fix(c/driver/postgresql): chunk large COPY payloads

PostgreSQL apparently has an internal limit - split up batches to
stay under that limit.  It doesn't care about message boundaries
in this mode, so we can chunk naively.

Fixes apache#1921.

c/driver/postgresql/statement.cc

@@ -20,6 +20,7 @@
 
 #include "statement.h"
 
+#include <algorithm>
 #include <array>
 #include <cassert>
 #include <cerrno>
@@ -571,6 +572,12 @@ struct BindStream {
 
   AdbcStatusCode ExecuteCopy(PGconn* conn, int64_t* rows_affected,
                              struct AdbcError* error) {
+    // https://github.com/apache/arrow-adbc/issues/1921: PostgreSQL has a max
+    // size for a single message that we need to respect (1 GiB - 1).  Since
+    // the buffer can be chunked up as much as we want, go for 512 MiB as our
+    // limit.
+    // https://github.com/postgres/postgres/blob/23c5a0e7d43bc925c6001538f04a458933a11fc1/src/common/stringinfo.c#L28
+    constexpr int64_t kMaxCopyBufferSize = 0x20000000;
     if (rows_affected) *rows_affected = 0;
 
     PostgresCopyStreamWriter writer;
@@ -606,10 +613,18 @@ struct BindStream {
       }
 
       ArrowBuffer buffer = writer.WriteBuffer();
-      if (PQputCopyData(conn, reinterpret_cast<char*>(buffer.data), buffer.size_bytes) <=
-          0) {
-        SetError(error, "Error writing tuple field data: %s", PQerrorMessage(conn));
-        return ADBC_STATUS_IO;
+      {
+        auto* data = reinterpret_cast<char*>(buffer.data);
+        int64_t remaining = buffer.size_bytes;
+        while (remaining > 0) {
+          int64_t to_write = std::min<int64_t>(remaining, kMaxCopyBufferSize);
+          if (PQputCopyData(conn, data, to_write) <= 0) {
+            SetError(error, "Error writing tuple field data: %s", PQerrorMessage(conn));
+            return ADBC_STATUS_IO;
+          }
+          remaining -= to_write;
+          data += to_write;
+        }
       }
 
       if (rows_affected) *rows_affected += array->length;

python/adbc_driver_postgresql/tests/test_dbapi.py

@@ -15,9 +15,11 @@
 # specific language governing permissions and limitations
 # under the License.
 
+import string
 from pathlib import Path
 from typing import Generator
 
+import numpy
 import pyarrow
 import pyarrow.dataset
 import pytest
@@ -410,3 +412,15 @@ def test_ingest_temporary(postgres: dbapi.Connection) -> None:
         assert cur.fetch_arrow_table() == temp2
         cur.execute("SELECT * FROM temporary")
         assert cur.fetch_arrow_table() == temp2
+
+
+def test_ingest_large(postgres: dbapi.Connection) -> None:
+    """Regression test for #1921."""
+    # More than 1 GiB of data in one batch
+    arr = pyarrow.array(numpy.random.randint(-100, 100, size=4_000_000))
+    batch = pyarrow.RecordBatch.from_pydict(
+        {char: arr for char in string.ascii_lowercase}
+    )
+    table = pyarrow.Table.from_batches([batch] * 4)
+    with postgres.cursor() as cur:
+        cur.adbc_ingest("test_ingest_large", table, mode="replace")