MDEV-24015: SQL Error (1038): Out of sort memory when enough memory for the sort buffer is provided

For a correlated subquery filesort is executed multiple times.
During each execution, sortlength() computed total sort key length in
Sort_keys::sort_length, without resetting it first.

Eventually Sort_keys::sort_length got larger than @@sort_buffer_size, which
caused filesort() to be aborted with error.

Fixed by making sortlength() to compute lengths only during the first
invocation. Subsequent invocations return pre-computed values.

mysql-test/main/order_by.result

@@ -4123,4 +4123,125 @@ f
 baz
 foo
 DROP TABLE t1;
+#
+# MDEV-24015: SQL Error (1038): Out of sort memory when enough memory for the
+# sort buffer is provided
+#
+CREATE TABLE t1 (a VARCHAR(100), b INT);
+CREATE TABLE t2 (a VARCHAR(100), b INT);
+INSERT INTO t1 SELECT 'abc', seq FROM seq_1_to_50;
+INSERT INTO t2 SELECT seq, seq FROM seq_1_to_50;
+set @save_sort_buffer_size= @@sort_buffer_size;
+set sort_buffer_size=2000;
+ANALYZE FORMAT=JSON
+SELECT (SELECT sum(t2.b) FROM t2 WHERE t1.b=t2.b GROUP BY t2.a) FROM t1;
+ANALYZE
+{
+  "query_block": {
+    "select_id": 1,
+    "r_loops": 1,
+    "r_total_time_ms": "REPLACED",
+    "table": {
+      "table_name": "t1",
+      "access_type": "ALL",
+      "r_loops": 1,
+      "rows": 50,
+      "r_rows": 50,
+      "r_table_time_ms": "REPLACED",
+      "r_other_time_ms": "REPLACED",
+      "filtered": 100,
+      "r_filtered": 100
+    },
+    "subqueries": [
+      {
+        "expression_cache": {
+          "r_loops": 50,
+          "r_hit_ratio": 0,
+          "query_block": {
+            "select_id": 2,
+            "r_loops": 50,
+            "r_total_time_ms": "REPLACED",
+            "filesort": {
+              "sort_key": "t2.a",
+              "r_loops": 50,
+              "r_total_time_ms": "REPLACED",
+              "r_used_priority_queue": false,
+              "r_output_rows": 1,
+              "r_buffer_size": "REPLACED" across executions)",
+              "r_sort_mode": "sort_key,rowid",
+              "temporary_table": {
+                "table": {
+                  "table_name": "t2",
+                  "access_type": "ALL",
+                  "r_loops": 50,
+                  "rows": 50,
+                  "r_rows": 50,
+                  "r_table_time_ms": "REPLACED",
+                  "r_other_time_ms": "REPLACED",
+                  "filtered": 100,
+                  "r_filtered": 2,
+                  "attached_condition": "t1.b = t2.b"
+                }
+              }
+            }
+          }
+        }
+      }
+    ]
+  }
+}
+SELECT (SELECT sum(t2.b) FROM t2 WHERE t1.b=t2.b GROUP BY t2.a) FROM t1;
+(SELECT sum(t2.b) FROM t2 WHERE t1.b=t2.b GROUP BY t2.a)
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+set sort_buffer_size= @save_sort_buffer_size;
+DROP TABLE t1,t2;
 # End of 10.5 tests

mysql-test/main/order_by.test

@@ -2556,4 +2556,24 @@ INSERT t1 VALUES ('foo','bar'),('baz','qux');
 SELECT COALESCE(a, b) AS f FROM t1 ORDER BY f;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-24015: SQL Error (1038): Out of sort memory when enough memory for the
+--echo # sort buffer is provided
+--echo #
+
+CREATE TABLE t1 (a VARCHAR(100), b INT);
+CREATE TABLE t2 (a VARCHAR(100), b INT);
+
+INSERT INTO t1 SELECT 'abc', seq FROM seq_1_to_50;
+INSERT INTO t2 SELECT seq, seq FROM seq_1_to_50;
+
+set @save_sort_buffer_size= @@sort_buffer_size;
+set sort_buffer_size=2000;
+--source include/analyze-format.inc
+ANALYZE FORMAT=JSON
+SELECT (SELECT sum(t2.b) FROM t2 WHERE t1.b=t2.b GROUP BY t2.a) FROM t1;
+SELECT (SELECT sum(t2.b) FROM t2 WHERE t1.b=t2.b GROUP BY t2.a) FROM t1;
+
+set sort_buffer_size= @save_sort_buffer_size;
+DROP TABLE t1,t2;
 --echo # End of 10.5 tests

sql/filesort.cc

@@ -2199,6 +2199,12 @@ sortlength(THD *thd, Sort_keys *sort_keys, bool *allow_packing_for_sortkeys)
   length=0;
   uint nullable_cols=0;
 
