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optimizer: fix selectivity estimate on unique index

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UNIQUE indexes will by definition return max 1 row, but we were
falling back to our SELECTIVITY_EQ_FALLBACK for them. This commit
fixes that.
This commit is contained in:
Jussi Saurio 2025-12-10 12:21:31 +02:00
parent 0832637f6f
commit 9821d9a7ca
1 changed files with 14 additions and 9 deletions
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23
core/translate/optimizer/constraints.rs
View file

@ -202,16 +202,18 @@ fn estimate_selectivity(
match op {
ast::Operator::Equals => {
let is_unique = column.is_some_and(|c| c.is_rowid_alias() || c.primary_key());
let is_pk_or_rowid_alias =
column.is_some_and(|c| c.is_rowid_alias() || c.primary_key());
if is_unique {
// For unique/PK columns, selectivity is 1/row_count
if row_count > 0 {
1.0 / row_count as f64
} else {
// Fallback: use hardcoded estimate based on expected table size
1.0 / ESTIMATED_HARDCODED_ROWS_PER_TABLE as f64
}
let selectivity_when_unique = if row_count > 0 {
1.0 / row_count as f64
} else {
// Fallback: use hardcoded estimate based on expected table size
1.0 / ESTIMATED_HARDCODED_ROWS_PER_TABLE as f64
};
if is_pk_or_rowid_alias {
selectivity_when_unique
} else if let Some(col_pos) = column_pos {
// For non-unique columns, find an index containing this column and use its stats
if let Some(indexes) = available_indexes.get(table_name) {
@ -222,6 +224,9 @@ fn estimate_selectivity(
// Only use stats if column is first in index (idx_col_pos == 0)
// because that's when the distinct count is most useful
if idx_col_pos == 0 {
if index.unique {
return selectivity_when_unique;
}
if let Some(stats) = table_stats {
if let Some(idx_stat) = stats.index_stats.get(&index.name) {
// distinct_per_prefix[0] = avg rows per distinct value for first column