The join index row structure diagrams for aligned row format systems differ from those of packed64 format systems by having up to five additional pad byte fields (depending on the data types of the columns defined for Index Value) to get row alignment on an 8-byte boundary. The following table lists each of these pad fields and explains their purpose.
| Pad Byte Field Name | Purpose |
|---|---|
| VARCHAR Offsets Array Alignment Pad Bytes | Aligns VARCHAR offsets array at a 2-byte boundary. |
| Fixed Length Column Alignment Pad Bytes | Aligns fixed length columns. |
| Nullable Length Column Alignment Pad Bytes | Aligns nullable length columns. |
| VARCHAR Column Alignment Pad Bytes | Aligns variable length columns. |
| Trailing Pad Bytes | Aligns entire row on an 8-byte boundary. |
The index columns in a row compressed join index row are stored in packed64 format, adjusted for aligned row format systems by a field of alignment bytes trailing field1 and another field of alignment bytes trailing field2 (if necessary to make the entire row align on a modulo(8) boundary). When you row compress a join index, the column_2_name value set for each row in the index is stored as a minirow. Each minirow consists of a byte length field, an optional presence bits array field, and the column_2_name value set for the minirow.
Vantage does not support PPIs for row-compressed join indexes or column-partitioned join indexes.