feat(jdbc): read key and type metadata from SQLite pragmas

getImportedKeys, getExportedKeys, and getCrossReference now map pragma foreign_key_list rows to the JDBC shape, getTypeInfo returns the sqlite-jdbc type table, and getPrimaryKeys reports the parsed constraint name in PK_NAME.

Fixes #113

Author: magnusp

libsql-itests/src/test/java/com/github/magnusp/libsql/itest/DatabaseMetaDataIT.java

@@ -0,0 +1,108 @@
+package com.github.magnusp.libsql.itest;
+
+import org.junit.jupiter.api.Test;
+
+import java.sql.Connection;
+import java.sql.DatabaseMetaData;
+import java.sql.DriverManager;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class DatabaseMetaDataIT extends SqldContainerBase {
+
+    private String getDriverJdbcUrl() {
+        return "jdbc:libsql:" + getHttpUrl();
+    }
+
+    @Test
+    void keyAndTypeMetadataRoundTripThroughHrana() throws SQLException {
+        try (Connection conn = DriverManager.getConnection(getDriverJdbcUrl())) {
+            try (Statement s = conn.createStatement()) {
+                s.execute("CREATE TABLE meta_parent (id INTEGER, label TEXT, "
+                        + "CONSTRAINT pk_meta_parent PRIMARY KEY (id))");
+                s.execute("CREATE TABLE meta_child (id INTEGER, parent_id INTEGER, "
+                        + "CONSTRAINT fk_meta_child_parent FOREIGN KEY (parent_id) "
+                        + "REFERENCES meta_parent (id) ON DELETE CASCADE)");
+            }
+            DatabaseMetaData metadata = conn.getMetaData();
+
+            try (ResultSet rs = metadata.getPrimaryKeys(null, null, "meta_parent")) {
+                assertThat(rs.next()).isTrue();
+                assertThat(rs.getString("COLUMN_NAME")).isEqualTo("id");
+                assertThat(rs.getInt("KEY_SEQ")).isEqualTo(1);
+                assertThat(rs.getString("PK_NAME")).isEqualTo("pk_meta_parent");
+                assertThat(rs.next()).isFalse();
+            }
+
+            try (ResultSet rs = metadata.getImportedKeys(null, null, "meta_child")) {
+                assertThat(rs.next()).isTrue();
+                assertThat(rs.getString("PKTABLE_NAME")).isEqualTo("meta_parent");
+                assertThat(rs.getString("PKCOLUMN_NAME")).isEqualTo("id");
+                assertThat(rs.getString("FKTABLE_NAME")).isEqualTo("meta_child");
+                assertThat(rs.getString("FKCOLUMN_NAME")).isEqualTo("parent_id");
+                assertThat(rs.getInt("KEY_SEQ")).isEqualTo(1);
+                assertThat(rs.getInt("DELETE_RULE")).isEqualTo(DatabaseMetaData.importedKeyCascade);
+                assertThat(rs.getString("FK_NAME")).isEqualTo("fk_meta_child_parent");
+                assertThat(rs.getString("PK_NAME")).isEqualTo("pk_meta_parent");
+                assertThat(rs.next()).isFalse();
+            }
+
+            try (ResultSet rs = metadata.getExportedKeys(null, null, "meta_parent")) {
+                assertThat(rs.next()).isTrue();
+                assertThat(rs.getString("PKTABLE_NAME")).isEqualTo("meta_parent");
+                assertThat(rs.getString("FKTABLE_NAME")).isEqualTo("meta_child");
+                assertThat(rs.getString("FK_NAME")).isEqualTo("fk_meta_child_parent");
+                assertThat(rs.getString("PK_NAME")).isEqualTo("pk_meta_parent");
+                assertThat(rs.next()).isFalse();
+            }
+
+            try (ResultSet rs = metadata.getCrossReference(null, null, "meta_parent", null, null, "meta_child")) {
+                assertThat(rs.next()).isTrue();
+                assertThat(rs.getString("PKTABLE_NAME")).isEqualTo("meta_parent");
+                assertThat(rs.getString("FKTABLE_NAME")).isEqualTo("meta_child");
+                assertThat(rs.next()).isFalse();
+            }
+
+            try (ResultSet rs = metadata.getTypeInfo()) {
+                List<String> typeNames = new ArrayList<>();
+                while (rs.next()) {
+                    typeNames.add(rs.getString("TYPE_NAME"));
+                }
+                assertThat(typeNames).containsExactly("NULL", "INTEGER", "REAL", "TEXT", "BLOB");
+            }
+        }
+    }
+
+    @Test
+    void keyMetadataWithoutForeignKeysIsEmptyAndWellFormed() throws SQLException {
+        try (Connection conn = DriverManager.getConnection(getDriverJdbcUrl())) {
+            try (Statement s = conn.createStatement()) {
+                s.execute("CREATE TABLE meta_plain (id INTEGER PRIMARY KEY, value TEXT)");
+            }
+            DatabaseMetaData metadata = conn.getMetaData();
+
+            try (ResultSet rs = metadata.getImportedKeys(null, null, "meta_plain")) {
+                assertThat(rs.getMetaData().getColumnCount()).isEqualTo(14);
+                assertThat(rs.next()).isFalse();
+            }
+            try (ResultSet rs = metadata.getExportedKeys(null, null, "meta_plain")) {
+                assertThat(rs.getMetaData().getColumnCount()).isEqualTo(14);
+                assertThat(rs.next()).isFalse();
+            }
+            try (ResultSet rs = metadata.getCrossReference(null, null, "meta_plain", null, null, "meta_plain")) {
+                assertThat(rs.getMetaData().getColumnCount()).isEqualTo(14);
+                assertThat(rs.next()).isFalse();
+            }
+            try (ResultSet rs = metadata.getPrimaryKeys(null, null, "meta_plain")) {
+                assertThat(rs.next()).isTrue();
+                assertThat(rs.getString("PK_NAME")).isNull();
+                assertThat(rs.next()).isFalse();
+            }
+        }
+    }
+}