From d1ac855d0b975001142624321d390f9b15493249 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Thu, 7 Nov 2024 12:28:52 +0100
Subject: [PATCH] CreateFieldFromArrowSchema(): take into account
 GDAL:OGR:Type=DataTime when ArrowSchema.format='u' (string)

---
 autotest/ogr/ogr_mem.py                   | 52 +++++++++++++++++++++++
 ogr/ogrsf_frmts/generic/ogrlayerarrow.cpp | 25 ++++++++++-
 2 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/autotest/ogr/ogr_mem.py b/autotest/ogr/ogr_mem.py
index c5918ea20085..aa0cbe9a521e 100755
--- a/autotest/ogr/ogr_mem.py
+++ b/autotest/ogr/ogr_mem.py
@@ -1022,6 +1022,58 @@ def test_ogr_mem_arrow_stream_numpy_datetime_as_string():
     assert batch["datetime"][3] == b"2022-05-31T12:34:56+12:30"
 
 
+###############################################################################
+# Test CreateFieldFromArrowSchema() when there is a GDAL:OGR:type=DateTime
+# Arrow schema metadata.
+
+
+@gdaltest.enable_exceptions()
+def test_ogr_mem_arrow_write_with_datetime_as_string():
+
+    src_ds = ogr.GetDriverByName("Memory").CreateDataSource("")
+    src_lyr = src_ds.CreateLayer("src_lyr", geom_type=ogr.wkbNone)
+
+    field = ogr.FieldDefn("dt", ogr.OFTDateTime)
+    src_lyr.CreateField(field)
+
+    f = ogr.Feature(src_lyr.GetLayerDefn())
+    src_lyr.CreateFeature(f)
+
+    f = ogr.Feature(src_lyr.GetLayerDefn())
+    f.SetField("dt", "2022-05-31T12:34:56.789Z")
+    src_lyr.CreateFeature(f)
+
+    f = ogr.Feature(src_lyr.GetLayerDefn())
+    f.SetField("dt", "2022-05-31T12:34:56")
+    src_lyr.CreateFeature(f)
+
+    f = ogr.Feature(src_lyr.GetLayerDefn())
+    f.SetField("dt", "2022-05-31T12:34:56+12:30")
+    src_lyr.CreateFeature(f)
+
+    ds = ogr.GetDriverByName("Memory").CreateDataSource("")
+    dst_lyr = ds.CreateLayer("dst_lyr")
+
+    stream = src_lyr.GetArrowStream(["DATETIME_AS_STRING=YES"])
+    schema = stream.GetSchema()
+
+    for i in range(schema.GetChildrenCount()):
+        dst_lyr.CreateFieldFromArrowSchema(schema.GetChild(i))
+
+    while True:
+        array = stream.GetNextRecordBatch()
+        if array is None:
+            break
+        dst_lyr.WriteArrowBatch(schema, array)
+
+    assert [f.GetField("dt") for f in dst_lyr] == [
+        None,
+        "2022/05/31 12:34:56.789+00",
+        "2022/05/31 12:34:56",
+        "2022/05/31 12:34:56+1230",
+    ]
+
+
 ###############################################################################
 
 
diff --git a/ogr/ogrsf_frmts/generic/ogrlayerarrow.cpp b/ogr/ogrsf_frmts/generic/ogrlayerarrow.cpp
index a0100c9ed738..2a999fd91a91 100644
--- a/ogr/ogrsf_frmts/generic/ogrlayerarrow.cpp
+++ b/ogr/ogrsf_frmts/generic/ogrlayerarrow.cpp
@@ -6160,7 +6160,23 @@ bool OGRLayer::CreateFieldFromArrowSchemaInternal(
             const auto oMetadata = OGRParseArrowMetadata(schema->metadata);
             for (const auto &oIter : oMetadata)
             {
-                if (oIter.first == MD_GDAL_OGR_ALTERNATIVE_NAME)
+                if (oIter.first == MD_GDAL_OGR_TYPE)
+                {
+                    const auto &osType = oIter.second;
+                    for (auto eType = OFTInteger; eType <= OFTMaxType;)
+                    {
+                        if (OGRFieldDefn::GetFieldTypeName(eType) == osType)
+                        {
+                            oFieldDefn.SetType(eType);
+                            break;
+                        }
+                        if (eType == OFTMaxType)
+                            break;
+                        else
+                            eType = static_cast<OGRFieldType>(eType + 1);
+                    }
+                }
+                else if (oIter.first == MD_GDAL_OGR_ALTERNATIVE_NAME)
                     oFieldDefn.SetAlternativeName(oIter.second.c_str());
                 else if (oIter.first == MD_GDAL_OGR_COMMENT)
                     oFieldDefn.SetComment(oIter.second);
@@ -6615,6 +6631,13 @@ static bool BuildOGRFieldInfo(
                         bTypeOK = true;
                         break;
                     }
+                    else if (eOGRType == OFTDateTime &&
+                             sType.eType == OFTString)
+                    {
+                        bFallbackTypesUsed = true;
+                        bTypeOK = true;
+                        break;
+                    }
                     else
                     {
                         CPLError(CE_Failure, CPLE_AppDefined,