Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

A file scan with Limit 0 loses the file's columns, and the CSVOld scan throws

Open
#8,602 5 comments 0 reactions 1 assignee View on GitHub

Maintainers usually reply within 1 day

Nobody has claimed this yet.

Assessment

This issue has not been assessed yet.

Description

What happened?

The Limit on a file-scan source is meant to bound how many rows the operator outputs. It also bounds the sample sourceSchema() reads to infer the columns, so a Limit of 0 leaves the inference nothing to look at and the operator reports a schema that does not describe the file.

The three readers fail differently on the same file. CSV File Scan and JSONL File Scan return a schema with no attributes at all. CSVOld File Scan throws ArrayIndexOutOfBoundsException, because it takes the column names from the header row and the types from the sample, then asks the empty type array for the first header's type.

Zero is a value the property editor accepts, and it is the natural way to ask for no rows. The columns of a file do not depend on how many of its rows the user wants, so a Limit of 0 should give an operator with the file's schema and an empty output, not one with no columns or one that throws.

How to reproduce?

Point a CSVOld File Scan at a CSV with a header and a couple of data rows, set Limit to 0, and run. The execution fails as the executor is constructed, on the operator's own schema inference, before a row is read. The same two steps on a CSV File Scan or a JSONL File Scan instead give downstream operators an operator with no columns.

Set Limit to 1 on any of the three and the schema is correct again, which is what tells the two concerns apart: CSVOldScanSourceOpDesc.sourceSchema reads its inference sample from slice(startOffset, startOffset + limit), and CSVScanSourceOpDesc and JSONLScanSourceOpDesc bound theirs the same way.

Version/Branch

1.4.0-incubating-SNAPSHOT (main)

Commit Hash (Optional)

e7d1676e1

What browsers are you seeing the problem on?

No response

Relevant log output
java.lang.ArrayIndexOutOfBoundsException: Index 0 out of bounds for length 0
	at org.apache.texera.amber.operator.source.scan.csvOld.CSVOldScanSourceOpDesc.$anonfun$sourceSchema$8(CSVOldScanSourceOpDesc.scala:204)
	at org.apache.texera.amber.operator.source.scan.csvOld.CSVOldScanSourceOpDesc.sourceSchema(CSVOldScanSourceOpDesc.scala:201)
	at org.apache.texera.amber.operator.source.scan.csvOld.CSVOldScanSourceOpExec.<init>(CSVOldScanSourceOpExec.scala:38)
Dominant language
Scala
Stars
316
Forks
192
Avg merge
3d 9h
Merged PRs (30d)
136

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from apache/texera

All issues in apache/texera

Similar issues

More Scala issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.