[magnusp]

Fixes #113.

Contract: Hrana 3 governs transport and values, so the pragmas run through execute; java.sql defines the 14-column foreign-key shape, the six primary-key columns, and the 18 type-info columns; xerial/sqlite-jdbc 3.53.4.0 is the behavioral reference for row values and the type table.

Changes

• getImportedKeys, getExportedKeys, and getCrossReference read pragma foreign_key_list (joined to sqlite_schema for constraint names and case-corrected table names) and synthesize the xerial row shape, including KEY_SEQ, update/delete rule constants, FK_NAME, PK_NAME, and DEFERRABILITY.
• getTypeInfo returns the sqlite-jdbc type table: NULL, INTEGER, REAL, TEXT, BLOB, ordered by DATA_TYPE, with the same per-type flags.
• getPrimaryKeys parses a named CONSTRAINT ... PRIMARY KEY from the table SQL and reports it in PK_NAME; inline primary keys keep a NULL PK_NAME.
• Empty databases and tables without foreign keys return well-formed empty result sets, not errors.

Divergences and reference notes

• getCrossReference with both a parent and a child table returns the real matching rows. xerial ends that path in limit 0 and returns no rows. Reason: the issue asks for pragma-driven key metadata, and the both-table form is the useful cross-reference query.
• getPrimaryKeys keeps the driver's existing KEY_SEQ ordering. xerial orders primary-key columns by COLUMN_NAME; ordering is unchanged by this PR and composites remain readable through KEY_SEQ.
• DEFERRABILITY is always importedKeyInitiallyDeferred, matching xerial. pragma foreign_key_list does not expose deferrability.
• Missing FK/PK names are empty strings in imported/exported rows and NULL in getPrimaryKeys, matching xerial.

Evidence at head d6ea8b7 (base 662d066)

Lane	Command	Result
1 regression	./mvnw -pl libsql-jdbc test -Dtest=LibsqlDatabaseMetaDataTest at trunk	Red: 7 failures, 1 error; the new cases fail on the WHERE 0 stubs and missing PK_NAME
1 regression	same at head	Green: 35/35
2 row shape	targeted shape probes	Green: 14 FK columns, rule constants, named FK/PK, xerial type table
3 live sqld	DOCKER_CONFIG=... ./mvnw -pl libsql-itests -am -Dit.test=DatabaseMetaDataIT verify	Green: 2/2; pragmas round-trip through Hrana
4 module	./mvnw -pl libsql-jdbc test	BUILD SUCCESS, 264 tests
5 conformance	./mvnw -pl libsql-conformance -am verify	BUILD SUCCESS, 123 tests, 1 skipped
6 control	./mvnw -pl libsql-conformance -am -Pxerial-control verify	BUILD SUCCESS, 100 tests, 1 skipped
7 format	./mvnw spotless:check	BUILD SUCCESS
8 reactor	./mvnw test	BUILD SUCCESS
9 empty case	-Dtest=LibsqlDatabaseMetaDataTest#emptyDatabaseReturnsWellFormedEmptyKeyMetadata	Green: empty results are well-formed
10 package	./mvnw -pl libsql-jdbc -am package -DskipTests	BUILD SUCCESS; driver jar built
perf	module test, 3 interleaved runs per side	Trunk median 2.05 s, head median 2.09 s (+1.95%, within 10%)

Logs: /tmp/xerial-parity-i113/.

Files outside the plan's Files block

• libsql-itests/src/test/java/com/github/magnusp/libsql/itest/DatabaseMetaDataIT.java is new. Lane 3 requires a live sqld metadata case, and the plan's Files block names no itest file.

Ready for review. Not merged.