Postgres Parameter Parsing Error with JSON Object Containing Commas

Based on the documentation and common issues guidance, it appears that passing a JSON object via query parameters in a Postgres query can cause issues because n8n splits items using commas. In your case, the commas in the JSON are being interpreted as separate parameter delimiters rather than as part of a single JSON value. This isn’t a bug per se but rather a limitation of how query parameters are parsed in n8n when the value is not a “simple” value.

Recommendations:

1. Stringify the JSON: Rather than passing the JSON object directly, convert it into a string (using JSON.stringify or a similar method). Then, in your query, cast this string to the desired JSON type (for example, using $1::jsonb). This ensures that the entire JSON is treated as one parameter. For example:

   SQLCopied
   SELECT * FROM my_table WHERE data = $1::jsonb;

   And in your Query Parameters field, pass:

   JSCopied
   JSON.stringify($json.myJSON)

2. Ensure Single Parameter Usage: The approach used with query parameters in n8n assumes either a single simple value or an array of simple values. By stringifying your JSON object, you avoid the comma separation issue because the whole JSON string is passed as a single parameter value.

3. Double-check Parameter Placeholders: If you’re dynamically constructing parts of your query (for example, building a list of placeholders), consider whether that dynamic construction correctly handles JSON strings. Usually, the practice of using expressions for index-based placeholders is intended for simpler values rather than nested JSON objects.

Using these techniques should prevent the query parser from misinterpreting the commas and stop the “The input string ended unexpectedly” error.

Let me know if you need further assistance with this setup!