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feat: propagate GEOMETRY CRS as PostGIS SRID via EWKB #418

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feat: propagate GEOMETRY CRS as PostGIS SRID via EWKB #418

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41 changes: 40 additions & 1 deletion src/include/postgres_binary_writer.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@

#include "duckdb.hpp"
#include "duckdb/common/types/interval.hpp"
#include "duckdb/common/types/geometry_crs.hpp"
#include "duckdb/common/serializer/memory_stream.hpp"
#include "postgres_conversion.hpp"

Expand Down Expand Up @@ -207,6 +208,44 @@ class PostgresBinaryWriter {
stream.WriteData(const_data_ptr_cast(str_data), str_size);
}

//! Write GEOMETRY to PostGIS. If the type carries CRS metadata, writes EWKB
//! (WKB with SRID) so PostGIS receives the correct SRID.
void WriteGeometry(string_t value, const LogicalType &type) {
if (!type.AuxInfo()) {
WriteRawBlob(value);
return;
}
auto &crs = LogicalType::GetCRS(type);

// Extract SRID from CRS identifier (e.g., "EPSG:4326" → 4326)
auto &id = crs.GetIdentifier();
auto colon = id.find(':');
if (colon == string::npos) {
WriteRawBlob(value);
return;
}
int32_t srid;
try {
srid = std::stoi(id.substr(colon + 1));
} catch (...) {
WriteRawBlob(value);
return;
}

// Write EWKB: WKB with SRID flag set on the type field + 4-byte SRID inserted.
// [byte_order:1] [type|0x20000000:4] [srid:4] [coordinates...]
auto wkb_size = value.GetSize();
auto wkb_data = const_data_ptr_cast(value.GetData());
WriteRawInteger<int32_t>(NumericCast<int32_t>(wkb_size + 4));
stream.WriteData(wkb_data, 1); // byte order
uint32_t wkb_type;
memcpy(&wkb_type, wkb_data + 1, 4);
wkb_type |= 0x20000000;
stream.WriteData(const_data_ptr_cast(reinterpret_cast<const uint8_t *>(&wkb_type)), 4); // type + SRID flag
stream.WriteData(const_data_ptr_cast(reinterpret_cast<const uint8_t *>(&srid)), 4); // SRID (LE, matching WKB)
stream.WriteData(wkb_data + 5, wkb_size - 5); // rest of payload
}

void WriteVarchar(string_t value) {
auto str_size = value.GetSize();
auto str_data = value.GetData();
Expand Down Expand Up @@ -354,7 +393,7 @@ class PostgresBinaryWriter {
}
case LogicalTypeId::GEOMETRY: {
auto data = FlatVector::GetData<string_t>(col)[r];
WriteRawBlob(data);
WriteGeometry(data, type);
break;
}
case LogicalTypeId::ENUM: {
Expand Down
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