merzbird opened a new issue, #994:
URL: https://github.com/apache/arrow-java/issues/994
### Describe the bug, including details regarding any error messages,
version, and platform.
## Describe the bug
Multiple DatabaseMetadata methods in the Arrow Flight SQL JDBC driver throw
`NullPointerException` when the server doesn't provide certain SqlInfo values.
The `ArrowDatabaseMetadata.getSqlInfoAndCacheIfCacheIsEmpty()` method returns
`null`, but calling code doesn't handle null defensively before invoking
methods like `.intValue()`, `.booleanValue()`, or `.isEmpty()`.
## Affected Methods
All 68+ DatabaseMetadata methods that rely on
`getSqlInfoAndCacheIfCacheIsEmpty()` are affected, including:
### Integer-returning methods (20 methods)
- `getMaxBinaryLiteralLength()`
- `getMaxCharLiteralLength()`
- `getMaxColumnNameLength()`
- `getMaxColumnsInGroupBy()`
- `getMaxColumnsInIndex()`
- `getMaxColumnsInOrderBy()`
- `getMaxColumnsInSelect()`
- `getMaxColumnsInTable()`
- `getMaxConnections()`
- `getMaxCursorNameLength()`
- `getMaxIndexLength()`
- `getMaxSchemaNameLength()`
- `getMaxProcedureNameLength()`
- `getMaxCatalogNameLength()`
- `getMaxRowSize()`
- `getMaxStatementLength()`
- `getMaxStatements()`
- `getMaxTableNameLength()`
- `getMaxTablesInSelect()`
- `getMaxUserNameLength()`
### Boolean-returning methods (30 methods)
- `supportsColumnAliasing()`
- `nullPlusNonNullIsNull()`
- `supportsTableCorrelationNames()`
- `supportsDifferentTableCorrelationNames()`
- `supportsExpressionsInOrderBy()`
- `supportsOrderByUnrelated()`
- `supportsLikeEscapeClause()`
- `supportsNonNullableColumns()`
- `supportsIntegrityEnhancementFacility()`
- `isCatalogAtStart()`
- `supportsSelectForUpdate()`
- `supportsStoredProcedures()`
- `supportsCorrelatedSubqueries()`
- `doesMaxRowSizeIncludeBlobs()`
- `supportsTransactions()`
- `dataDefinitionCausesTransactionCommit()`
- `dataDefinitionIgnoredInTransactions()`
- `supportsBatchUpdates()`
- `supportsSavepoints()`
- `supportsNamedParameters()`
- `locatorsUpdateCopy()`
- `supportsStoredFunctionsUsingCallSyntax()`
### Support level methods (18 methods)
- `getDefaultTransactionIsolation()`
- `supportsGroupBy()`
- `supportsGroupByUnrelated()`
- `supportsMinimumSQLGrammar()`
- `supportsCoreSQLGrammar()`
- `supportsExtendedSQLGrammar()`
- `supportsANSI92EntryLevelSQL()`
- `supportsANSI92IntermediateSQL()`
- `supportsANSI92FullSQL()`
- `supportsOuterJoins()`
- `supportsFullOuterJoins()`
- `supportsLimitedOuterJoins()`
- `supportsSchemasInProcedureCalls()`
- `supportsSchemasInIndexDefinitions()`
- `supportsSchemasInPrivilegeDefinitions()`
- `supportsCatalogsInIndexDefinitions()`
- `supportsCatalogsInPrivilegeDefinitions()`
- `supportsPositionedDelete()`
- `supportsPositionedUpdate()`
- `supportsSubqueriesInComparisons()`
- `supportsSubqueriesInExists()`
- `supportsSubqueriesInIns()`
- `supportsSubqueriesInQuantifieds()`
- `supportsUnion()`
- `supportsUnionAll()`
### Map-returning methods
- `supportsConvert()`
## Component(s)
- FlightSQL
- JDBC
## To Reproduce
```java
import java.sql.*;
import java.util.Properties;
public class DatabaseMetadataTest {
public static void main(String[] args) throws SQLException {
String url = "jdbc:arrow-flight-sql://...";
Properties props = new Properties();
Driver driver = DriverManager.getDriver(url);
try (Connection conn = driver.connect(url, props)) {
DatabaseMetaData metaData = conn.getMetaData();
// All of these throw NullPointerException
System.out.println(metaData.getMaxBinaryLiteralLength());
System.out.println(metaData.supportsTransactions());
System.out.println(metaData.supportsGroupBy());
}
}
}
```
### Error Output
```
Exception in thread "main" java.lang.NullPointerException: Cannot invoke
"java.lang.Long.intValue()"
because the return value of
"org.apache.arrow.driver.jdbc.ArrowDatabaseMetadata.getSqlInfoAndCacheIfCacheIsEmpty
(org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.flight.sql.impl.FlightSql$SqlInfo,
java.lang.Class)" is null
at
org.apache.arrow.driver.jdbc.ArrowDatabaseMetadata.getMaxBinaryLiteralLength(ArrowDatabaseMetadata.java:xxx)
```
## Expected behavior
1. **Option A (Preferred):** Return sensible defaults when SqlInfo is
unavailable:
- Integer methods: return `0` (as per JDBC spec for "no limit" or
"unknown")
- Boolean methods: return `false` (conservative/safe default)
- Support level methods: return appropriate default enums
- Map methods: return empty map
2. **Option B:** Throw `SQLException` with a descriptive message indicating
the server doesn't support the requested SqlInfo
3. Methods should NOT throw unchecked `NullPointerException` - this violates
JDBC contracts and the principle of least surprise
## Environment
**Arrow Version:**
- Latest version (observed in production use)
**Java Version:**
- Java 11+
**OS:**
- All platforms
### JDBC Specification Reference
Per JDBC 4.3 specification:
- Methods returning int should return 0 when the limit is unknown or there
is no limit
- Methods returning boolean should return false for unsupported features
- Methods should throw SQLException for errors, not unchecked exceptions
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