prestodb/presto · error · PrestoException

GENERIC_INTERNAL_ERROR

GENERIC_INTERNAL_ERROR

Error message

Error casting array element to VARCHAR

What it means

Runtime failure in ArrayJoin.arrayJoinProvidedBlock: invoking the generated cast of an array element to VARCHAR threw (e.g. an unrepresentable value or a broken cast function); the caught throwable is rewrapped as this cast error while building the joined output string.

Source

Thrown at presto-main-base/src/main/java/com/facebook/presto/operator/scalar/ArrayJoin.java:340

                continue;
            }

            if (hasOutput) {
                blockBuilder.writeBytes(delimiter, 0, delimiter.length());
            }

            if (arrayBlock.isNull(i)) {
                blockBuilder.writeBytes(nullReplacement, 0, nullReplacement.length());
            }
            else {
                try {
                    Slice slice = (Slice) castFunction.invokeExact(arrayBlock, i, properties);
                    blockBuilder.writeBytes(slice, 0, slice.length());
                }
                catch (Throwable throwable) {
                    // Restore blockBuilder into a consistent state
                    blockBuilder.closeEntry();
                    throw new PrestoException(GENERIC_INTERNAL_ERROR, "Error casting array element to VARCHAR", throwable);
                }
            }

            hasOutput = true;
        }

        blockBuilder.closeEntry();
    }
}

View on GitHub (pinned to 55bb57d202)

Solutions

1. Pre-cast elements to VARCHAR and handle failures explicitly with TRY_CAST
2. Replace nulls using array_join's null-replacement argument instead of relying on casts of nulls
3. Filter out elements that cannot be cast to VARCHAR before joining

When it happens

Trigger: Thrown at presto-main-base/src/main/java/com/facebook/presto/operator/scalar/ArrayJoin.java:340 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/a4adc8a2d73ee814. Report an issue: GitHub.