From aadc47956edea63776c2d4466d6c3ee0557c0e43 Mon Sep 17 00:00:00 2001
From: Paul Oliver <contact@pauloliver.dev>
Date: Wed, 26 Nov 2025 02:20:36 +0100
Subject: Enable SQLite Write-Ahead Logging (WAL)

---
 core.j2.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

(limited to 'core.j2.c')

diff --git a/core.j2.c b/core.j2.c
index 45cd8b8..bd4b266 100644
--- a/core.j2.c
+++ b/core.j2.c
@@ -609,6 +609,31 @@ void salis_auto_save() {
 }
 {% endif %}
 
+{% if data_push_path is defined %}
+void salis_exec_sql(const char *sql) {
+    assert(sql);
+
+    int   sql_res;
+    char *sql_err;
+
+    while ((sql_res = sqlite3_exec(g_sim_data, sql, NULL, NULL, &sql_err)) == SQLITE_BUSY) {
+        g_warn("SQLite database returned error '%d' with message:", sql_res);
+        g_warn(sql_err);
+        sqlite3_free(sql_err);
+
+        switch (sql_res) {
+        case SQLITE_BUSY:
+            // Only handle busy database errors
+            g_info("Will retry query...");
+            continue;
+        default:
+            // Application should fail on all other error conditions
+            assert(false);
+        }
+    }
+}
+{% endif %}
+
 {% if args.command in ["bench", "new"] %}
 void salis_init() {
     assert(g_info);
@@ -631,6 +656,11 @@ void salis_init() {
     // Install busy handler to retry transactions if DB is locked
     sqlite3_busy_timeout(g_sim_data, {{ data_push_busy_timeout }});
 
+    // Enable Write-Ahead Logging (WAL)
+    // This seems to help prevent DB locks when displaying live data
+    // See: https://sqlite.org/wal.html
+    salis_exec_sql("pragma journal_mode=wal;");
+
     arch_push_data_header();
     arch_push_data_line();
     {% endif %}
-- 
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