colexec: cfetcher errors on setup when indexed column contains unhand…

…led type

Fixes cockroachdb#42994.

Indexed columns are always decoded by the fetcher, even if they are unneeded.
This PR adds the check to cfetcher initialization to error out if an indexed
column is of an unneeded type.

Release note (bug fix): Fixed a bug where scanning an index of an unsupported
type with the vectorized engine would lead to an internal error.

pkg/sql/colexec/cfetcher.go

@@ -268,30 +268,45 @@ func (rf *cFetcher) Init(
 	}
 	sort.Sort(m)
 	colDescriptors := tableArgs.Cols
-	typs := make([]coltypes.T, len(colDescriptors))
-	for i := range typs {
-		typs[i] = typeconv.FromColumnType(&colDescriptors[i].Type)
-		if typs[i] == coltypes.Unhandled && tableArgs.ValNeededForCol.Contains(i) {
-			// Only return an error if the type is unhandled and needed. If not needed,
-			// a placeholder Vec will be created.
-			return errors.Errorf("unhandled type %+v", &colDescriptors[i].Type)
-		}
-	}
 	table := cTableInfo{
 		spans:            tableArgs.Spans,
 		desc:             tableArgs.Desc,
 		colIdxMap:        m,
 		index:            tableArgs.Index,
 		isSecondaryIndex: tableArgs.IsSecondaryIndex,
 		cols:             colDescriptors,
-		typs:             typs,
 
 		// These slice fields might get re-allocated below, so reslice them from
 		// the old table here in case they've got enough capacity already.
 		indexColOrdinals:       oldTable.indexColOrdinals[:0],
 		extraValColOrdinals:    oldTable.extraValColOrdinals[:0],
 		allExtraValColOrdinals: oldTable.allExtraValColOrdinals[:0],
 	}
+
+	// All columns that are part of the index key will be decoded when reading a key. Since some types
+	// are not supported by the vectorized engine, we should error out during setup if some needed columns
+	// or columns we decode always will be attempted to be decoded.
+	typs := make([]coltypes.T, len(colDescriptors))
+	for i := range typs {
+		typs[i] = typeconv.FromColumnType(&colDescriptors[i].Type)
+	}
+	var indexedCols util.FastIntSet
+	for _, colID := range tableArgs.Index.ColumnIDs {
+		indexedCols.Add(int(colID))
+	}
+	if cHasExtraCols(&table) {
+		for _, colID := range tableArgs.Index.ExtraColumnIDs {
+			indexedCols.Add(int(colID))
+		}
+	}
+	for i := range typs {
+		if typs[i] == coltypes.Unhandled && (tableArgs.ValNeededForCol.Contains(i) || indexedCols.Contains(int(colDescriptors[i].ID))) {
+			// Only return an error if the type is unhandled and needed. If not needed,
+			// a placeholder Vec will be created.
+			return errors.Errorf("unhandled type %+v", &colDescriptors[i].Type)
+		}
+	}
+	table.typs = typs
 	rf.machine.batch = allocator.NewMemBatch(typs)
 	rf.machine.colvecs = rf.machine.batch.ColVecs()
 

pkg/sql/logictest/testdata/logic_test/vectorize

@@ -1006,3 +1006,13 @@ SELECT * FROM t_42816 ORDER BY a OFFSET 1020 LIMIT 10
 1023
 1024
 1025
+
+# Regression test for #42994
+statement ok
+CREATE TABLE t42994 (a int primary key, b bit, index i (a, b));
+INSERT INTO t42994 VALUES (1, 1::BIT);
+
+query I
+SELECT a FROM t42994@i
+----
+1