sql: avoid writing to column families that do not exist in the primar…

…y index

Previously, if a new column family was added during an add
column and an update/insert occurred concurrently, we could
end up writing to this new column family in any primary index.
This was inadequate because if the primary index did not store
the column, then runtime will have trouble reading data from this
table, since after a rollback the added column / column family
will get cleaned up from the table descriptor. To address this,
this patch avoids writing any columns not stored within an index
descriptor.

Fixes: #99950

Release note (bug fix): Concurrent DML while adding
a new column with a new column family can lead to
corruption in the existing primary index. If a rollback
occurs the table may no longer be accessible.

pkg/sql/row/writer.go

@@ -139,7 +139,11 @@ func prepareInsertOrUpdateBatch(
 			if !ok {
 				continue
 			}
-
+			// Skip any values with a default ID not stored in the primary index,
+			// which can happen if we are adding new columns,
+			if skip := helper.SkipColumnNotInPrimaryIndexValue(family.DefaultColumnID, values[idx]); skip {
+				continue
+			}
 			typ := fetchedCols[idx].GetType()
 			marshaled, err := valueside.MarshalLegacy(typ, values[idx])
 			if err != nil {

pkg/sql/rowenc/index_encoding.go

@@ -1079,6 +1079,11 @@ func EncodePrimaryIndex(
 		// The decoders expect that column family 0 is encoded with a TUPLE value tag, so we
 		// don't want to use the untagged value encoding.
 		if len(family.ColumnIDs) == 1 && family.ColumnIDs[0] == family.DefaultColumnID && family.ID != 0 {
+			// Single column value families which are not stored can be skipped, these
+			// may exist temporarily while adding a column.
+			if !storedColumns.Contains(family.DefaultColumnID) {
+				return nil
+			}
 			datum := findColumnValue(family.DefaultColumnID, colMap, values)
 			// We want to include this column if its value is non-null or
 			// we were requested to include all of the columns.