+  if (sort_keys->is_parameters_computed())
+  {
+    *allow_packing_for_sortkeys= sort_keys->using_packed_sortkeys();
+    return sort_keys->get_sort_length_with_memcmp_values();
+  }
+
   for (SORT_FIELD *sortorder= sort_keys->begin();
        sortorder != sort_keys->end();
        sortorder++)
@@ -2260,6 +2266,8 @@ sortlength(THD *thd, Sort_keys *sort_keys, bool *allow_packing_for_sortkeys)
   // add bytes for nullable_cols
   sort_keys->increment_original_sort_length(nullable_cols);
   *allow_packing_for_sortkeys= allow_packing_for_keys;
+  sort_keys->set_sort_length_with_memcmp_values(length + nullable_cols);
+  sort_keys->set_parameters_computed(true);
   DBUG_PRINT("info",("sort_length: %d",length));
   return length + nullable_cols;
 }
@@ -2518,7 +2526,7 @@ void Sort_param::try_to_pack_sortkeys()
     return;
 
   const uint sz= Sort_keys::size_of_length_field;
-  uint sort_len= sort_keys->get_sort_length();
+  uint sort_len= sort_keys->get_sort_length_with_original_values();
 
   /*
     Heuristic introduced, skip packing sort keys if saving less than 128 bytes

sql/sql_sort.h

@@ -255,10 +255,12 @@ class Sort_keys :public Sql_alloc,
 {
 public:
   Sort_keys(SORT_FIELD* arr, size_t count):
-  Sort_keys_array(arr, count),
-  m_using_packed_sortkeys(false),
-  size_of_packable_fields(0),
-  sort_length(0)
+    Sort_keys_array(arr, count),
+    m_using_packed_sortkeys(false),
+    size_of_packable_fields(0),
+    sort_length_with_original_values(0),
+    sort_length_with_memcmp_values(0),
+    parameters_computed(false)
   {
     DBUG_ASSERT(!is_null());
   }
@@ -280,14 +282,24 @@ public:
     return size_of_packable_fields;
   }
 
-  void set_sort_length(uint len)
+  void set_sort_length_with_original_values(uint len)
   {
-    sort_length= len;
+    sort_length_with_original_values= len;
   }
 
-  uint get_sort_length()
+  uint get_sort_length_with_original_values()
   {
-    return sort_length;
+    return sort_length_with_original_values;
+  }
+
+  void set_sort_length_with_memcmp_values(uint len)
+  {
+    sort_length_with_memcmp_values= len;
+  }
+
+  uint get_sort_length_with_memcmp_values()
+  {
+    return sort_length_with_memcmp_values;
   }
 
   static void store_sortkey_length(uchar *p, uint sz)
@@ -307,9 +319,12 @@ public:
 
   void increment_original_sort_length(uint len)
   {
-    sort_length+= len;
+    sort_length_with_original_values+= len;
   }
 
+  bool is_parameters_computed() { return parameters_computed; }
+  void set_parameters_computed(bool val) { parameters_computed= val; }
+
   static const uint size_of_length_field= 4;
 
 private:
@@ -317,10 +332,21 @@ private:
   uint size_of_packable_fields;     // Total length bytes for packable columns
 
   /*
-    The length that would be needed if we stored non-packed mem-comparable
-    images of fields?
+    The sort length for all the keyparts storing the original values
   */
-  uint sort_length;
+  uint sort_length_with_original_values;
+
+  /*
+    The sort length for all the keyparts storing the mem-comparable images
+  */
+  uint sort_length_with_memcmp_values;
+
+  /*
+    TRUE       parameters(like sort_length_* , size_of_packable_field)
+               are computed
+    FALSE      otherwise.
+  */
+  bool parameters_computed;
 };