[Feature][SDK] Support SQL reserved keywords as source field names (backtick-quoted columns)

[luchunliang]

Description

When a source data field is named after a SQL reserved keyword (e.g. from, select, where), the Transform SDK fails to look up the field correctly. JSQLParser requires such identifiers to be quoted with backticks (e.g. from as from_source), but ColumnParser previously stored the raw output of expr.toString(), which still contained the surrounding backticks. As a result, the SDK ended up looking up from (with backticks) instead of the actual field name from, and the lookup returned null.

Use case

The InLong Transform SDK relies on JSQLParser to parse user-provided transformation SQL. If a field name collides with a SQL reserved keyword, it must be quoted with backticks:

sql
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SELECT from AS from_source, itemid AS itemid FROM source
Without the backticks, JSQLParser raises:

net.sf.jsqlparser.JSQLParserException: Encountered unexpected token: "," ","
at line 1, column 116.
Even when backticks are used, ColumnParser previously stored the raw string from (including the backticks) as the field name. That caused sourceData.getField(rowIndex, "from") to return null, because the real field name in the source data is from.

Steps to Reproduce
Configure a source that contains a field named from (a SQL reserved keyword).
Use the following transform SQL:
sql
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SELECT from AS from_source, itemid AS itemid FROM source
Run the transform.
Expected Behavior
The surrounding backticks should be stripped during parsing, and the SDK should use the unquoted field name (from) to look up the value from the source data.

Actual Behavior (before the fix)
ColumnParser stored the field name as from (with backticks), so the field lookup always returned null.

Proposed Fix
Strip the surrounding backticks in ColumnParser before storing the field name.

File: inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/parser/ColumnParser.java

java
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public ColumnParser(Column expr) {
this.fieldName = this.formatFieldName(expr.toString());
}

public ColumnParser(Function expr) {
this.fieldName = this.formatFieldName(expr.toString());
}

private String formatFieldName(String rawFieldName) {
String tmpFieldName = rawFieldName;
if (tmpFieldName.startsWith("")) { tmpFieldName = tmpFieldName.substring(1); } if (tmpFieldName.endsWith("")) {
tmpFieldName = tmpFieldName.substring(0, tmpFieldName.length() - 1);
}
return tmpFieldName;
}
The same backtick-stripping logic is also applied to select-item aliases in TransformProcessor:

File: inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/TransformProcessor.java

java
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fieldName = exprItem.getAlias().getName();
// Strip surrounding backticks if present
if (fieldName != null && fieldName.length() >= 2
&& fieldName.startsWith("") && fieldName.endsWith("")) {
fieldName = fieldName.substring(1, fieldName.length() - 1);
}
Affected Components
inlong-sdk/transform-sdk
ColumnParser.java — added formatFieldName() to strip backticks
TransformProcessor.java — added backtick stripping for select-item aliases
Test Coverage
Updated a test case in TestCsv2KvProcessor.java to cover a backtick-quoted column name:

java
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// In TestCsv2KvProcessor.java

• ",from as random_seq"
  Notes
  formatFieldName() currently only handles backticks (`). Other quoting styles such as double quotes ("from") or square brackets ([from]) are not stripped. This can be addressed in a follow-up improvement if needed.

Are you willing to submit PR?

• Yes, I am willing to submit a PR!

Code of Conduct

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