29.12.11.16 The binary_log_transaction_compression_stats Table

This table shows statistical information for transaction payloads written to the binary log and relay log, and can be used to calculate the effects of enabling binary log transaction compression. For information on binary log transaction compression, see Section 7.4.4.5, “Binary Log Transaction Compression”.

The binary_log_transaction_compression_stats table is populated only when the server instance has a binary log, and the system variable binlog_transaction_compression is set to ON. The statistics cover all transactions written to the binary log and relay log from the time the server was started or the table was truncated. Compressed transactions are grouped by the compression algorithm used, and uncompressed transactions are grouped together with the compression algorithm stated as NONE, so the compression ratio can be calculated.

The binary_log_transaction_compression_stats table has these columns:

• LOG_TYPE

  Whether these transactions were written to the binary log or relay log.

• COMPRESSION_TYPE

  The compression algorithm used to compress the transaction payloads. NONE means the payloads for these transactions were not compressed, which is correct in a number of situations (see Section 7.4.4.5, “Binary Log Transaction Compression”).

• TRANSACTION_COUNTER

  The number of transactions written to this log type with this compression type.

• COMPRESSED_BYTES

  The total number of bytes that were compressed and then written to this log type with this compression type, counted after compression.

• UNCOMPRESSED_BYTES

  The total number of bytes before compression for this log type and this compression type.

• COMPRESSION_PERCENTAGE

  The compression ratio for this log type and this compression type, expressed as a percentage.

• FIRST_TRANSACTION_ID

  The ID of the first transaction that was written to this log type with this compression type.

• FIRST_TRANSACTION_COMPRESSED_BYTES

  The total number of bytes that were compressed and then written to the log for the first transaction, counted after compression.

• FIRST_TRANSACTION_UNCOMPRESSED_BYTES

  The total number of bytes before compression for the first transaction.

• FIRST_TRANSACTION_TIMESTAMP

  The timestamp when the first transaction was written to the log.

• LAST_TRANSACTION_ID

  The ID of the most recent transaction that was written to this log type with this compression type.

• LAST_TRANSACTION_COMPRESSED_BYTES

  The total number of bytes that were compressed and then written to the log for the most recent transaction, counted after compression.

• LAST_TRANSACTION_UNCOMPRESSED_BYTES

  The total number of bytes before compression for the most recent transaction.

• LAST_TRANSACTION_TIMESTAMP

  The timestamp when the most recent transaction was written to the log.

The binary_log_transaction_compression_stats table has no indexes.

TRUNCATE TABLE is permitted for the binary_log_transaction_compression_stats table.