Query with RETURNING clause is extremely slow to compile

[j-tai]

Bug Description

The following query, when used with query_scalar!, takes a very long time to compile.

INSERT INTO users (username, password_hash) VALUES (?, ?) RETURNING id

On my laptop, this takes 39.6 seconds to compile. If I remove the RETURNING clause, then it takes 1.1 seconds.

Also, rustc uses 1.8 GB of memory, which I don't think is normal.

Minimal Reproduction

1. git clone https://github.com/j-tai/sqlx-repro
2. cd sqlx-repro
3. sqlite3 db.sqlite '.read dump.sql' (create the database, this is necessary to reproduce)
4. cargo build
   → Compiling the sqlx-repro crate takes a very long time.
5. Edit src/main.rs (e.g., add a comment or something)
6. cargo build
   → Compiling takes a very long time again.

Output of EXPLAIN

sqlite> EXPLAIN INSERT INTO users (username, password_hash) VALUES (?, ?) RETURNING id;
addr  opcode         p1    p2    p3    p4             p5  comment      
----  -------------  ----  ----  ----  -------------  --  -------------
0     Init           0     31    0                    0   Start at 31
1     OpenWrite      0     2     0     5              0   root=2 iDb=0; users
2     OpenWrite      1     3     0     k(1,)          0   root=3 iDb=0; sqlite_autoindex_users_1
3     SoftNull       2     0     0                    0   r[2]=NULL
4     Variable       1     3     0                    0   r[3]=parameter(1,)
5     Variable       2     4     0                    0   r[4]=parameter(2,)
6     Function       0     0     5     current_timestamp(0)  0   r[5]=func()
7     NewRowid       0     1     0                    0   r[1]=rowid
8     HaltIfNull     1299  2     3     users.username  1   if r[3]=null halt
9     HaltIfNull     1299  2     4     users.password_hash  1   if r[4]=null halt
10    HaltIfNull     1299  2     5     users.created  1   if r[5]=null halt
11    HaltIfNull     1299  2     6     users.privacy  1   if r[6]=null halt
12    Affinity       2     5     0     DBBCC          0   affinity(r[2..6])
13    Noop           0     0     0                    0   prep index sqlite_autoindex_users_1
14    SCopy          3     8     0                    0   r[8]=r[3]; username
15    IntCopy        1     9     0                    0   r[9]=r[1]; rowid
16    MakeRecord     8     2     7                    0   r[7]=mkrec(r[8..9]); for sqlite_autoindex_users_1
17    NoConflict     1     19    8     1              0   key=r[8]
18    Halt           2067  2     0     users.username  2   
19    MakeRecord     2     5     10                   0   r[10]=mkrec(r[2..6])
20    IdxInsert      1     7     8     1              16  key=r[7]
21    Insert         0     10    1     users          57  intkey=r[1] data=r[10]
22    SCopy          1     12    0                    0   r[12]=r[1]
23    MakeRecord     12    1     13                   0   r[13]=mkrec(r[12])
24    NewRowid       3     14    0                    0   r[14]=rowid
25    Insert         3     13    14                   0   intkey=r[14] data=r[13]
26    Rewind         3     30    0                    0   
27      Column         3     0     12                   0   r[12]=
28      ResultRow      12    1     0                    0   output=r[12]
29    Next           3     27    0                    0   
30    Halt           0     0     0                    0   
31    Transaction    0     1     10    0              1   usesStmtJournal=1
32    Integer        0     6     0                    0   r[6]=0
33    OpenEphemeral  3     1     0                    0   nColumn=1
34    Goto           0     1     0                    0

Info

• SQLx version: 0.6.1
• SQLx features enabled: "runtime-tokio-native-tls", "sqlite", "chrono", "migrate", "macros", "offline"
• Database server and version: SQLite 3.37.2 2022-01-06 13:25:41 872ba256cbf61d9290b571c0e6d82a20c224ca3ad82971edc46b29818d5dalt1
• Operating system: Pop!_OS 22.04 LTS
• rustc --version: rustc 1.63.0 (4b91a6ea7 2022-08-08)

[abonander]

Duplicate of #1921

There's a fix in #1946, was waiting on a response from the author.

[j-tai]

Thanks. Did a lot of searches and somehow didn't find that.