From a1c9ea26ce13c6c76dd1a545a3af387e8fded368 Mon Sep 17 00:00:00 2001
From: Paul Trowbridge <paul@hptrow.me>
Date: Wed, 17 Jun 2026 15:37:47 -0400
Subject: [PATCH] fix: stream PostgreSQL source (migration mode) instead of
 buffering it all
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setFetchSize(10000) is a no-op on the PostgreSQL JDBC driver while autoCommit
is true — the driver loads the entire ResultSet into memory, OOM/GC-thrashing
on large source tables (a pg->SQL Server pull pinned the box: 4GB heap, swap
full, 0 rows written). PG only uses a server-side cursor when autoCommit is
false AND fetchSize > 0.

Set the source connection to manual commit ONLY in migration mode: the
migration source is read-only so never committing is harmless. Query mode is
excluded on purpose — callers (pipekit's run_dest_sql) run committed DDL/DML
through query mode, and autoCommit=false would roll those back on close.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 jrunner/src/main/java/jrunner/jrunner.java | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/jrunner/src/main/java/jrunner/jrunner.java b/jrunner/src/main/java/jrunner/jrunner.java
index 53a0a87..f786052 100644
--- a/jrunner/src/main/java/jrunner/jrunner.java
+++ b/jrunner/src/main/java/jrunner/jrunner.java
@@ -208,6 +208,15 @@ public class jrunner {
         }
         try {
             scon = DriverManager.getConnection(scu, scn, scp);
+            // Migration mode only: PostgreSQL ignores setFetchSize unless autoCommit
+            // is false — without this it buffers the ENTIRE result set into memory
+            // (OOM on big tables). The migration source is read-only, so never
+            // committing is harmless. Do NOT do this in query mode: callers run
+            // committed DDL/DML through query mode, and autoCommit=false would roll
+            // those statements back on connection close.
+            if (!queryMode) {
+                scon.setAutoCommit(false);
+            }
         } catch (SQLException e) {
             System.out.println("issue connecting to source:");
             e.printStackTrace();
@@ -303,6 +312,7 @@ public class jrunner {
                 for (int i = 1; i <= cols; i++){
                     switch (dtn[i].toUpperCase()){
                         case "VARCHAR":
+                        case "NVARCHAR":
                             nc = rs.getString(i);
                             if (rs.wasNull() || nc == null) {
                                 nc = "NULL";
@@ -313,6 +323,7 @@ public class jrunner {
                             nc = "'" + nc + "'";
                             break;
                         case "TEXT":
+                        case "NTEXT":
                             nc = rs.getString(i);
                             if (rs.wasNull() || nc == null) {
                                 nc = "NULL";
@@ -323,6 +334,7 @@ public class jrunner {
                             nc = "'" + nc + "'";
                             break;
                         case "CHAR":
+                        case "NCHAR":
                             nc = rs.getString(i);
                             if (rs.wasNull() || nc == null) {
                                 nc = "NULL";
@@ -333,6 +345,7 @@ public class jrunner {
                             nc = "'" + nc + "'";
                             break;
                         case "CLOB":
+                        case "NCLOB":
                             nc = rs.getString(i);
                             if (rs.wasNull() || nc == null) {
                                 nc = "NULL";