I use the JSON extension to provide changelog-like functionality.

I just updated my local sqlite repo, as I tend to track closely to try and catch issues early (running 342af5b4fa0bd7c699e5497161db13d0cf795c7a). I am seeing the following when using some triggers that rely on Json functions:

Runtime error: out of memory (7)                                             

Here is the example that is failing for me in a test-case:

CREATE TABLE IF NOT EXISTS "person" (
  "id" INTEGER NOT NULL PRIMARY KEY, 
  "name" TEXT NOT NULL,
  "dob" DATE NOT NULL);
CREATE TABLE IF NOT EXISTS "changelog" (
  "id" INTEGER NOT NULL PRIMARY KEY,
  "timestamp" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
  "action" TEXT NOT NULL,
  "table" TEXT NOT NULL,
  "primary_key" INTEGER NOT NULL,
  "changes" JSON NOT NULL);
                                
CREATE TRIGGER IF NOT EXISTS person_changes_INSERT
AFTER INSERT ON person
BEGIN        
INSERT INTO changelog
  ("action", "table", "primary_key", "changes")
SELECT 'INSERT', 'person', NEW."id", "changes"
FROM (
SELECT json_group_object(
  col,
  json_array(
	case when json_valid("oldval") then json("oldval") else "oldval" end,
	case when json_valid("newval") then json("newval") else "newval" end)
  ) AS "changes"
    FROM (
  SELECT json_extract(value, '$[0]') as "col",
	 json_extract(value, '$[1]') as "oldval",
	 json_extract(value, '$[2]') as "newval"
  FROM json_each(json_array(
	json_array('name', NULL, NEW."name"),
	json_array('dob', NULL, NEW."dob")))
  WHERE "oldval" IS NOT "newval"
));
END;

INSERT INTO "person" ("name", "dob") VALUES ('Somebody', '2000-01-01');

Note I had to de-dent all the trigger code before running it interactively via the shell, since the shell seemed to try to do some autocomplete and threw a parse error. I have left it indented in the hopes this will help with readability.

The jist of the trigger is it is building a json object of changes from the previous data -> inserted data, and then storing the json object representing the changes in a changelog table.