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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[FlightSQL][JDBC] NullPointerException in DatabaseMetadata methods when SqlInfo is unavailable","articleBody":"## Describe the bug\n\nMultiple 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()`.\n\n## Affected Methods\n\nAll 68+ DatabaseMetadata methods that rely on `getSqlInfoAndCacheIfCacheIsEmpty()` are affected, including:\n\n### Integer-returning methods (20 methods)\n- `getMaxBinaryLiteralLength()`\n- `getMaxCharLiteralLength()`\n- `getMaxColumnNameLength()`\n- `getMaxColumnsInGroupBy()`\n- `getMaxColumnsInIndex()`\n- `getMaxColumnsInOrderBy()`\n- `getMaxColumnsInSelect()`\n- `getMaxColumnsInTable()`\n- `getMaxConnections()`\n- `getMaxCursorNameLength()`\n- `getMaxIndexLength()`\n- `getMaxSchemaNameLength()`\n- `getMaxProcedureNameLength()`\n- `getMaxCatalogNameLength()`\n- `getMaxRowSize()`\n- `getMaxStatementLength()`\n- `getMaxStatements()`\n- `getMaxTableNameLength()`\n- `getMaxTablesInSelect()`\n- `getMaxUserNameLength()`\n\n### Boolean-returning methods (30 methods)\n- `supportsColumnAliasing()`\n- `nullPlusNonNullIsNull()`\n- `supportsTableCorrelationNames()`\n- `supportsDifferentTableCorrelationNames()`\n- `supportsExpressionsInOrderBy()`\n- `supportsOrderByUnrelated()`\n- `supportsLikeEscapeClause()`\n- `supportsNonNullableColumns()`\n- `supportsIntegrityEnhancementFacility()`\n- `isCatalogAtStart()`\n- `supportsSelectForUpdate()`\n- `supportsStoredProcedures()`\n- `supportsCorrelatedSubqueries()`\n- `doesMaxRowSizeIncludeBlobs()`\n- `supportsTransactions()`\n- `dataDefinitionCausesTransactionCommit()`\n- `dataDefinitionIgnoredInTransactions()`\n- `supportsBatchUpdates()`\n- `supportsSavepoints()`\n- `supportsNamedParameters()`\n- `locatorsUpdateCopy()`\n- `supportsStoredFunctionsUsingCallSyntax()`\n\n### Support level methods (18 methods)\n- `getDefaultTransactionIsolation()`\n- `supportsGroupBy()`\n- `supportsGroupByUnrelated()`\n- `supportsMinimumSQLGrammar()`\n- `supportsCoreSQLGrammar()`\n- `supportsExtendedSQLGrammar()`\n- `supportsANSI92EntryLevelSQL()`\n- `supportsANSI92IntermediateSQL()`\n- `supportsANSI92FullSQL()`\n- `supportsOuterJoins()`\n- `supportsFullOuterJoins()`\n- `supportsLimitedOuterJoins()`\n- `supportsSchemasInProcedureCalls()`\n- `supportsSchemasInIndexDefinitions()`\n- `supportsSchemasInPrivilegeDefinitions()`\n- `supportsCatalogsInIndexDefinitions()`\n- `supportsCatalogsInPrivilegeDefinitions()`\n- `supportsPositionedDelete()`\n- `supportsPositionedUpdate()`\n- `supportsSubqueriesInComparisons()`\n- `supportsSubqueriesInExists()`\n- `supportsSubqueriesInIns()`\n- `supportsSubqueriesInQuantifieds()`\n- `supportsUnion()`\n- `supportsUnionAll()`\n\n### Map-returning methods\n- `supportsConvert()`\n\n## Component(s)\n\n- FlightSQL\n- JDBC\n\n## To Reproduce\n\n```java\nimport java.sql.*;\nimport java.util.Properties;\n\npublic class DatabaseMetadataTest {\n    public static void main(String[] args) throws SQLException {\n        String url = \"jdbc:arrow-flight-sql://...\";\n        Properties props = new Properties();\n        Driver driver = DriverManager.getDriver(url);\n        try (Connection conn = driver.connect(url, props)) {\n            DatabaseMetaData metaData = conn.getMetaData();\n\n            // All of these throw NullPointerException\n            System.out.println(metaData.getMaxBinaryLiteralLength());\n            System.out.println(metaData.supportsTransactions());\n            System.out.println(metaData.supportsGroupBy());\n        }\n    }\n}\n```\n\n### Error Output\n\n```\nException in thread \"main\" java.lang.NullPointerException: Cannot invoke \"java.lang.Long.intValue()\"\nbecause the return value of \"org.apache.arrow.driver.jdbc.ArrowDatabaseMetadata.getSqlInfoAndCacheIfCacheIsEmpty\n(org.apache.arrow.driver.jdbc.shaded.org.apache.arrow.flight.sql.impl.FlightSql$SqlInfo, java.lang.Class)\" is null\n\tat org.apache.arrow.driver.jdbc.ArrowDatabaseMetadata.getMaxBinaryLiteralLength(ArrowDatabaseMetadata.java:xxx)\n```\n\n## Expected behavior\n\n1. **Option A:** Return sensible defaults when SqlInfo is unavailable:\n   - Integer methods: return `0` (as per JDBC spec for \"no limit\" or \"unknown\")\n   - Boolean methods: return `false` (conservative/safe default)\n   - Support level methods: return appropriate default enums\n   - Map methods: return empty map\n\n2. **Option B:** Throw `SQLException` with a descriptive message indicating the server doesn't support the requested SqlInfo\n\n3. Methods should NOT throw unchecked `NullPointerException` - this violates JDBC contracts and the principle of least surprise\n\n## Environment\n\n**Arrow Version:**\n- 18.3.0\n\n**Java Version:**\n- Java 11+\n\n**OS:**\n- All platforms\n\n### JDBC Specification Reference\n\nPer JDBC 4.3 specification:\n- Methods returning int should return 0 when the limit is unknown or there is no limit\n- Methods returning boolean should return false for unsupported features\n- Methods should throw SQLException for errors, not unchecked exceptions","author":{"url":"https://github.com/merzbird","@type":"Person","name":"merzbird"},"datePublished":"2026-01-29T10:12:42.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/994/arrow-java/issues/994"}