xpath OPTIMIZE track child-only axis node moves

... which should guarantee that document order is
never broken so the sets do not have to be sorted.

Refs sysrepo/sysrepo#2843

Author: michalvasko

src/xpath.c

@@ -844,6 +844,7 @@ set_init(struct lyxp_set *new, const struct lyxp_set *set)
 {
     memset(new, 0, sizeof *new);
     if (set) {
+        new->non_child_axis = set->non_child_axis;
         new->ctx = set->ctx;
         new->cur_node = set->cur_node;
         new->root_type = set->root_type;
@@ -5613,6 +5614,7 @@ moveto_root(struct lyxp_set *set, uint32_t options)
         set->type = LYXP_SET_NODE_SET;
         set->used = 0;
         set_insert_node(set, NULL, 0, set->root_type, 0);
+        set->non_child_axis = 0;
     }
 
     return LY_SUCCESS;
@@ -6026,6 +6028,7 @@ moveto_node(struct lyxp_set *set, const struct lys_module *moveto_mod, const cha
             case LYXP_AXIS_PARENT:
             case LYXP_AXIS_PRECEDING:
             case LYXP_AXIS_PRECEDING_SIBLING:
+                result.non_child_axis = 1;
                 if (set_dup_node_check(&result, iter, iter_type, -1)) {
                     continue;
                 }
@@ -6050,8 +6053,12 @@ moveto_node(struct lyxp_set *set, const struct lys_module *moveto_mod, const cha
     *set = result;
     result.type = LYXP_SET_NUMBER;
 
-    /* sort the final set */
-    set_sort(set);
+    /* sort the final set if the document order could have been broken */
+    if (set->non_child_axis) {
+        set_sort(set);
+    } else {
+        assert(!set_sort(set));
+    }
 
 cleanup:
     lyxp_set_free_content(&result);
@@ -6756,6 +6763,7 @@ moveto_node_alldesc_child(struct lyxp_set *set, const struct lys_module *moveto_
     ret_set.ctx_size = set->ctx_size;
     lyxp_set_free_content(set);
     memcpy(set, &ret_set, sizeof *set);
+    assert(!set_sort(set));
 
     return LY_SUCCESS;
 }

src/xpath.h

@@ -3,7 +3,7 @@
  * @author Michal Vasko <[email protected]>
  * @brief YANG XPath evaluation functions header
  *
- * Copyright (c) 2015 - 2020 CESNET, z.s.p.o.
+ * Copyright (c) 2015 - 2022 CESNET, z.s.p.o.
  *
  * This source code is licensed under BSD 3-Clause License (the "License").
  * You may not use this file except in compliance with the License.
@@ -287,13 +287,14 @@ struct lyxp_set {
     } val;                              /**< Evaluated object (value). */
 
     /* this is valid only for type LYXP_SET_NODE_SET and LYXP_SET_SCNODE_SET */
-    uint32_t used;          /**< Number of nodes in the set. */
-    uint32_t size;          /**< Allocated size for the set. */
-    struct hash_table *ht;  /**< Hash table for quick determination of whether a node is in the set. */
+    uint32_t used;              /**< Number of nodes in the set. */
+    uint32_t size;              /**< Allocated size for the set. */
+    struct hash_table *ht;      /**< Hash table for quick determination of whether a node is in the set. */
 
     /* XPath context information, this is valid only for type LYXP_SET_NODE_SET */
-    uint32_t ctx_pos;       /**< Position of the current examined node in the set. */
-    uint32_t ctx_size;      /**< Position of the last node at the time the node was examined. */
+    uint32_t ctx_pos;           /**< Position of the current examined node in the set. */
+    uint32_t ctx_size;          /**< Position of the last node at the time the node was examined. */
+    ly_bool non_child_axis;     /**< Whether any node change was performed on a non-child axis. */
 
     /* general context */
     struct ly_ctx *ctx;                     /**< General context for logging. */