Add a method to compare empty strings with an expression

Signed-off-by: Joas Schilling <coding@schilljs.com>

lib/private/DB/QueryBuilder/ExpressionBuilder/ExpressionBuilder.php

@@ -31,6 +31,7 @@ use OC\DB\QueryBuilder\QueryFunction;
 use OC\DB\QueryBuilder\QuoteHelper;
 use OCP\DB\QueryBuilder\IExpressionBuilder;
 use OCP\DB\QueryBuilder\ILiteral;
+use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\DB\QueryBuilder\IQueryFunction;
 use OCP\IDBConnection;
 
@@ -350,6 +351,28 @@ class ExpressionBuilder implements IExpressionBuilder {
 		return $this->expressionBuilder->notIn($x, $y);
 	}
 
+	/**
+	 * Creates a $x = '' statement, because Oracle needs a different check
+	 *
+	 * @param string $x The field in string format to be inspected by the comparison.
+	 * @return string
+	 * @since 13.0.0
+	 */
+	public function emptyString($x) {
+		return $this->eq($x, $this->literal('', IQueryBuilder::PARAM_STR));
+	}
+
+	/**
+	 * Creates a `$x <> ''` statement, because Oracle needs a different check
+	 *
+	 * @param string $x The field in string format to be inspected by the comparison.
+	 * @return string
+	 * @since 13.0.0
+	 */
+	public function nonEmptyString($x) {
+		return $this->neq($x, $this->literal('', IQueryBuilder::PARAM_STR));
+	}
+
 	/**
 	 * Binary AND Operator copies a bit to the result if it exists in both operands.
 	 *

lib/private/DB/QueryBuilder/ExpressionBuilder/OCIExpressionBuilder.php

@@ -137,6 +137,28 @@ class OCIExpressionBuilder extends ExpressionBuilder {
 		return $this->expressionBuilder->notIn($x, $y);
 	}
 
+	/**
+	 * Creates a $x = '' statement, because Oracle needs a different check
+	 *
+	 * @param string $x The field in string format to be inspected by the comparison.
+	 * @return string
+	 * @since 13.0.0
+	 */
+	public function emptyString($x) {
+		return $this->isNull($x);
+	}
+
+	/**
+	 * Creates a `$x <> ''` statement, because Oracle needs a different check
+	 *
+	 * @param string $x The field in string format to be inspected by the comparison.
+	 * @return string
+	 * @since 13.0.0
+	 */
+	public function nonEmptyString($x) {
+		return $this->isNotNull($x);
+	}
+
 	/**
 	 * Returns a IQueryFunction that casts the column to the given type
 	 *

lib/private/Repair/NC13/RepairInvalidPaths.php

@@ -70,7 +70,7 @@ class RepairInvalidPaths implements IRepairStep {
 			->from('filecache', 'f')
 			->innerJoin('f', 'filecache', 'p', $builder->expr()->andX(
 				$builder->expr()->eq('f.parent', 'p.fileid'),
-				$builder->expr()->isNotNull('p.name')
+				$builder->expr()->nonEmptyString('p.name')
 			))
 			->where($builder->expr()->neq('f.path', $computedPath))
 			->setMaxResults(self::MAX_ROWS);

lib/public/DB/QueryBuilder/IExpressionBuilder.php

@@ -305,6 +305,24 @@ interface IExpressionBuilder {
 	 */
 	public function notIn($x, $y, $type = null);
 
+	/**
+	 * Creates a $x = '' statement, because Oracle needs a different check
+	 *
+	 * @param string $x The field in string format to be inspected by the comparison.
+	 * @return string
+	 * @since 13.0.0
+	 */
+	public function emptyString($x);
+
+	/**
+	 * Creates a `$x <> ''` statement, because Oracle needs a different check
+	 *
+	 * @param string $x The field in string format to be inspected by the comparison.
+	 * @return string
+	 * @since 13.0.0
+	 */
+	public function nonEmptyString($x);
+
 
 	/**
 	 * Creates a bitwise AND comparison