MDEV-398: Sergv related to spacial queries

- index_merge/intersection is unable to work on GIS indexes, because:
  1. index scans have no Rowid-Ordered-Retrieval property
  2. When one does an index-only read over a GIS index, they do not 
     get the index tuple, because index only contains bounding box of the geometry.
     This is why key_copy() call crashed.
This patch fixes #1, which makes the problem go away. Theoretically, it would 
be nice to check #2, too, but SE API semantics is not sufficiently precise to do it.

storage/maria/ha_maria.cc

@@ -914,6 +914,28 @@ const char *ha_maria::index_type(uint key_number)
 }
 
 
+ulong ha_maria::index_flags(uint inx, uint part, bool all_parts) const
+{
+  ulong flags;
+  if (table_share->key_info[inx].algorithm == HA_KEY_ALG_FULLTEXT)
+    flags= 0;
+  else 
+  if ((table_share->key_info[inx].flags & HA_SPATIAL ||
+      table_share->key_info[inx].algorithm == HA_KEY_ALG_RTREE))
+  {
+    /* All GIS scans are non-ROR scans. We also disable IndexConditionPushdown */
+    flags= HA_READ_NEXT | HA_READ_PREV | HA_READ_RANGE |
+           HA_READ_ORDER | HA_KEYREAD_ONLY | HA_KEY_SCAN_NOT_ROR;
+  }
+  else 
+  {
+    flags= HA_READ_NEXT | HA_READ_PREV | HA_READ_RANGE |
+          HA_READ_ORDER | HA_KEYREAD_ONLY | HA_DO_INDEX_COND_PUSHDOWN;
+  }
+  return flags;
+}
+
+
 double ha_maria::scan_time()
 {
   if (file->s->data_file_type == BLOCK_RECORD)

storage/maria/ha_maria.h

@@ -64,12 +64,7 @@ class ha_maria :public handler
   const char **bas_ext() const;
   ulonglong table_flags() const
   { return int_table_flags; }
-  ulong index_flags(uint inx, uint part, bool all_parts) const
-  {
-    return ((table_share->key_info[inx].algorithm == HA_KEY_ALG_FULLTEXT) ?
-            0 : HA_READ_NEXT | HA_READ_PREV | HA_READ_RANGE |
-            HA_READ_ORDER | HA_KEYREAD_ONLY | HA_DO_INDEX_COND_PUSHDOWN);
-  }
+  ulong index_flags(uint inx, uint part, bool all_parts) const;
   uint max_supported_keys() const
   { return MARIA_MAX_KEY; }
   uint max_supported_key_length() const;

storage/myisam/ha_myisam.cc

@@ -691,6 +691,28 @@ int ha_myisam::dump(THD* thd, int fd)
 #endif /* HAVE_REPLICATION */
 
 
+ulong ha_myisam::index_flags(uint inx, uint part, bool all_parts) const
+{
+  ulong flags;
+  if (table_share->key_info[inx].algorithm == HA_KEY_ALG_FULLTEXT)
+    flags= 0;
+  else 
+  if ((table_share->key_info[inx].flags & HA_SPATIAL ||
+      table_share->key_info[inx].algorithm == HA_KEY_ALG_RTREE))
+  {
+    /* All GIS scans are non-ROR scans. We also disable IndexConditionPushdown */
+    flags= HA_READ_NEXT | HA_READ_PREV | HA_READ_RANGE |
+           HA_READ_ORDER | HA_KEYREAD_ONLY | HA_KEY_SCAN_NOT_ROR;
+  }
+  else 
+  {
+    flags= HA_READ_NEXT | HA_READ_PREV | HA_READ_RANGE |
+          HA_READ_ORDER | HA_KEYREAD_ONLY | HA_DO_INDEX_COND_PUSHDOWN;
+  }
+  return flags;
+}
+
+
 /* Name is here without an extension */
 int ha_myisam::open(const char *name, int mode, uint test_if_locked)
 {

storage/myisam/ha_myisam.h

@@ -60,12 +60,7 @@ class ha_myisam: public handler
   int index_end();
   int rnd_end();
 
-  ulong index_flags(uint inx, uint part, bool all_parts) const
-  {
-    return ((table_share->key_info[inx].algorithm == HA_KEY_ALG_FULLTEXT) ?
-            0 : HA_READ_NEXT | HA_READ_PREV | HA_READ_RANGE |
-            HA_READ_ORDER | HA_KEYREAD_ONLY | HA_DO_INDEX_COND_PUSHDOWN);
-  }
+  ulong index_flags(uint inx, uint part, bool all_parts) const;
   uint max_supported_keys()          const { return MI_MAX_KEY; }
   uint max_supported_key_length()    const { return HA_MAX_KEY_LENGTH; }
   uint max_supported_key_part_length() const { return HA_MAX_KEY_LENGTH; }