EXPLAIN SELECT path,node_type,change_type,base_path,base_rev
FROM node_change WHERE rev=1
ORDER BY path;

SQLite with key
===============
CREATE TABLE node_change (
    rev text,
    path text,
    node_type text,
    change_type text,
    base_path text,
    base_rev text,
    UNIQUE (rev,path,change_type)
);
CREATE INDEX node_change_rev_idx ON node_change (rev);

addr  opcode          p1          p2          p3                               
----  --------------  ----------  ----------  ---------------------------------
0     Noop            0           0                                            
1     Goto            0           30                                           
2     Integer         0           0                                            
3     OpenRead        0           2                                            
4     SetNumColumns   0           6                                            
5     Integer         0           0                                            
6     OpenRead        2           3           keyinfo(3,BINARY,BINARY)         
7     Integer         1           0                                            
8     NotNull         -1          11                                           
9     Pop             1           0                                            
10    Goto            0           27                                           
11    MakeRecord      1           0           aaa                              
12    MemStore        0           0                                            
13    MoveGe          2           27                                           
14    MemLoad         0           0                                            
15    IdxGE           2           27          +                                
16    RowKey          2           0                                            
17    IdxIsNull       1           26                                           
18    IdxRowid        2           0                                            
19    MoveGe          0           0                                            
20    Column          0           1                                            
21    Column          0           2                                            
22    Column          0           3                                            
23    Column          0           4                                            
24    Column          0           5                                            
25    Callback        5           0                                            
26    Next            2           14                                           
27    Close           0           0                                            
28    Close           2           0                                            
29    Halt            0           0                                            
30    Transaction     0           0                                            
31    VerifyCookie    0           2                                            
32    Goto            0           2                                            
33    Noop            0           0                                            


SQLite without key
==================
CREATE TABLE node_change (
     rev text,
     path text,
     node_type text,
     change_type text,
     base_path text,
     base_rev text
);
CREATE INDEX node_change_rev_idx ON node_change (rev);

addr  opcode          p1          p2          p3                               
----  --------------  ----------  ----------  ---------------------------------
0     OpenVirtual     1           3           keyinfo(1,BINARY)                
1     Goto            0           49                                           
2     Integer         0           0                                            
3     OpenRead        0           2                                            
4     SetNumColumns   0           6                                            
5     Integer         0           0                                            
6     OpenRead        2           3           keyinfo(1,BINARY)                
7     Integer         1           0                                            
8     NotNull         -1          11                                           
9     Pop             1           0                                            
10    Goto            0           32                                           
11    MakeRecord      1           0           a                                
12    MemStore        0           0                                            
13    MoveGe          2           32                                           
14    MemLoad         0           0                                            
15    IdxGE           2           32          +                                
16    RowKey          2           0                                            
17    IdxIsNull       1           31                                           
18    IdxRowid        2           0                                            
19    MoveGe          0           0                                            
20    Column          0           1                                            
21    Column          0           2                                            
22    Column          0           3                                            
23    Column          0           4                                            
24    Column          0           5                                            
25    MakeRecord      5           0                                            
26    Column          0           1                                            
27    Sequence        1           0                                            
28    Pull            2           0                                            
29    MakeRecord      3           0                                            
30    IdxInsert       1           0                                            
31    Next            2           14                                           
32    Close           0           0                                            
33    Close           2           0                                            
34    OpenPseudo      3           0                                            
35    SetNumColumns   3           5                                            
36    Sort            1           47                                           
37    Integer         1           0                                            
38    Column          1           2                                            
39    Insert          3           0                                            
40    Column          3           0                                            
41    Column          3           1                                            
42    Column          3           2                                            
43    Column          3           3                                            
44    Column          3           4                                            
45    Callback        5           0                                            
46    Next            1           37                                           
47    Close           3           0                                            
48    Halt            0           0                                            
49    Transaction     0           0                                            
50    VerifyCookie    0           2                                            
51    Goto            0           2                                            
52    Noop            0           0                                            


PostgreSQL 8.1 with key
=======================
CREATE TABLE node_change (
    rev text,
    path text,
    node_type text,
    change_type text,
    base_path text,
    base_rev text,
    CONSTRAINT node_change_pk PRIMARY KEY (rev,path,change_type)
);
CREATE INDEX node_change_rev_idx ON node_change (rev);

 Index Scan using node_change_pk on node_change  (cost=0.00..8.30 rows=2 width=160)
   Index Cond: (rev = '1'::text)
(2 rows)


PostgreSQL 8.1 without key
==========================
CREATE TABLE node_change (
    rev text,
    path text,
    node_type text,
    change_type text,
    base_path text,
    base_rev text
);
CREATE INDEX node_change_rev_idx ON node_change (rev);

 Sort  (cost=8.31..8.31 rows=2 width=160)
   Sort Key: path
   ->  Index Scan using node_change_rev_idx on node_change  (cost=0.00..8.30 rows=2 width=160)
         Index Cond: (rev = '1'::text)
(4 rows)