PostgreSQL throws this FDW error when the declared length of a character or binary column does not match the length actually supplied or expected during foreign table operations.
fdw_invalid_string_length_or_buffer_length appears when a PostgreSQL foreign table receives a string or bytea value whose length differs from the declared column length. Align the local column definition with the remote type or explicitly cast the value to resolve the error.
fdw_invalid_string_length_or_buffer_length
The error comes from PostgreSQLs SQL/MED layer when a Foreign Data Wrapper (FDW) transfers data between the local server and a remote source. PostgreSQL validates the reported string length or buffer length against the column definition. If the two lengths differ, it raises condition HV090.
The condition protects the local server from writing or reading truncated or over-long values.
Fixing it keeps data consistent and prevents silent data loss.
The error surfaces during SELECT, INSERT, or UPDATE on a foreign table. It is common when the local column is defined as CHAR(n), VARCHAR(n), or BYTEA with a different limit than the remote column or returned value.
FDW extensions such as postgres_fdw, mysql_fdw, and odbc_fdw can all trigger the error if column length metadata becomes inconsistent.
Ignoring the error blocks queries and ETL jobs.
Applications may time out, and replication pipelines can stall.
Aligning column definitions ensures reliable cross-database operations.
Length mismatch between the local foreign table column definition and the remote table definition is the primary cause.
Explicit casts that shorten or expand strings without updating the column length trigger the error when the FDW validates the buffer.
Incorrect encoding or multibyte characters can raise the error if the character count differs from the byte length PostgreSQL expects.
First compare local and remote column data types and size limits.
Make them identical or wider on the local side.
Use ALTER FOREIGN TABLE to adjust column types, or recreate the mapping with CREATE FOREIGN TABLE that matches remote definitions.
If you cannot change the mapping, cast the offending column in the SELECT list or INSERT statement so the value length complies with the declared size.
Remote VARCHAR(50) but local VARCHAR(40) - change the local column to VARCHAR(50).
Remote TEXT but local CHAR(10) - switch the local column to TEXT or use SUBSTRING() to trim values in queries.
Binary data longer than expected - store as BYTEA without a length modifier.
Create foreign tables with IMPORT FOREIGN SCHEMA to auto-copy remote column definitions and prevent manual size errors.
Automate schema drift checks in CI pipelines or with Galaxys AI copilot to flag length mismatches before deployment.
Favor unbounded TEXT for variable strings unless strict limits are required.
HV00B fdw_unable_to_create_execution - occurs when FDW cannot start a remote statement.
HV004 fdw_invalid_data_type - raised when a column type has no local equivalent.
42804 datatype_mismatch - appears on local tables for similar length conflicts.
.
Usually not. The FDW accurately reports a schema mismatch. Align column definitions to resolve.
No safe GUC exists. The check prevents corruption. Fix the schema instead.
Yes. Multibyte encodings can inflate byte length. Ensure both servers share the same client_encoding.
Galaxys editor surfaces remote and local column metadata side by side and its AI copilot suggests ALTER statements that fix length mismatches before you run the query.
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