optimizer: filter scan rule

[crwen]

risinglight/src/planner/rules/range.rs

Lines 88 to 100 in 0e4a846

	pub fn filter_scan_rule() -> Vec<Rewrite> { vec![
	// pushdown range condition to scan
	rw!("filter-scan";
	"(filter ?cond (scan ?table ?columns true))" =>
	"(scan ?table ?columns ?cond)"
	if is_primary_key_range("?cond")
	),
	rw!("filter-scan-1";
	"(filter (and ?cond1 ?cond2) (scan ?table ?columns true))" =>
	"(filter ?cond2 (scan ?table ?columns ?cond1))"
	if is_primary_key_range("?cond1")
	),
	]}

Here's my understanding: When there are predicates on primary key, we should push them down to the storage layer. Is that right?

But it seems not to work when I execute statements like select pk from t where pk > 1. And the filter passed to scan function is always None. It looks like these:

> explain select a from t2 where a > 17;
Filter { cond: > { lhs: a, rhs: 17 }, cost: 68.4, rows: 20 }
└── Scan { table: t2, list: [ a ], filter: null, cost: 40, rows: 40 }

Maybe the true in "(scan ?table ?columns true)" should be replaced to null? Because it seems to work if I change it.

> explain select a from t2 where a > 17;
Scan { table: t2, list: [ a ], filter: > { lhs: a, rhs: 17 }, cost: 40, rows: 40 }

[skyzh]

maybe related: #795? But it's a known issue and if you want to fix that, please submit a pull request, thanks!

[crwen]

It seems like that the filter is true by default, instead of null. So the solution may be like this in #795?

risinglight/src/binder/table.rs

Lines 60 to 70 in cd03496

	fn bind_table_factor(&mut self, table: TableFactor) -> Result {
	match table {
	TableFactor::Table { name, alias, .. } => {
	let (table_id, is_internal) = self.bind_table_id(&name)?;
	let cols = self.bind_table_def(&name, alias, false)?;
	let id = if is_internal {
	self.egraph.add(Node::Internal([table_id, cols]))
	} else {
	let true_ = self.egraph.add(Node::true_());
	self.egraph.add(Node::Scan([table_id, cols, true_]))
	};