mirrors/limbo
1
0
Fork 0
mirror of https://github.com/tursodatabase/limbo.git synced 2025-12-23 08:21:09 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 3

fix/sim: modify existing rows in ALTER COLUMN properly

Browse source 
Bug 1:

apply_snapshot(), which handles committing transaction changes to the
simulator state, had this bug:

let's say a transaction does:
1. ALTER TABLE t ADD COLUMN (e.g., adding 9th column)
2. INSERT INTO t ... (populating all 9 columns)

then apply_snapshot() would:
1. First push the INSERT row (with 9 values) to committed_tables
2. Then detect new_col_count (9) > old_col_count (8) and add NULLs to ALL rows

hence, adding a 10th column to the new row too.

Fix 1:

only add nulls to existing rows that weren't inserted in the same tx after
the ADD COLUMN.

Bug 2:

the exact same thing, but for DROP COLUMN.

Fix 2:

only remove the i'th column from rows that existed prior to the DROP COLUMN
was issued.
This commit is contained in:
Jussi Saurio 2025-12-15 15:01:11 +02:00
parent 90846b4dd1
commit 712eb82382
1 changed files with 11 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

16
simulator/runner/env.rs
View file

@ -226,10 +226,11 @@ where
let new_col_count = current_table.columns.len();
if new_col_count > old_col_count {
// ADD COLUMN: fill with NULL
let nulls_to_add = new_col_count - old_col_count;
// ADD COLUMN: fill with NULL only for rows that need it.
// Rows inserted after ADD COLUMN in the same transaction
// already have the correct number of values.
for row in &mut committed.rows {
for _ in 0..nulls_to_add {
while row.len() < new_col_count {
row.push(SimValue::NULL);
}
}
@ -250,8 +251,13 @@ where
dropped_indices.sort_by(|a, b| b.cmp(a));
for row in &mut committed.rows {
for &idx in &dropped_indices {
row.remove(idx);
// Only remove from rows that have the old column count.
// Rows inserted after DROP COLUMN in the same transaction
// already have the correct (new) number of values.
if row.len() == old_col_count {
for &idx in &dropped_indices {
row.remove(idx);
}
}
}
}