object: Support numerical search queries

Previously, protocol did not support numerical search queries for
objects. This may be needed for system attributes such as payload size
or creation epoch, and for user ones if required by the client
application.

New values of `MatchType` enumeration are added: '>', '>=', '<', "<=".
These attributes allow user to search for objects with any decimal
attributes. While only base-10 numbers are allowed, additional bases may
be supported in the future without new enumerations

Note that the previously added `STRING_EQUAL` / `STRING_NOT_EQUAL`
matchers are suitable for numerical '==' / '!='.

Closes #265.

Signed-off-by: Leonard Lyubich <leonard@morphbits.io>

object/service.proto

@@ -496,6 +496,9 @@ message SearchRequest {
     // objects. Most human users expect to get only object they can directly
     // work with. In that case, `$Object:ROOT` filter should be used.
     //
+    // If 'match_type' is numerical, both 'value' and object attribute MUST be
+    // base-10 numbers.
+    //
     // By default `key` field refers to the corresponding object's `Attribute`.
     // Some Object's header fields can also be accessed by adding `$Object:`
     // prefix to the name. Here is the list of fields available via this prefix:

object/types.proto

@@ -47,6 +47,18 @@ enum MatchType {
 
   // String prefix match
   COMMON_PREFIX = 4;
+
+  // Numerical 'greater than'
+  NUM_GT = 5;
+
+  // Numerical 'greater or equal than'
+  NUM_GE = 6;
+
+  // Numerical 'less than'
+  NUM_LT = 7;
+
+  // Numerical 'less or equal than'
+  NUM_LE = 8;
 }
 
 // Short header fields

proto-docs/object.md

@@ -771,6 +771,9 @@ container, including Regular object, Tombstones and Storage Group
 objects. Most human users expect to get only object they can directly
 work with. In that case, `$Object:ROOT` filter should be used.
 
+If 'match_type' is numerical, both 'value' and object attribute MUST be
+base-10 numbers.
+
 By default `key` field refers to the corresponding object's `Attribute`.
 Some Object's header fields can also be accessed by adding `$Object:`
 prefix to the name. Here is the list of fields available via this prefix:
@@ -1021,6 +1024,10 @@ Type of match expression
 | STRING_NOT_EQUAL | 2 | Full string mismatch |
 | NOT_PRESENT | 3 | Lack of key |
 | COMMON_PREFIX | 4 | String prefix match |
+| NUM_GT | 5 | Numerical 'greater than' |
+| NUM_GE | 6 | Numerical 'greater or equal than' |
+| NUM_LT | 7 | Numerical 'less than' |
+| NUM_LE | 8 | Numerical 'less or equal than' |