableList.builder()
.addAll(fixedArgumentNullability)
.addAll(nCopies(variableArgumentCount, argumentNullability.get(argumentNullability.size() - 1)))
.build();
}
newMetadata.argumentNullability(argumentNullability);
return newMetadata.build();
}
static TrinoException functionNotFound(String name, List parameterTypes, Collection candidates)
{
if (candidates.isEmpty()) {
return new TrinoException(FUNCTION_NOT_FOUND, format("Function '%s' not registered", name));
}
Set expectedParameters = new TreeSet<>();
for (CatalogFunctionMetadata function : candidates) {
String arguments = Joiner.on(", ").join(function.functionMetadata().getSignature().getArgumentTypes());
String constraints = Joiner.on(", ").join(function.functionMetadata().getSignature().getTypeVariableConstraints());
expectedParameters.add(format("%s(%s) %s", name, arguments, constraints).stripTrailing());
}
String parameters = Joiner.on(", ").join(parameterTypes);
String expected = Joiner.on(", ").join(expectedParameters);
String message = format("Unexpected parameters (%s) for function %s. Expected: %s", parameters, name, expected);
return new TrinoException(FUNCTION_NOT_FOUND, message);
}
/**
* @param boundSignature Ideally this would be a real bound signature,
* but the resolver algorithm considers functions with illegal types (e.g., char(large_number))
* We could just not consider these applicable functions, but there are tests that depend on
* the specific error messages for these failures.
*/
private record ApplicableFunction(CatalogFunctionMetadata function, Signature boundSignature)
{
public FunctionMetadata functionMetadata()
{
return function.functionMetadata();
}
public Signature declaredSignature()
{
return function.functionMetadata().getSignature();
}
@Override
public String toString()
{
return toStringHelper(this)
.add("declaredSignature", function.functionMetadata().getSignature())
.add("boundSignature", boundSignature)
.toString();
}
}
record CatalogFunctionBinding(CatalogHandle catalogHandle, FunctionMetadata functionMetadata, FunctionBinding functionBinding)
{
CatalogFunctionBinding
{
requireNonNull(catalogHandle, "catalogHandle is null");
requireNonNull(functionMetadata, "functionMetadata is null");
requireNonNull(functionBinding, "functionBinding is null");
}
}
}
