revert(dmat): revert dmat_string column wiring (#59681, #61036)

[fuziontech]

Problem

This reverts the dmat_string column wiring introduced in #59681 and the follow-up fix in #61036.

Changes

Reverts both PRs:

• fix(clickhouse): writable_events doesn't exist on DATA #61036 — fix(clickhouse): writable_events doesn't exist on DATA (a one-line fix to the 0267 migration)
• feat(dmat): re-apply dmat_string column wiring, scoped to data nodes #59681 — feat(dmat): re-apply dmat_string column wiring, scoped to data nodes

Net effect on master:

• Deletes the 0267_wire_up_existing_dmat_string_columns ClickHouse migration.
• Reverts the additions to posthog/models/event/sql.py (KAFKA_EVENTS_JSON_TABLE, EVENTS_JSON_MV, the DROP_* SQL constants, and the on_cluster parameter on KAFKA_EVENTS_TABLE_JSON_SQL).

max_migration.txt is intentionally left pointing at 0268_property_values_kafka_num_consumers — the latest migration, which landed after 0267 and is unrelated to this revert. Only the 0267 file is removed.

How did you test this code?

I'm an agent (Claude Code). No manual testing was performed. Verification done:

• Confirmed 0267 is the only migration file touched and that the newer 0268 migration (and max_migration.txt pointing at it) is preserved.
• Grepped the codebase to confirm no remaining references to the symbols removed from sql.py (DROP_KAFKA_EVENTS_JSON_TABLE_SQL, DROP_EVENTS_JSON_MV_SQL, KAFKA_EVENTS_JSON_TABLE, EVENTS_JSON_MV) outside the deleted migration — none remain.

🤖 Agent context

Authored by Claude Code on request to revert #61036 and #59681.

Approach: reverted the two squash-merge commits newest-first via git revert. The revert of #59681 conflicted on max_migration.txt because a later migration (0268) had already advanced the pointer past 0267; resolved by keeping 0268 rather than rolling the pointer back to 0266, so only the 0267 migration is removed and the unrelated 0268 migration stays intact.

[github-actions]

Hey @fuziontech! 👋

It looks like your git author email on this PR isn't your @posthog.com address (fuziontech@gmail.com). Since you're on the PostHog team, it's worth pointing your local git author email at your @posthog.com address. Why it matters:

• Consistent work identity in git history — internal tooling that attributes commits to team members keys off your @posthog.com address.
• Keeps team contributions easy to tell apart from external community ones when scanning history.

You can fix it for this repo with:

git config user.email "you@posthog.com"

Or set it globally with git config --global user.email "you@posthog.com". No need to redo this PR — just a nudge for next time. 🙂

[greptile-apps]

_{Reviews (1): Last reviewed commit: "Revert "feat(dmat): re-apply dmat_string..." | Re-trigger Greptile}

[Copilot]

Pull request overview

This PR reverts the dmat_string ClickHouse “wiring” that was previously added for the events ingestion pipeline, including removing the migration that recreated Kafka/MV tables and altered schemas to project dmat_string_* columns.

Changes:

• Deletes the ClickHouse migration 0267_wire_up_existing_dmat_string_columns, undoing the schema-wiring steps it introduced.
• Reverts posthog/models/event/sql.py additions by removing the JSON-table/MV name + DROP SQL constants and by removing the on_cluster toggle from KAFKA_EVENTS_TABLE_JSON_SQL.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
posthog/models/event/sql.py	Removes constants and restores KAFKA_EVENTS_TABLE_JSON_SQL to a no-arg form that always uses the default ON_CLUSTER_CLAUSE() behavior.
posthog/clickhouse/migrations/0267_wire_up_existing_dmat_string_columns.py	Deletes the migration that performed the dmat_string pipeline/schema wiring.

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[github-actions]

🎭 Playwright report

⚠️ 2 flaky tests:

• create experiment via wizard, add metrics, and launch (chromium)
• Split a person with multiple distinct IDs (chromium)

These issues are not necessarily caused by your changes.
Annoyed by this comment? Help fix flakies and failures and it'll disappear!

[deployment-status-posthog]

Deploy status

Environment	Status	Deployed At	Workflow
dev	✅ Deployed	2026-06-02 00:27 UTC	Run
prod-us	✅ Deployed	2026-06-02 10:18 UTC	Run
prod-eu	✅ Deployed	2026-06-02 10:20 UTC	Run