fix: fix tab completion for relation (#12908)

e2e_test/batch/subquery/tab_completion.slt.part

@@ -0,0 +1,25 @@
+# queries from psql tab completion
+
+statement ok
+create table ttttt(x int);
+
+statement ok
+create table tttt(x int);
+
+# select * from tt<tab>
+query I rowsort
+SELECT pg_catalog.quote_ident(c.relname) FROM pg_catalog.pg_class c WHERE c.relkind IN ('r', 'S', 'v', 'm', 'f', 'p') AND substring(pg_catalog.quote_ident(c.relname),1,2)='tt' AND pg_catalog.pg_table_is_visible(c.oid) AND c.relnamespace <> (SELECT oid FROM pg_catalog.pg_namespace WHERE nspname = 'pg_catalog')
+UNION
+SELECT pg_catalog.quote_ident(n.nspname) || '.' FROM pg_catalog.pg_namespace n WHERE substring(pg_catalog.quote_ident(n.nspname) || '.',1,2)='tt' AND (SELECT pg_catalog.count(*) FROM pg_catalog.pg_namespace WHERE substring(pg_catalog.quote_ident(nspname) || '.',1,2) = substring('tt',1,pg_catalog.length(pg_catalog.quote_ident(nspname))+1)) > 1
+UNION
+SELECT pg_catalog.quote_ident(n.nspname) || '.' || pg_catalog.quote_ident(c.relname) FROM pg_catalog.pg_class c, pg_catalog.pg_namespace n WHERE c.relnamespace = n.oid AND c.relkind IN ('r', 'S', 'v', 'm', 'f', 'p') AND substring(pg_catalog.quote_ident(n.nspname) || '.' || pg_catalog.quote_ident(c.relname),1,2)='tt' AND substring(pg_catalog.quote_ident(n.nspname) || '.',1,2) = substring('tt',1,pg_catalog.length(pg_catalog.quote_ident(n.nspname))+1) AND (SELECT pg_catalog.count(*) FROM pg_catalog.pg_namespace WHERE substring(pg_catalog.quote_ident(nspname) || '.',1,2) = substring('tt',1,pg_catalog.length(pg_catalog.quote_ident(nspname))+1)) = 1
+LIMIT 1000
+----
+tttt
+ttttt
+
+statement ok
+drop table tttt;
+
+statement ok
+drop table ttttt;

src/frontend/src/optimizer/plan_visitor/cardinality_visitor.rs

@@ -18,7 +18,6 @@ use std::ops::{Mul, Sub};
 use risingwave_pb::plan_common::JoinType;
 
 use super::{DefaultBehavior, DefaultValue, PlanVisitor};
-use crate::catalog::system_catalog::pg_catalog::PG_NAMESPACE_TABLE_NAME;
 use crate::optimizer::plan_node::generic::TopNLimit;
 use crate::optimizer::plan_node::{
     self, PlanNode, PlanTreeNode, PlanTreeNodeBinary, PlanTreeNodeUnary,
@@ -44,18 +43,35 @@ impl CardinalityVisitor {
         // We don't have UNIQUE key now. So we hack here to support some complex queries on
         // system tables.
         // TODO(card): remove this after we have UNIQUE key. https://github.com/risingwavelabs/risingwave/issues/12514
-        if let Some(scan) = input.as_logical_scan()
-            && scan.is_sys_table()
-            && scan.table_name() == PG_NAMESPACE_TABLE_NAME
         {
-            if let Some(nspname) = scan
-                .output_col_idx()
-                .iter()
-                .find(|i| scan.table_desc().columns[**i].name == "nspname") {
-                unique_keys.push([*nspname].into_iter().collect());
+            // Hack for unique key `nspname` on `pg_catalog.pg_namespace`
+            //
+            // LogicalFilter { predicate: (rw_schemas.name = ...) }
+            //  (below is expanded logical view, see src/frontend/src/catalog/system_catalog/pg_catalog/pg_namespace.rs)
+            //  └─LogicalProject { exprs: [rw_schemas.id, rw_schemas.name, rw_schemas.owner, rw_schemas.acl] }
+            //    └─LogicalScan { table: rw_schemas, columns: [id, name, owner, acl] }
+            fn try_get_unique_key_from_pg_namespace(plan: &dyn PlanNode) -> Option<HashSet<usize>> {
+                let proj = plan.as_logical_project()?;
+                if !proj.is_identity() {
+                    return None;
+                }
+                let scan = proj.input();
+                let scan = scan.as_logical_scan()?;
+                if scan.is_sys_table() && scan.table_name() == "rw_schemas" {
+                    if let Some(name) = scan
+                        .output_col_idx()
+                        .iter()
+                        .find(|i| scan.table_desc().columns[**i].name == "name")
+                    {
+                        return Some([*name].into_iter().collect());
+                    }
+                }
+                None
+            }
+            if let Some(unique_key) = try_get_unique_key_from_pg_namespace(input) {
+                unique_keys.push(unique_key);
             }
         }
-
         if unique_keys
             .iter()
             .any(|unique_key| eq_set.is_superset(unique_key))