The server could not decompress a network packet sent by the client, breaking the connection.
MySQL Error 1157: ER_NET_UNCOMPRESS_ERROR means the server failed to decompress a compressed communication packet, usually because of corrupted data, mismatched compression settings, or network glitches. Re-establish the connection and align client-server compression settings to fix the issue.
Couldn't uncompress communication packet
Error 1157 fires when the MySQL server receives a compressed packet it cannot decompress. The server ends the session and returns SQLSTATE 08S01 with the message "Couldn't uncompress communication packet."
The problem appears during data exchange on compressed connections, especially when large result sets or BLOB fields travel across unstable networks.
Fixing it quickly is vital because the client loses its session and any in-flight transaction.
Corrupted TCP segments are a primary cause. If bits flip in transit, the server’s zlib or zstd library cannot inflate the payload and raises error 1157.
Mismatched or buggy compression settings between client and server also trigger the failure.
Older MySQL connectors may send packets in a format the server no longer supports.
Oversized packets can overflow the max_allowed_packet limit after decompression, leading the decompressor to abort and emit the error.
First, reconnect to reset the session. Then set compression_algs=off on the client to verify that the link works without compression.
If the uncompressed link is stable, align versions and enable a safe algorithm such as zstd_stream.
Increase max_allowed_packet on both sides to accommodate the inflated size.
Monitor your network with tcpdump or Wireshark to detect drops or out-of-order segments that could corrupt packets.
Batch exports failing over VPNs often hit this error. Lower net_write_timeout and resend smaller chunks to reduce risk.
ETL tools on JDBC 5.1.49 may negotiate an outdated compression flag.
Upgrading to Connector/J 8.x resolves the error.
Keep client and server versions in sync and enable only modern compression algorithms.
Set max_allowed_packet comfortably above your largest expected row after decompression.
Use Galaxy’s query editor to test large result sets locally before running them in production, catching oversize packets early.
MySQL Error 1153 - Packet too large: raise max_allowed_packet and check BLOB sizes.
MySQL Error 2006 - MySQL server has gone away: often a follow-on effect; investigate network timeouts and packet corruption.
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Disabling compression increases bandwidth use but is a good diagnostic step. Once stable, re-enable with a modern algorithm.
MySQL 8.0.18 and later support zstd_stream and zstd_level3. Earlier versions rely on zlib only.
The variable supports up to 1GB in MySQL 8.0. Set it wide enough for your largest row plus overhead.
Yes. Galaxy shows packet statistics in the result footer, alerting you when result sets approach configured limits.
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