This patch complements the patch for mdev-10855.

It allows to push conditions into derived with window functions not
only in the cases when the window specifications of these window
functions use the same partition, but also in the cases when the window
functions use partitions that share only some fields. In these
cases only the conditions over the common fields are pushed.

mysql-test/r/derived_cond_pushdown.result

@@ -9243,6 +9243,242 @@ EXPLAIN
     }
   }
 }
+set statement optimizer_switch='condition_pushdown_for_derived=off' for select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a,c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+a	c	sum_b	avg_b
+7	cc	28	14.0000
+7	cc	28	14.0000
+3	aa	92	46.0000
+7	bb	126	42.0000
+4	aa	15	15.0000
+7	bb	126	42.0000
+7	bb	126	42.0000
+3	bb	40	40.0000
+3	aa	92	46.0000
+select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a,c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+a	c	sum_b	avg_b
+7	cc	28	14.0000
+7	cc	28	14.0000
+3	aa	92	46.0000
+7	bb	126	42.0000
+4	aa	15	15.0000
+7	bb	126	42.0000
+7	bb	126	42.0000
+3	bb	40	40.0000
+3	aa	92	46.0000
+explain select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a,c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	16	Using where
+2	DERIVED	t2	ALL	idx	NULL	NULL	NULL	20	Using where; Using temporary
+explain format=json select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a,c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "<derived2>",
+      "access_type": "ALL",
+      "rows": 16,
+      "filtered": 100,
+      "attached_condition": "t.a > 2 and t.c in ('aa','bb','cc')",
+      "materialized": {
+        "query_block": {
+          "select_id": 2,
+          "window_functions_computation": {
+            "sorts": {
+              "filesort": {
+                "sort_key": "t2.a, t2.c"
+              }
+            },
+            "temporary_table": {
+              "table": {
+                "table_name": "t2",
+                "access_type": "ALL",
+                "possible_keys": ["idx"],
+                "rows": 20,
+                "filtered": 80,
+                "attached_condition": "t2.a > 2 and t2.c in ('aa','bb','cc')"
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
+set statement optimizer_switch='condition_pushdown_for_derived=off' for select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+a	c	sum_b	avg_b
+7	cc	28	30.8000
+7	cc	28	30.8000
+3	aa	92	44.0000
+7	bb	126	30.8000
+4	aa	15	46.3333
+7	bb	126	30.8000
+7	bb	126	30.8000
+3	bb	40	44.0000
+3	aa	92	44.0000
+select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+a	c	sum_b	avg_b
+7	cc	28	30.8000
+7	cc	28	30.8000
+3	aa	92	44.0000
+7	bb	126	30.8000
+4	aa	15	46.3333
+7	bb	126	30.8000
+7	bb	126	30.8000
+3	bb	40	44.0000
+3	aa	92	44.0000
+explain select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	16	Using where
+2	DERIVED	t2	ALL	idx	NULL	NULL	NULL	20	Using where; Using temporary
+explain format=json select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by a) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "<derived2>",
+      "access_type": "ALL",
+      "rows": 16,
+      "filtered": 100,
+      "attached_condition": "t.a > 2 and t.c in ('aa','bb','cc')",
+      "materialized": {
+        "query_block": {
+          "select_id": 2,
+          "window_functions_computation": {
+            "sorts": {
+              "filesort": {
+                "sort_key": "t2.a, t2.c"
+              }
+            },
+            "temporary_table": {
+              "table": {
+                "table_name": "t2",
+                "access_type": "ALL",
+                "possible_keys": ["idx"],
+                "rows": 20,
+                "filtered": 80,
+                "attached_condition": "t2.a > 2"
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
+set statement optimizer_switch='condition_pushdown_for_derived=off' for select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+a	c	sum_b	avg_b
+7	cc	28	14.0000
+7	cc	28	14.0000
+3	aa	92	35.4000
+7	bb	126	36.5000
+4	aa	15	35.4000
+7	bb	126	36.5000
+7	bb	126	36.5000
+3	bb	40	36.5000
+3	aa	92	35.4000
+select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+a	c	sum_b	avg_b
+7	cc	28	14.0000
+7	cc	28	14.0000
+3	aa	92	35.4000
+7	bb	126	36.5000
+4	aa	15	35.4000
+7	bb	126	36.5000
+7	bb	126	36.5000
+3	bb	40	36.5000
+3	aa	92	35.4000
+explain select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	20	Using where
+2	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	20	Using where; Using temporary
+explain format=json select * from (select a, c,
+sum(b) over (partition by a,c) as sum_b,
+avg(b) over (partition by c) as avg_b
+from t2 ) as t
+where t.a > 2 and t.c in ('aa','bb','cc');
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "<derived2>",
+      "access_type": "ALL",
+      "rows": 20,
+      "filtered": 100,
+      "attached_condition": "t.a > 2 and t.c in ('aa','bb','cc')",
+      "materialized": {
+        "query_block": {
+          "select_id": 2,
+          "window_functions_computation": {
+            "sorts": {
+              "filesort": {
+                "sort_key": "t2.c"
+              },
+              "filesort": {
+                "sort_key": "t2.a, t2.c"
+              }
+            },
+            "temporary_table": {
+              "table": {
+                "table_name": "t2",
+                "access_type": "ALL",
+                "rows": 20,
+                "filtered": 100,
+                "attached_condition": "t2.c in ('aa','bb','cc')"
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
 drop table t1,t2;
 set optimizer_switch= @save_optimizer_switch;
 #

mysql-test/t/derived_cond_pushdown.test

@@ -1617,6 +1617,42 @@ eval $q4;
 eval explain $q4;
 eval explain format=json $q4;
 
