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aa6e2d853a
## Main stuff - Support iterating an index backwards - Support scanning an index (instead of seeking with a condition) - Support backwards index seeks - Support backwards rowid seeks - Fix existing backwards iteration logic for table btrees - Remove ORDER BY entirely if any index satisfies the ordering - Add fuzz tests for rowid seeks, 1 and 2 column index seeks ## Bytecode examples (note the lack of order by sorting): one column index order by, forwards: ```sql limbo> explain select first_name from users order by age; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 13 0 0 Start at 13 1 OpenReadAsync 0 2 0 0 table=users, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 274 0 0 table=age_idx, root=274 4 OpenReadAwait 0 0 0 0 5 RewindAsync 1 0 0 0 6 RewindAwait 1 12 0 0 Rewind table age_idx 7 DeferredSeek 1 0 0 0 8 Column 0 1 1 0 r[1]=users.first_name 9 ResultRow 1 1 0 0 output=r[1] 10 NextAsync 1 0 0 0 11 NextAwait 1 7 0 0 12 Halt 0 0 0 0 13 Transaction 0 0 0 0 write=false 14 Goto 0 1 0 0 ``` one column index order by, backwards: ```sql limbo> explain select first_name from users order by age desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 13 0 0 Start at 13 1 OpenReadAsync 0 2 0 0 table=users, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 274 0 0 table=age_idx, root=274 4 OpenReadAwait 0 0 0 0 5 LastAsync 1 0 0 0 6 LastAwait 1 0 0 0 7 DeferredSeek 1 0 0 0 8 Column 0 1 1 0 r[1]=users.first_name 9 ResultRow 1 1 0 0 output=r[1] 10 PrevAsync 1 0 0 0 11 PrevAwait 1 0 0 0 12 Halt 0 0 0 0 13 Transaction 0 0 0 0 write=false 14 Goto 0 1 0 0 ``` rowid seek, backwards: ```sql limbo> explain select * from users where id < 100 order by id desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 19 0 0 Start at 19 1 OpenReadAsync 0 2 0 0 table=users, root=2 2 OpenReadAwait 0 0 0 0 3 Integer 100 11 0 0 r[11]=100 4 SeekLT 0 18 11 0 5 RowId 0 1 0 0 r[1]=users.rowid 6 Column 0 1 2 0 r[2]=users.first_name 7 Column 0 2 3 0 r[3]=users.last_name 8 Column 0 3 4 0 r[4]=users.email 9 Column 0 4 5 0 r[5]=users.phone_number 10 Column 0 5 6 0 r[6]=users.address 11 Column 0 6 7 0 r[7]=users.city 12 Column 0 7 8 0 r[8]=users.state 13 Column 0 8 9 0 r[9]=users.zipcode 14 Column 0 9 10 0 r[10]=users.age 15 ResultRow 1 10 0 0 output=r[1..10] 16 PrevAsync 0 0 0 0 17 PrevAwait 0 0 0 0 18 Halt 0 0 0 0 19 Transaction 0 0 0 0 write=false 20 Goto 0 1 0 0 ``` two column order by, setup: ```sql cargo run dualpk.db Limbo v0.0.18-pre.3 Enter ".help" for usage hints. limbo> .schema CREATE TABLE a(b,c,d,e, primary key (d,c)); ``` two column order by, forwards: ```sql limbo> explain select * from a order by d,c; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 RewindAsync 1 0 0 0 6 RewindAwait 1 15 0 0 Rewind table sqlite_autoindex_a_1 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 NextAsync 1 0 0 0 14 NextAwait 1 7 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, forwards with index seek: ```sql limbo> explain select * from a where d > 100 order by d,c; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 Integer 100 5 0 0 r[5]=100 6 SeekGT 1 15 5 0 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 NextAsync 1 0 0 0 14 NextAwait 1 7 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, forwards with index scan and termination condition: ```sql limbo> explain select * from a where d < 100 order by d,c; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 18 0 0 Start at 18 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 Null 0 5 0 0 r[5]=NULL 6 SeekGT 1 17 5 0 7 Integer 100 6 0 0 r[6]=100 8 IdxGE 1 17 6 0 9 DeferredSeek 1 0 0 0 10 Column 0 0 1 0 r[1]=a.b 11 Column 0 1 2 0 r[2]=a.c 12 Column 0 2 3 0 r[3]=a.d 13 Column 0 3 4 0 r[4]=a.e 14 ResultRow 1 4 0 0 output=r[1..4] 15 NextAsync 1 0 0 0 16 NextAwait 1 7 0 0 17 Halt 0 0 0 0 18 Transaction 0 0 0 0 write=false 19 Goto 0 1 0 0 ``` two column order by, backwards: ```sql limbo> explain select * from a order by d desc,c desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 LastAsync 1 0 0 0 6 LastAwait 1 0 0 0 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 PrevAsync 1 0 0 0 14 PrevAwait 1 0 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, backwards with index seek: ```sql limbo> explain select * from a where d < 100 order by d desc,c desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 Integer 100 5 0 0 r[5]=100 6 SeekLT 1 15 5 0 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 PrevAsync 1 0 0 0 14 PrevAwait 1 0 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, backwards with index scan and termination condition: ```sql limbo> explain select * from a where d > 100 order by d desc,c desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 18 0 0 Start at 18 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 LastAsync 1 0 0 0 6 LastAwait 1 0 0 0 7 Integer 100 6 0 0 r[6]=100 8 IdxLE 1 17 6 0 9 DeferredSeek 1 0 0 0 10 Column 0 0 1 0 r[1]=a.b 11 Column 0 1 2 0 r[2]=a.c 12 Column 0 2 3 0 r[3]=a.d 13 Column 0 3 4 0 r[4]=a.e 14 ResultRow 1 4 0 0 output=r[1..4] 15 PrevAsync 1 0 0 0 16 PrevAwait 1 0 0 0 17 Halt 0 0 0 0 18 Transaction 0 0 0 0 write=false 19 Goto 0 1 0 0 ``` Reviewed-by: Preston Thorpe (@PThorpe92) Closes #1209