Amazon Redshift will no longer support the creation of new Python UDFs starting Patch 198. Existing Python UDFs will continue to function until June 30, 2026. For more information, see the [ blog post ](https://aws.amazon.com/blogs/big-data/amazon-redshift-python-user-defined-functions-will-reach-end-of-support-after-june-30-2026/). 

# SYS\_ANALYZE\_COMPRESSION\_HISTORY
<a name="r_SYS_ANALYZE_COMPRESSION_HISTORY"></a>

Records details for compression analysis operations during COPY or ANALYZE COMPRESSION commands.

SYS\_ANALYZE\_COMPRESSION\_HISTORY is visible to all users. Superusers can see all rows; regular users can see only their own data. For more information, see [Visibility of data in system tables and views](cm_chap_system-tables.md#c_visibility-of-data).

## Table columns
<a name="r_SYS_ANALYZE_COMPRESSION_HISTORY-table-columns2"></a>


| Column name  | Data type  | Description  | 
| --- | --- | --- | 
| user\_id | integer | The ID of the user who generated the entry. | 
| start\_time | timestamp | The time when the compression analysis operation started. | 
| transaction\_id | bigint | The transaction ID of the compression analysis operation. | 
| table\_id | integer | The table ID of the table that was analyzed. | 
| table\_name | character(128) | The name of the table that was analyzed. | 
| column\_position | integer | The index of the column in the table that was analyzed to determine the compression encoding. | 
| old\_encoding | character(15) | The encoding type before compression analysis. | 
| new\_encoding | character(15) | The encoding type after compression analysis. | 
| mode | character(14) | [See the AWS documentation website for more details](http://docs.aws.amazon.com/redshift/latest/dg/r_SYS_ANALYZE_COMPRESSION_HISTORY.html)  | 

## Sample queries
<a name="r_SYS_ANALYZE_COMPRESSION_HISTORY-sample-queries2"></a>

The following example inspects the details of compression analysis on the `lineitem` table by the last COPY command run in the same session. 

```
select transaction_id, table_id, btrim(table_name) as table_name, column_position, old_encoding, new_encoding, mode 
from sys_analyze_compression_history
where transaction_id = (select transaction_id from sys_query_history where query_id = pg_last_copy_id()) order by column_position;
                
 transaction_id  |  table_id   | table_name | column_position |  old_encoding   |  new_encoding   |      mode
-----------------+-------------+------------+-----------------+-----------------+-----------------+-------------
      8196       |   248126    | lineitem   |        0        | mostly32        | mostly32        | ON
      8196       |   248126    | lineitem   |        1        | mostly32        | lzo             | ON
      8196       |   248126    | lineitem   |        2        | lzo             | delta32k        | ON
      8196       |   248126    | lineitem   |        3        | delta           | delta           | ON
      8196       |   248126    | lineitem   |        4        | bytedict        | bytedict        | ON
      8196       |   248126    | lineitem   |        5        | mostly32        | mostly32        | ON
      8196       |   248126    | lineitem   |        6        | delta           | delta           | ON
      8196       |   248126    | lineitem   |        7        | delta           | delta           | ON
      8196       |   248126    | lineitem   |        8        | lzo             | zstd            | ON
      8196       |   248126    | lineitem   |        9        | runlength       | zstd            | ON
      8196       |   248126    | lineitem   |       10        | delta           | lzo             | ON
      8196       |   248126    | lineitem   |       11        | delta           | delta           | ON
      8196       |   248126    | lineitem   |       12        | delta           | delta           | ON
      8196       |   248126    | lineitem   |       13        | bytedict        | zstd            | ON
      8196       |   248126    | lineitem   |       14        | bytedict        | zstd            | ON
      8196       |   248126    | lineitem   |       15        | text255         | zstd            | ON
(16 rows)
```