SELECT COUNT(*) FROM A1;
6066915 -- всего записей

SELECT COUNT(*) FROM A2 WHERE H_ID >= 1065093
206 -- записей по фильтру

CREATE VIEW V_A1 AS
    SELECT A1_ID,  H.H_NUM,    NVL(A.H_ID, H.H_ID) H_ID,   A.STEP,    A.P_ID,    A.RECTIME,    ENAME,      ANL,     SMPLNO
FROM A2 H
LEFT OUTER JOIN A1 A ON H.H_ID = A.H_ID;

explain plan FOR SELECT * FROM V_A1 WHERE H_ID >= 1065093;
select * from table(dbms_xplan.display);

Plan hash value: 238673394

Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - filter(NVL("A"."H_ID","H"."H_ID")>=1065093)
   4 - access("H"."H_ID"="A"."H_ID"(+))
 
Note
-----
   - dynamic sampling used for this statement (level=4)

explain plan FOR 
SELECT A1_ID,  H.H_NUM,    NVL(A.H_ID, H.H_ID) H_ID,   A.STEP,    A.P_ID,    A.RECTIME,    ENAME,      ANL,     SMPLNO
    FROM A2 H
    LEFT OUTER JOIN A1 A ON H.H_ID = A.H_ID
WHERE H.H_ID >= 1065093;
select * from table(dbms_xplan.display);

Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("H"."H_ID">=1065093)
   5 - access("H"."H_ID"="A"."H_ID"(+))
       filter("A"."H_ID"(+)>=1065093)
 
Note
-----
   - dynamic sampling used for this statement (level=4)

CREATE VIEW V_A1 AS
    SELECT A1_ID,  H.H_NUM,    /* NVL(A.H_ID, H.H_ID) ->*/ H.H_ID,   A.STEP,    A.P_ID,    A.RECTIME,    ENAME,      ANL,     SMPLNO
FROM A2 H
LEFT OUTER JOIN A1 A ON H.H_ID = A.H_ID;

explain plan FOR SELECT * FROM V_A1 WHERE H_ID >= 1065093;
select * from table(dbms_xplan.display);
Plan hash value: 2181453333

| Id  | Operation                    | Name                  | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                       |    14 |  2002 |    66   (0)| 00:00:01 |
|   1 |  NESTED LOOPS OUTER          |                       |    14 |  2002 |    66   (0)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| A2                    |     1 |    10 |     3   (0)| 00:00:01 |
|*  3 |    INDEX RANGE SCAN          | PK_A2_H_ID            |     1 |       |     2   (0)| 00:00:01 |
|   4 |   TABLE ACCESS BY INDEX ROWID| A1                    |    14 |  1862 |    63   (0)| 00:00:01 |
|*  5 |    INDEX RANGE SCAN          | IDX_A1_H_ID           |  1433 |       |     2   (0)| 00:00:01 |