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fix: avoid superfluous ALTER TABLE migrations #11

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Merged
jvatic merged 2 commits into from
Apr 9, 2026
+41 −13
Merged

fix: avoid superfluous ALTER TABLE migrations #11

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4a5730c
fix: don't generate empty ALTER TABLE when nothing changed
jvatic Apr 9, 2026
0170ab7
fix: column names are equal regardless of quote style
jvatic Apr 9, 2026
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16 changes: 10 additions & 6 deletions src/diff.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -339,14 +339,14 @@ fn compare_create_table(a: &CreateTable, b: &CreateTable) -> Option<Vec<Statemen
return None;
}

let a_column_names: HashSet<_> = a.columns.iter().map(|c| c.name.clone()).collect();
let b_column_names: HashSet<_> = b.columns.iter().map(|c| c.name.clone()).collect();
let a_column_names: HashSet<_> = a.columns.iter().map(|c| c.name.value.clone()).collect();
let b_column_names: HashSet<_> = b.columns.iter().map(|c| c.name.value.clone()).collect();

let ops = a
let operations: Vec<_> = a
.columns
.iter()
.filter_map(|ac| {
if b_column_names.contains(&ac.name) {
if b_column_names.contains(&ac.name.value) {
None
} else {
// drop column if it only exists in `a`
Expand All @@ -359,7 +359,7 @@ fn compare_create_table(a: &CreateTable, b: &CreateTable) -> Option<Vec<Statemen
}
})
.chain(b.columns.iter().filter_map(|bc| {
if a_column_names.contains(&bc.name) {
if a_column_names.contains(&bc.name.value) {
None
} else {
// add the column if it only exists in `b`
Expand All @@ -373,11 +373,15 @@ fn compare_create_table(a: &CreateTable, b: &CreateTable) -> Option<Vec<Statemen
}))
.collect();

if operations.is_empty() {
return None;
}

Some(vec![Statement::AlterTable {
name: a.name.clone(),
if_exists: a.if_not_exists,
only: false,
operations: ops,
operations,
location: None,
on_cluster: a.on_cluster.clone(),
iceberg: false,
Expand Down
36 changes: 30 additions & 6 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -173,17 +173,41 @@ mod tests {
#[test]
fn diff_create_table() {
run_test_cases(
vec![TestCase {
dialect: Dialect::Generic,
sql_a: "CREATE TABLE foo(\
vec![
TestCase {
dialect: Dialect::Generic,
sql_a: "CREATE TABLE foo(\
id int PRIMARY KEY
)",
sql_b: "CREATE TABLE foo(\
sql_b: "CREATE TABLE foo(\
id int PRIMARY KEY
);\
CREATE TABLE bar (id INT PRIMARY KEY);",
expect: "CREATE TABLE bar (id INT PRIMARY KEY);",
}],
expect: "CREATE TABLE bar (id INT PRIMARY KEY);",
},
TestCase {
dialect: Dialect::Generic,
sql_a: "CREATE TABLE foo(\
id int PRIMARY KEY
)",
sql_b: "CREATE TABLE foo(\
\"id\" int PRIMARY KEY
);\
CREATE TABLE bar (id INT PRIMARY KEY);",
expect: "CREATE TABLE bar (id INT PRIMARY KEY);",
},
TestCase {
dialect: Dialect::Generic,
sql_a: "CREATE TABLE foo(\
\"id\" int PRIMARY KEY
)",
sql_b: "CREATE TABLE foo(\
id int PRIMARY KEY
);\
CREATE TABLE bar (id INT PRIMARY KEY);",
expect: "CREATE TABLE bar (id INT PRIMARY KEY);",
},
],
|ast_a, ast_b| ast_a.diff(&ast_b),
);
}
Expand Down
2 changes: 1 addition & 1 deletion src/migration.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -265,7 +265,7 @@ fn migrate_alter_table(
t.columns.push(column_def.clone());
}
AlterTableOperation::DropColumn { column_name, .. } => {
t.columns.retain(|c| c.name != *column_name);
t.columns.retain(|c| c.name.value != *column_name.value);
}
AlterTableOperation::AlterColumn { column_name, op } => {
t.columns.iter_mut().for_each(|c| {
Expand Down
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