[CALCITE-7667] Improve string-literal encoding in pushdown translators (follow-up)

[rubenada]

Jira Link

CALCITE-7667

Changes Proposed

The original patch for this ticket (fbfdf89) considered that PigLatin escapes a single quote by doubling it (as SQL does); however this is incorrect, it is escaped by using backslash (PigLatin uses backslash as escape character, see https://pig.apache.org/docs/r0.16.0/cont.html).

The current follow-up patch corrects this, and adjusts the corresponding tests.

[mihaibudiu]

I reviewed the other PR, and I asked whether results were validated.
I think it's too expensive to expect to run real validators for all possible formats Calcite can produce, so we have to rely on developers manually validating the results.

[mihaibudiu]

This approval is conditional on the promise that these results were indeed validated mechanically using a Pig installation.

[rubenada]

My bad @mihaibudiu , I thought that PigAdapterTest.java was doing more than it actually does. Let me check manually...

[rubenada]

@mihaibudiu I have verified locally with pig, and I confirm the new escape syntax is the correct one.
Sorry about the wrong initial patch.

[mihaibudiu]

I would comment on each validated test about the fact it's been checked against Pig. Then this question won't surface again.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
83.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud