analyse GREATEST and LEAST functions

Author: schlndh

src/Database/FunctionInfo/FunctionInfoRegistryFactory.php

@@ -27,8 +27,9 @@ public function createDefaultFunctionInfos(): array
 			new DateAddSub(),
 			new DateFormat(),
 			new FoundRows(),
-			new IfFunction(),
+			new GreatestLeast(),
 			new GroupConcat(),
+			new IfFunction(),
 			new LowerUpper(),
 			new MaxMin(),
 			new Now(),

src/Database/FunctionInfo/GreatestLeast.php

@@ -0,0 +1,125 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MariaStan\Database\FunctionInfo;
+
+use MariaStan\Analyser\AnalyserConditionTypeEnum;
+use MariaStan\Analyser\ExprTypeResult;
+use MariaStan\Ast\Expr\FunctionCall\FunctionCall;
+use MariaStan\Parser\Exception\ParserException;
+use MariaStan\Schema\DbType\DateTimeType;
+use MariaStan\Schema\DbType\DbType;
+use MariaStan\Schema\DbType\DbTypeEnum;
+use MariaStan\Schema\DbType\FloatType;
+use MariaStan\Schema\DbType\NullType;
+
+use function array_fill;
+use function count;
+
+final class GreatestLeast implements FunctionInfo
+{
+	/** @inheritDoc */
+	public function getSupportedFunctionNames(): array
+	{
+		return ['GREATEST', 'LEAST'];
+	}
+
+	public function getFunctionType(): FunctionTypeEnum
+	{
+		return FunctionTypeEnum::SIMPLE;
+	}
+
+	public function checkSyntaxErrors(FunctionCall $functionCall): void
+	{
+		$args = $functionCall->getArguments();
+		$argCount = count($args);
+
+		if ($argCount >= 2) {
+			return;
+		}
+
+		throw new ParserException(
+			FunctionInfoHelper::createArgumentCountErrorMessageMin(
+				$functionCall->getFunctionName(),
+				2,
+				$argCount,
+			),
+		);
+	}
+
+	/** @inheritDoc */
+	public function getInnerConditions(?AnalyserConditionTypeEnum $condition, array $arguments): array
+	{
+		// TRUTHY(LEAST(A, ...)) => NOT_NULL(A, ...)
+		// FALSY(LEAST(A, ...)) => NOT_NULL(A, ...)
+		// NOT_NULL(LEAST(A, ...)) => NOT_NULL(A, ...)
+		// NULL(LEAST(A, ...)) => NULL(A) || NULL(...)
+		$innerCondition = match ($condition) {
+			null, AnalyserConditionTypeEnum::NULL => $condition,
+			// TODO: Change it to NOT_NULL after 10.11.8 https://jira.mariadb.org/browse/MDEV-21034
+			AnalyserConditionTypeEnum::TRUTHY => null,
+			default => AnalyserConditionTypeEnum::NOT_NULL,
+		};
+
+		return array_fill(0, count($arguments), $innerCondition);
+	}
+
+	/**
+	 * @inheritDoc
+	 * @phpcsSuppress SlevomatCodingStandard.Functions.UnusedParameter
+	 */
+	public function getReturnType(
+		FunctionCall $functionCall,
+		array $argumentTypes,
+		?AnalyserConditionTypeEnum $condition,
+		bool $isNonEmptyAggResultSet,
+	): ExprTypeResult {
+		$leftType = $argumentTypes[0]->type;
+		$isNullable = $argumentTypes[0]->isNullable;
+		$knowledgeBase = $argumentTypes[0]->knowledgeBase;
+		$i = 1;
+		$argCount = count($argumentTypes);
+
+		while ($i < $argCount) {
+			$rightKnowledgeBase = $argumentTypes[$i]->knowledgeBase;
+			$rightType = $argumentTypes[$i]->type;
+			$isNullable = $isNullable || $argumentTypes[$i]->isNullable;
+			$i++;
+			$leftType = self::castToCommonType($leftType, $rightType);
+			$knowledgeBase = $rightKnowledgeBase === null
+				? null
+				: match ($condition) {
+					null => null,
+					AnalyserConditionTypeEnum::NULL => $knowledgeBase?->or($rightKnowledgeBase),
+					default => $knowledgeBase?->and($rightKnowledgeBase),
+				};
+		}
+
+		return new ExprTypeResult($leftType, $isNullable, null, $knowledgeBase);
+	}
+
+	private static function castToCommonType(DbType $leftType, DbType $rightType): DbType
+	{
+		$lt = $leftType::getTypeEnum();
+		$rt = $rightType::getTypeEnum();
+		$typesInvolved = [
+			$lt->value => 1,
+			$rt->value => 1,
+		];
+
+		if (isset($typesInvolved[DbTypeEnum::NULL->value])) {
+			return new NullType();
+		}
+
+		if (isset($typesInvolved[DbTypeEnum::DATETIME->value])) {
+			return new DateTimeType();
+		}
+
+		if (isset($typesInvolved[DbTypeEnum::VARCHAR->value]) && count($typesInvolved) === 2) {
+			return new FloatType();
+		}
+
+		return FunctionInfoHelper::castToCommonType($leftType, $rightType);
+	}
+}

tests/Analyser/AnalyserTest.php

@@ -988,6 +988,8 @@ private static function provideValidFunctionCallTestData(): iterable
 				$selects["COALESCE({$label1}, {$label2}, int)"] = "SELECT COALESCE(NULL, {$value1}, {$value2}, 9)";
 				$selects["ROUND({$label1}, {$label2})"] = "SELECT ROUND({$value1}, {$value2})";
 				$selects["CONCAT({$label1}, {$label2})"] = "SELECT CONCAT({$value1}, {$value2})";
+				$selects["LEAST({$label1}, {$label2})"] = "SELECT LEAST({$value1}, {$value2})";
+				$selects["GREATEST({$label1}, {$label2})"] = "SELECT GREATEST({$value1}, {$value2})";
 			}
 
 			$selects["TRIM({$label1})"] = "SELECT TRIM({$value1})";
@@ -1002,6 +1004,8 @@ private static function provideValidFunctionCallTestData(): iterable
 			$selects["UPPER({$label1})"] = "SELECT UPPER({$value1})";
 			$selects["UCASE({$label1})"] = "SELECT UCASE({$value1})";
 			$selects["ABS({$label1})"] = "SELECT ABS({$value1})";
+			$selects["LEAST({$label1}, {$label1}, {$label1})"] = "SELECT LEAST({$value1}, {$value1}, {$value1})";
+			$selects["GREATEST({$label1}, {$label1}, {$label1})"] = "SELECT GREATEST({$value1}, {$value1}, {$value1})";
 		}
 
 		// TODO: figure out the context in which the function is called and adjust the return type accordingly.
@@ -1735,6 +1739,11 @@ private static function provideValidNullabilityOperatorTestData(): iterable
 			'ABS(col_int) IS NOT NULL',
 			'ABS(col_int)',
 			'NOT ABS(col_int)',
+			'LEAST(col_int, col_vchar) IS NOT NULL',
+			// TODO: Enable this after 10.11.8. https://jira.mariadb.org/browse/MDEV-21034
+			//'LEAST(col_int, col_vchar)',
+			'NOT LEAST(col_int, col_vchar)',
+			'GREATEST(col_int, col_vchar) IS NULL',
 		];
 
 		foreach (['COALESCE', 'IFNULL', 'NVL'] as $coalesceFn) {