Add lsm3_top_index_size function

Author: knizhnik

lsm3--1.0.sql

@@ -797,3 +797,7 @@ AS 'MODULE_PATHNAME' LANGUAGE C STRICT PARALLEL RESTRICTED;
 -- Wait merge completion
 CREATE FUNCTION lsm3_wait_merge_completion(index regclass) returns void
 AS 'MODULE_PATHNAME' LANGUAGE C STRICT PARALLEL RESTRICTED;
+
+-- Get active top index size (number of blocks)
+CREATE FUNCTION lsm3_top_index_size(index regclass) returns void
+AS 'MODULE_PATHNAME' LANGUAGE C STRICT PARALLEL RESTRICTED;

lsm3.c

@@ -39,6 +39,7 @@ PG_FUNCTION_INFO_V1(lsm3_btree_wrapper);
 PG_FUNCTION_INFO_V1(lsm3_get_merge_count);
 PG_FUNCTION_INFO_V1(lsm3_start_merge);
 PG_FUNCTION_INFO_V1(lsm3_wait_merge_completion);
+PG_FUNCTION_INFO_V1(lsm3_top_index_size);
 
 extern void	_PG_init(void);
 extern void	_PG_fini(void);
@@ -1007,3 +1008,13 @@ lsm3_wait_merge_completion(PG_FUNCTION_ARGS)
 	}
 	PG_RETURN_NULL();
 }
+
+Datum
+lsm3_top_index_size(PG_FUNCTION_ARGS)
+{
+	Oid	relid = PG_GETARG_OID(0);
+	Relation index = index_open(relid, AccessShareLock);
+	Lsm3DictEntry* entry = lsm3_get_entry(index);
+	index_close(index, AccessShareLock);
+	PG_RETURN_INT32(lsm3_get_index_size(lsm3_get_index_size(entry->top[entry->active_index])));
+}