Allow setting index_type (e.g., 'HASH' or 'BTREE')

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/Constraints.kt

@@ -163,7 +163,9 @@ data class Index(
     /** Whether the index in unique or not. */
     val unique: Boolean,
     /** Optional custom name for the index. */
-    val customName: String? = null
+    val customName: String? = null,
+    /** Optional custom index type (e.g, BTREE or HASH) */
+    val indexType: String? = null
 ) : DdlAware {
     /** Table where the index is defined. */
     val table: Table

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/Table.kt

@@ -877,9 +877,10 @@ open class Table(name: String = "") : ColumnSet(), DdlAware {
      * @param customIndexName Name of the index.
      * @param columns Columns that compose the index.
      * @param isUnique Whether the index is unique or not.
+     * @param indexType A custom index type (e.g., "BTREE" or "HASH").
      */
-    fun index(customIndexName: String? = null, isUnique: Boolean = false, vararg columns: Column<*>) {
-        _indices.add(Index(columns.toList(), isUnique, customIndexName))
+    fun index(customIndexName: String? = null, isUnique: Boolean = false, vararg columns: Column<*>, indexType: String? = null) {
+        _indices.add(Index(columns.toList(), isUnique, customIndexName, indexType = indexType))
     }
 
     /**

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/Default.kt

@@ -699,10 +699,15 @@ abstract class VendorDialect(
         val columnsList = index.columns.joinToString(prefix = "(", postfix = ")") { t.identity(it) }
         return if (index.unique) {
             "ALTER TABLE $quotedTableName ADD CONSTRAINT $quotedIndexName UNIQUE $columnsList"
+        } else if (index.indexType != null) {
+            return createIndexWithType(name = quotedIndexName, table = quotedTableName, columns = columnsList, type = index.indexType)
         } else {
             "CREATE INDEX $quotedIndexName ON $quotedTableName $columnsList"
         }
+    }
 
+    protected open fun createIndexWithType(name: String, table: String, columns: String, type: String): String {
+        return "CREATE INDEX $name ON $table $columns USING $type"
     }
 
     override fun dropIndex(tableName: String, indexName: String): String {

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/H2.kt

@@ -145,6 +145,10 @@ open class H2Dialect : VendorDialect(dialectName, H2DataTypeProvider, H2Function
             exposedLogger.warn("Index on ${index.table.tableName} for ${index.columns.joinToString { it.name }} can't be created in H2")
             return ""
         }
+        if (index.indexType != null) {
+            exposedLogger.warn("Index of type ${index.indexType} on ${index.table.tableName} for ${index.columns.joinToString { it.name }} can't be created in H2")
+            return ""
+        }
         return super.createIndex(index)
     }
 

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/MariaDBDialect.kt

@@ -1,9 +1,6 @@
 package org.jetbrains.exposed.sql.vendors
 
-import org.jetbrains.exposed.sql.Expression
-import org.jetbrains.exposed.sql.QueryBuilder
-import org.jetbrains.exposed.sql.Sequence
-import org.jetbrains.exposed.sql.append
+import org.jetbrains.exposed.sql.*
 
 internal object MariaDBFunctionProvider : MysqlFunctionProvider() {
     override fun nextVal(seq: Sequence, builder: QueryBuilder) = builder {

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/PostgreSQL.kt

@@ -223,6 +223,10 @@ open class PostgreSQLDialect : VendorDialect(dialectName, PostgreSQLDataTypeProv
 
     override fun setSchema(schema: Schema): String = "SET search_path TO ${schema.identifier}"
 
+    override fun createIndexWithType(name: String, table: String, columns: String, type: String): String {
+        return "CREATE INDEX $name ON $table USING $type $columns"
+    }
+
     companion object {
         /** PostgreSQL dialect name */
         const val dialectName: String = "postgresql"

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/SQLiteDialect.kt

@@ -137,6 +137,10 @@ open class SQLiteDialect : VendorDialect(dialectName, SQLiteDataTypeProvider, SQ
     override fun isAllowedAsColumnDefault(e: Expression<*>): Boolean = true
 
     override fun createIndex(index: Index): String {
+        if (index.indexType != null) {
+            exposedLogger.warn("Index of type ${index.indexType} on ${index.table.tableName} for ${index.columns.joinToString { it.name }} can't be created in SQLite")
+            return ""
+        }
         val originalCreateIndex = super.createIndex(index.copy(unique = false))
         return if (index.unique) {
             originalCreateIndex.replace("CREATE INDEX", "CREATE UNIQUE INDEX")

exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/ddl/CreateIndexTests.kt

@@ -0,0 +1,46 @@
+package org.jetbrains.exposed.sql.tests.shared.ddl
+
+import org.jetbrains.exposed.sql.SchemaUtils
+import org.jetbrains.exposed.sql.Table
+import org.jetbrains.exposed.sql.exists
+import org.jetbrains.exposed.sql.tests.DatabaseTestsBase
+import org.jetbrains.exposed.sql.tests.TestDB
+import org.jetbrains.exposed.sql.tests.shared.assertTrue
+import org.junit.Test
+
+class CreateIndexTests : DatabaseTestsBase() {
+
+    @Test
+    fun createStandardIndex() {
+        val TestTable = object : Table("test_table") {
+            val id = integer("id")
+            val name = varchar("name", length = 42)
+
+            override val primaryKey = PrimaryKey(id)
+            val byName = index("test_table_by_name", false, name)
+        }
+
+        withTables(excludeSettings = listOf(TestDB.H2_MYSQL), tables = *arrayOf(TestTable)) {
+            SchemaUtils.createMissingTablesAndColumns(TestTable)
+            assertTrue(TestTable.exists())
+            SchemaUtils.drop(TestTable)
+        }
+    }
+
+    @Test
+    fun createHashIndex() {
+        val TestTable = object : Table("test_table") {
+            val id = integer("id")
+            val name = varchar("name", length = 42)
+
+            override val primaryKey = PrimaryKey(id)
+            val byNameHash = index("test_table_by_name", /* isUnique = */ false, name, indexType = "HASH")
+        }
+
+        withTables(excludeSettings = listOf(TestDB.H2_MYSQL), tables = *arrayOf(TestTable)) {
+            SchemaUtils.createMissingTablesAndColumns(TestTable)
+            assertTrue(TestTable.exists())
+            SchemaUtils.drop(TestTable)
+        }
+    }
+}