+let $q5=
+select * from (select a, c,
+                      sum(b) over (partition by a,c) as sum_b,
+                      avg(b) over (partition by a,c) as avg_b
+               from t2 ) as t
+  where t.a > 2 and t.c in ('aa','bb','cc');
+
+eval $no_pushdown $q5;
+eval $q5;
+eval explain $q5;
+eval explain format=json $q5;
+
+let $q6=
+select * from (select a, c,
+                      sum(b) over (partition by a,c) as sum_b,
+                      avg(b) over (partition by a) as avg_b
+               from t2 ) as t
+  where t.a > 2 and t.c in ('aa','bb','cc');
+
+eval $no_pushdown $q6;
+eval $q6;
+eval explain $q6;
+eval explain format=json $q6;
+
+let $q7=
+select * from (select a, c,
+                      sum(b) over (partition by a,c) as sum_b,
+                      avg(b) over (partition by c) as avg_b
+               from t2 ) as t
+  where t.a > 2 and t.c in ('aa','bb','cc');
+
+eval $no_pushdown $q7;
+eval $q7;
+eval explain $q7;
+eval explain format=json $q7;
+
 drop table t1,t2;
 
 set optimizer_switch= @save_optimizer_switch;

sql/sql_derived.cc

@@ -1251,8 +1251,9 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived)
     {
       if (sl->join->group_list || sl->join->implicit_grouping)
         continue;
-      if (!(sl->window_specs.elements == 1 &&
-            sl->window_specs.head()->partition_list))
+      ORDER *common_partition_fields= 
+	       sl->find_common_window_func_partition_fields(thd);           
+      if (!common_partition_fields)
         continue;
       extracted_cond_copy= !sl->next_select() ?
                            extracted_cond :
@@ -1260,9 +1261,8 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived)
       if (!extracted_cond_copy)
         continue;
 
-      Item *cond_over_partition_fields;
-      ORDER *grouping_list= sl->window_specs.head()->partition_list->first; 
-      sl->collect_grouping_fields(thd, grouping_list);
+      Item *cond_over_partition_fields;; 
+      sl->collect_grouping_fields(thd, common_partition_fields);
       sl->check_cond_extraction_for_grouping_fields(extracted_cond_copy,
                                                     derived);
       cond_over_partition_fields=

sql/sql_lex.h

@@ -1246,6 +1246,7 @@ class st_select_lex: public st_select_lex_node
   }
 
   bool have_window_funcs() const { return (window_funcs.elements !=0); }
+  ORDER *find_common_window_func_partition_fields(THD *thd);
 
   bool cond_pushdown_is_allowed() const
   { return !olap && !explicit_limit; }

sql/sql_window.cc

+#include "sql_parse.h"
 #include "sql_select.h"
 #include "sql_list.h"
 #include "item_windowfunc.h"
@@ -307,6 +308,83 @@ setup_windows(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
   DBUG_RETURN(0);
 }
 
+
+/**
+  @brief
+  Find fields common for all partition lists used in window functions
+
+  @param thd       The thread handle
+
+  @details
+   This function looks for the field references in the partition lists
+   of all window functions used in this select that are common for
+   all the partition lists. The function returns an ORDER list contained
+   all such references.The list either is specially built by the function
+   or is taken directly from the first window specification.
+
+  @retval
+    pointer to the first element of the ORDER list contained field
+    references common for all partition lists
+    0 if no such reference is found.
+*/
+
+ORDER *st_select_lex::find_common_window_func_partition_fields(THD *thd)
+{
+  ORDER *ord;
+  Item *item;
+  DBUG_ASSERT(window_funcs.elements);
+  List_iterator_fast<Item_window_func> it(window_funcs);
+  Item_window_func *wf= it++;
+  if (!wf->window_spec->partition_list)
+    return 0;
+  List<Item> common_fields;
+  uint first_partition_elements;
+  for (ord= wf->window_spec->partition_list->first; ord; ord= ord->next)
+  {
+    if ((*ord->item)->real_item()->type() == Item::FIELD_ITEM)
+      common_fields.push_back(*ord->item, thd->mem_root);
+    first_partition_elements++;
+  }
+  if (window_specs.elements == 1 &&
+      common_fields.elements == first_partition_elements)
+    return wf->window_spec->partition_list->first;
+  List_iterator<Item> li(common_fields);
+  while (common_fields.elements && (wf= it++))
+  {
+    if (!wf->window_spec->partition_list)
+      return 0;
+    while ((item= li++))
+    {
+      for (ord= wf->window_spec->partition_list->first; ord; ord= ord->next)
+      {
+        if (item->eq(*ord->item, false))
+	  break;
+      }
+      if (!ord)
+        li.remove();
+    }
+    li.rewind();
+  }
+  if (!common_fields.elements)
+    return 0;
+  if (common_fields.elements == first_partition_elements)
+    return wf->window_spec->partition_list->first;
+  SQL_I_List<ORDER> res_list;
+  it.rewind();
+  wf= it++;
+  for (ord= wf->window_spec->partition_list->first, item= li++;
+       ord; ord= ord->next)
+  {
+    if (item != *ord->item)
+      continue;
+    if (add_to_list(thd, res_list, item, ord->direction))
+      return 0;
+    item= li++;
+  }
+  return res_list.first;
+}
+
+
 /////////////////////////////////////////////////////////////////////////////
 // Sorting window functions to minimize the number of table scans
 // performed during the computation of these functions