How to diagnose and fix the 22P06 nonstandard_use_of_escape_character error code in Postgres.

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The 22P06 error code in PostgreSQL refers to nonstandard_use_of_escape_character. This error is raised when a backslash (\) is used in a string literal without being properly escaped in a context where PostgreSQL expects standard-conforming strings.

PostgreSQL has a configuration parameter called standard_conforming_strings, which, when set to on, causes PostgreSQL to treat backslashes as literal characters in string literals, rather than escape characters. If this parameter is off, a single backslash is treated as an escape character. The SQL standard requires backslashes to be treated as literal characters, which is why the standard_conforming_strings parameter is on by default in modern PostgreSQL versions.

To diagnose this issue, look for string literals containing backslashes in your SQL queries. Here’s an example that would cause the 22P06 error:

SELECT 'C:\Program Files\PostgreSQL\';

If standard_conforming_strings is set to on, PostgreSQL will not treat the backslash as an escape character and will expect another character to follow the backslash, leading to the 22P06 error.

To fix this issue, you have several options:

  1. Use Standard-Conforming Strings: Double the backslashes to properly escape them in the string literal: SELECT 'C:\\Program Files\\PostgreSQL\\';
  2. Use the E Escape String Syntax: If you need to use escape sequences like \n for newline, \t for tab, etc., you can use the E escape string syntax to explicitly mark the string as containing escape sequences: SELECT E'C:\\Program Files\\PostgreSQL\\'; This tells PostgreSQL to interpret the string as an escape string literal, and the backslashes will be treated as escape characters.
  3. Change the Server Setting: Though not recommended because it goes against the SQL standard, you can set standard_conforming_strings to off to revert to the old behavior: SET standard_conforming_strings TO off; However, this is generally discouraged because it can lead to SQL injection vulnerabilities and other issues.

For more details on the use of escape characters in PostgreSQL, you can refer to the PostgreSQL documentation on strings and the Stack Overflow discussion on nonstandard use of escape in a string literal.

To avoid this error, it’s best to adhere to the SQL standard for string literals and use the E escape string syntax when necessary.

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