Index: src/wp-includes/link-template.php
===================================================================
--- src/wp-includes/link-template.php	(revision 27562)
+++ src/wp-includes/link-template.php	(working copy)
@@ -1273,7 +1273,7 @@
 	 * @return mixed Post object on success. False if no adjacent post exists. Null on failure.
 	 */
 	protected function get_post( $args ) {
-		$this->current_post = get_post( $args['post'] );
+		$this->current_post   = get_post( $args['post'] );
 		$this->excluded_terms = array_map( 'intval', $args['excluded_terms'] );
 		$this->adjacent       = $args['previous'] ? 'previous' : 'next';
 		$this->taxonomy       = $args['taxonomy'];
@@ -1291,14 +1291,20 @@
 
 		// Build our arguments for WP_Query.
 		$query_args = array(
-			'posts_per_page'   => 1,
-			'post_status'      => 'publish',
-			'post_type'        => 'post',
-			'orderby'          => 'date',
-			'order'            => 'previous' === $this->adjacent ? 'DESC' : 'ASC',
-			'no_found_rows'    => true,
-			'cache_results'    => true,
-			'date_query'       => array(),
+			'posts_per_page'      => 1,
+			'post_status'         => 'publish',
+			'post_type'           => 'post',
+			'orderby'             => 'date',
+			'order'               => 'previous' === $this->adjacent ? 'DESC' : 'ASC',
+			'ignore_sticky_posts' => true,
+			'date_query'          => array(),
+
+			// Performance considerations:
+			'no_found_rows'          => true,
+			'cache_results'          => true,
+			'update_post_term_cache' => false,
+			'update_post_meta_cache' => false,
+			'split_the_query'        => wp_using_ext_object_cache(),
 		);
 
 		$tax_query = array();
@@ -1388,6 +1394,11 @@
 		 */
 		remove_filter( 'posts_clauses', array( $this, 'filter' ) );
 
+		/**
+		 * Posts table must be aliased as `p` for backwards compatibility with query previously generated by `get_adjacent_post()`.
+		 */
+		$clauses = array_map( array( $this, 'alias_posts_table' ), $clauses );
+
 		/*
 		 * The `join` and `where` filters are identical in their parameters,
 		 * so we can use the same approach for both.
@@ -1398,6 +1409,12 @@
 			}
 		}
 
+		/**
+		 * Posts table must be aliased as `p` for backwards compatibility with query previously generated by `get_adjacent_post()`.
+		 * No filter on the table name exists, so we have to leverage the next applied filter, that for the join clause.
+		 */
+		$clauses['join'] = 'AS p ' . $clauses['join'];
+
 		/*
 		 * The legacy `sort` filter combined the ORDER BY and LIMIT clauses,
 		 * while `WP_Query` does not, which requires special handling.
@@ -1411,6 +1428,19 @@
 	}
 
 	/**
+	 * Alias posts table as `p` to match query previously built by `get_adjacent_post()`
+	 *
+	 * @global $wpdb
+	 * @param string  Clause to alias
+	 * @return string
+	 */
+	protected function alias_posts_table( $clause ) {
+		global $wpdb;
+
+		return str_replace( $wpdb->posts, 'p', $clause );
+	}
+
+	/**
 	 * Apply the deprecated `join` or `where` clause filter to the clauses built by WP_Query.
 	 *
 	 * @param string $value
Index: src/wp-includes/load.php
===================================================================
--- src/wp-includes/load.php	(revision 27562)
+++ src/wp-includes/load.php	(working copy)
@@ -377,7 +377,7 @@
 	$current_using = $_wp_using_ext_object_cache;
 	if ( null !== $using )
 		$_wp_using_ext_object_cache = $using;
-	return $current_using;
+	return (bool) $current_using;
 }
 
 /**
Index: src/wp-includes/query.php
===================================================================
--- src/wp-includes/query.php	(revision 27562)
+++ src/wp-includes/query.php	(working copy)
@@ -3221,6 +3221,9 @@
 		}
 
 		$split_the_query = ( $old_request == $this->request && "$wpdb->posts.*" == $fields && !empty( $limits ) && $q['posts_per_page'] < 500 );
+		if ( $split_the_query && isset( $q['split_the_query'] ) && empty( $q['split_the_query'] ) ) {
+			$split_the_query = false;
+		}
 
 		/**
 		 * Filter whether to split the query.
Index: tests/phpunit/tests/link.php
===================================================================
--- tests/phpunit/tests/link.php	(revision 27562)
+++ tests/phpunit/tests/link.php	(working copy)
@@ -251,7 +251,7 @@
 	function filter_next_post_join( $join ) {
 		global $wpdb;
 
-		$join .= " INNER JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID = {$wpdb->postmeta}.post_id";
+		$join .= " INNER JOIN {$wpdb->postmeta} ON p.ID = {$wpdb->postmeta}.post_id";
 		return $join;
 	}
 
@@ -269,10 +269,7 @@
 	 * Filter callback for `test_legacy_get_adjacent_post_filters()`
 	 */
 	function filter_next_post_sort( $sort ) {
-		global $wpdb;
-
-		$sort = str_replace( $wpdb->posts . '.post_date', $wpdb->posts . '.post_title', $sort );
-		return $sort;
+		return str_replace( 'p.post_date', 'p.post_title', $sort );
 	}
 
 	/**