Test saving bigStringColumn to Arrow

Author: Kopilov

dataframe-arrow/src/test/kotlin/org/jetbrains/kotlinx/dataframe/io/ArrowKtTest.kt

@@ -266,4 +266,11 @@ internal class ArrowKtTest {
             Locale.setDefault(currentLocale)
         }
     }
+
+    @Test
+    fun testBigStringColumn() {
+        val dataFrame = dataFrameOf(bigStringColumn)
+        val data = dataFrame.saveArrowFeatherToByteArray()
+        DataFrame.readArrowFeather(data) shouldBe dataFrame
+    }
 }

dataframe-arrow/src/test/kotlin/org/jetbrains/kotlinx/dataframe/io/examplesToWrite.kt

@@ -154,3 +154,39 @@ val citiesExampleSchema = """{
   } ]
 }
 """.trimIndent()
+
+/**
+ * String column (variable length vector) with size >1 MiB
+ */
+val bigStringColumn = run {
+    val list = ArrayList<String>()
+    for (i in 0 until 1024) {
+        val row = StringBuilder()
+        for (j in 0 until 64) {
+            row.append("abcd")
+        }
+        list.add(row.toString())
+    }
+    for (i in 0 until 1024) {
+        val row = StringBuilder()
+        for (j in 0 until 64) {
+            row.append("гдёж")
+        }
+        list.add(row.toString())
+    }
+    for (i in 0 until 1024) {
+        val row = StringBuilder()
+        for (j in 0 until 64) {
+            row.append("αβγδ")
+        }
+        list.add(row.toString())
+    }
+    for (i in 0 until 1024) {
+        val row = StringBuilder()
+        for (j in 0 until 64) {
+            row.append("正体字")
+        }
+        list.add(row.toString())
+    }
+    DataColumn.createValueColumn("bigStringColumn", list)
+}