fix: EXPOSED-701 [Oracle] Insert into table using only database default values fails

Oracle currently generates a statement like `INSERT ... DEFAULT VALUES` if an insert
operation is performed with no provided column set. This fails because that syntax
is not supported.

This switches to the `INSERT ... VALUES(DEFAULT, ...)` syntax instead and includes
a test for this case.

Author: bog-walk

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

@@ -367,6 +367,22 @@ internal object OracleFunctionProvider : FunctionProvider() {
         }
     }
 
+    override fun insert(
+        ignore: Boolean,
+        table: Table,
+        columns: List<Column<*>>,
+        expr: String,
+        transaction: Transaction
+    ): String {
+        val def = super.insert(ignore, table, columns, expr, transaction)
+        return if (def.endsWith(" $DEFAULT_VALUE_EXPRESSION")) {
+            val oracleDefaults = "VALUES(DEFAULT${", DEFAULT".repeat(table.columns.lastIndex)})"
+            "${def.removeSuffix(DEFAULT_VALUE_EXPRESSION)}$oracleDefaults"
+        } else {
+            def
+        }
+    }
+
     override fun explain(
         analyze: Boolean,
         options: String?,

exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/dml/InsertTests.kt

@@ -8,6 +8,8 @@ import org.jetbrains.exposed.dao.id.IdTable
 import org.jetbrains.exposed.dao.id.IntIdTable
 import org.jetbrains.exposed.sql.*
 import org.jetbrains.exposed.sql.SqlExpressionBuilder.eq
+import org.jetbrains.exposed.sql.SqlExpressionBuilder.isNull
+import org.jetbrains.exposed.sql.SqlExpressionBuilder.like
 import org.jetbrains.exposed.sql.kotlin.datetime.CurrentTimestamp
 import org.jetbrains.exposed.sql.kotlin.datetime.timestamp
 import org.jetbrains.exposed.sql.statements.BatchInsertStatement
@@ -788,4 +790,24 @@ class InsertTests : DatabaseTestsBase() {
             }
         }
     }
+
+    @Test
+    fun testInsertOfDefaultValuesOnly() {
+        val defaultAmount = 101
+        val defaultLabel = "none"
+        val defaultsOnlyTable = object : Table("defaults_only") {
+            val amount = integer("amount").default(defaultAmount)
+            val label = varchar("label", 32).default(defaultLabel)
+            val active = bool("active").nullable()
+        }
+
+        withTables(defaultsOnlyTable) {
+            defaultsOnlyTable.insert { }
+
+            val defaultsOnlyInserted = (defaultsOnlyTable.amount eq defaultAmount) and
+                (defaultsOnlyTable.label like defaultLabel) and
+                defaultsOnlyTable.active.isNull()
+            assertEquals(1, defaultsOnlyTable.selectAll().where { defaultsOnlyInserted }.count())
+        }
+    }
 }