Teradata provides the following functions for compressing and uncompressing data. These functions are stored in the TD_SYSFNLIB system database.
| Function Type | UDF Name | Description |
|---|---|---|
| Compress | TransUnicodeToUTF8 | Takes UNICODE character input and stores it in UTF-8 format. This is useful when the characters are in the ASCII script (U+0000 to U+007F) because UTF-8 uses one byte to represent these characters and UNICODE (UTF-16) uses two bytes. |
| Decompress | TransUTF8ToUnicode | Takes the data previously compressed using the TransUnicodeToUTF8 function and converts it back to UNICODE. |
| Compress | LZCOMP | Compresses UNICODE character data using the Lempel-Ziv algorithm. |
| Decompress | LZDECOMP | Uncompresses UNICODE data that was compressed using LZCOMP. |
| Compress | LZCOMP_L | Compresses LATIN character data using the Lempel-Ziv algorithm. |
| Decompress | LZDECOMP_L | Uncompresses LATIN data that was compressed using LZCOMP_L. |
| Compress | CAMSET | Compresses UNICODE character data into partial byte (for example, 4-bit digits or 5-bit alphabetic letters), one byte, or two byte values using a proprietary Teradata algorithm. |
| Decompress | DECAMSET | Uncompresses the UNICODE character data that was compressed using CAMSET. |
| Compress | CAMSET_L | Compresses LATIN character data into partial byte (for example, 4-bit digits or 5-bit alphabetic letters), or one byte values using a proprietary Teradata algorithm. |
| Decompress | DECAMSET_L | Uncompresses the LATIN character data that was compressed using CAMSET_L. |
| Compress | TD_LZ_COMPRESS | Compresses any supported ALC data type or predefined type data using Lempel-Ziv coding. |
| Decompress | TD_LZ_DECOMPRESS | Uncompresses any supported ALC data type or predefined type data that was compressed using TZ_LZ_COMPRESS. |
| Compress | TS_COMPRESS | Compresses TIME and TIMESTAMP data. |
| Decompress | TS_DECOMPRESS | Uncompresses TIME and TIMESTAMP data that was compressed using TS_COMPRESS. |
| Compress | JSON_COMPRESS | Compresses JSON data. |
| Decompress | JSON_DECOMPRESS | Uncompresses the JSON data that was compressed using JSON_COMPRESS. |
For more information about these functions, see Teradata Vantage™ - SQL Functions, Expressions, and Predicates, B035-1145.
If these functions do not provide optimal compression for your data, you may implement your own UDFs for use in compressing and uncompressing table columns. For more information, see Teradata Vantage™ - SQL External Routine Programming, B035-1147.
If you create custom ALC UDFs, make sure to test them thoroughly. If the compression or decompression algorithm fails, compressed data may not be recoverable, or may be corrupted.