From 6fe2bea08912a7c0837849108c385ef008d4355d Mon Sep 17 00:00:00 2001
From: Paul Trowbridge <paul@hptrow.me>
Date: Thu, 18 Jun 2026 23:04:59 -0400
Subject: [PATCH] feat: -b bulk copy into Postgres dest via COPY FROM STDIN
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Extends -b to Postgres destinations: stream the source ResultSet into PG with
COPY <dt> FROM STDIN (FORMAT csv) via the JDBC CopyManager, instead of batched
INSERTs. COPY is text-based so the server parses each field into the column
type — no per-type quoting needed. Every non-null value is CSV-quoted (so
empty string stays distinct from NULL, which is an empty unquoted field);
rows are flushed in 1000-row buffers with a 10k-row progress counter.

Validated DB2->PG: numeric precision (123.4567), jsonb, unicode, embedded
quotes, NULL vs empty-string all correct.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 jrunner/src/main/java/jrunner/jrunner.java | 45 ++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/jrunner/src/main/java/jrunner/jrunner.java b/jrunner/src/main/java/jrunner/jrunner.java
index 7abef0d..e4533a3 100644
--- a/jrunner/src/main/java/jrunner/jrunner.java
+++ b/jrunner/src/main/java/jrunner/jrunner.java
@@ -10,6 +10,9 @@ import com.microsoft.sqlserver.jdbc.SQLServerBulkCopy;
 import com.microsoft.sqlserver.jdbc.SQLServerBulkCopyOptions;
 import com.microsoft.sqlserver.jdbc.ISQLServerBulkData;
 import com.microsoft.sqlserver.jdbc.SQLServerException;
+import org.postgresql.PGConnection;
+import org.postgresql.copy.CopyManager;
+import org.postgresql.copy.CopyIn;
 
 public class jrunner {
    //static final String QUERY = "SELECT * from rlarp.osm LIMIT 100";
@@ -333,6 +336,48 @@ public class jrunner {
                 e.printStackTrace();
                 System.exit(0);
             }
+        } else if (bulk && dcu.toLowerCase().startsWith("jdbc:postgresql:")) {
+            //-------------------------------bulk copy (COPY, Postgres dest)--------------------------------------------
+            // Stream the source ResultSet into Postgres via COPY ... FROM STDIN.
+            // COPY is text-based: each field is sent as CSV text and the server
+            // parses it into the column type, so there's no per-type quoting.
+            // Non-null values are always CSV-quoted; NULL is an empty unquoted
+            // field; column order must match the dest (positional, as always).
+            System.out.println("------------bulk copy (COPY)------------------------------");
+            try {
+                CopyManager cm = ((PGConnection) dcon).getCopyAPI();
+                CopyIn cin = cm.copyIn("COPY " + dt + " FROM STDIN WITH (FORMAT csv)");
+                StringBuilder buf = new StringBuilder();
+                long rows = 0;
+                while (rs.next()) {
+                    for (int i = 1; i <= cols; i++) {
+                        if (i > 1) { buf.append(','); }
+                        String val = rs.getString(i);
+                        if (!rs.wasNull() && val != null) {
+                            if (trim) { val = val.trim(); }
+                            buf.append('"').append(val.replace("\"", "\"\"")).append('"');
+                        }
+                        // else: empty field -> NULL
+                    }
+                    buf.append('\n');
+                    rows++;
+                    if (rows % 1000 == 0) {
+                        byte[] b = buf.toString().getBytes(java.nio.charset.StandardCharsets.UTF_8);
+                        cin.writeToCopy(b, 0, b.length);
+                        buf.setLength(0);
+                        if (rows % 10000 == 0) { System.out.print("\r" + rows); System.out.flush(); }
+                    }
+                }
+                if (buf.length() > 0) {
+                    byte[] b = buf.toString().getBytes(java.nio.charset.StandardCharsets.UTF_8);
+                    cin.writeToCopy(b, 0, b.length);
+                }
+                cin.endCopy();
+                System.out.print("\r" + rows);
+            } catch (Exception e) {
+                e.printStackTrace();
+                System.exit(0);
+            }
         } else {
             System.out.println("------------row count-------------------------------------");
             //-------------------------------build & execute sql-------------------------------------------------------------