feat: export via COPY TO STDOUT instead of temporary view (SUPPORT-17025)

[terezaskalova]

Summary

The Copy export adapter no longer creates a temporary view on the source database. Previously, when the DB user could create a view, each export ran DDL against the source:

CREATE TEMP VIEW "<uid>" AS <query>;
\COPY (SELECT * FROM "<uid>") TO '<file>' WITH CSV ...;
DROP VIEW "<uid>";

The temp view existed only to work around a psql limitation: the client-side \copy meta-command must fit on a single line, so multi-line queries fail unless wrapped in a view.

This PR switches to the server-side COPY (...) TO STDOUT SQL statement, redirecting its output to the target file with psql's \o meta-command:

\encoding UTF8
<initQueries>
\o '<file>'
COPY (<query>) TO STDOUT WITH CSV DELIMITER ',' FORCE QUOTE *;
\o

COPY ... TO STDOUT is a regular SQL statement, so it handles multi-line queries without any DDL and requires no special privileges (any user that can SELECT can run it). Output CSV is byte-for-byte the same as before.

Because no view is created anymore, the pre-flight canUserCreateView() (has_schema_privilege(...)) and isTransactionReadOnly() (SHOW transaction_read_only) probe queries — and the whole view/non-view branch — are removed. This also drops two round-trip queries per export.

This directly addresses the customer request in SUPPORT-17025 (replication with no DDL updates on the source).

Testing

• composer ci passes (phpcs, phpstan, unit + functional).
• Updated expected output for run-action-row-debug-logging (logged SQL) and error-invalid-query (error now references COPY (...) TO STDOUT instead of CREATE TEMP VIEW).
• run-action-with-read-only-user still passes, confirming read-only users export correctly via the new path.

Release Notes

Justification, description

Customer (SUPPORT-17025) requires DB replication with no DDL changes on the source. The Postgres extractor's Copy adapter created/dropped a temporary view per export; it now uses COPY (...) TO STDOUT redirected to the output file, avoiding all DDL while producing identical output.

Plans for Customer Communication

Provide the customer with a testing image tag to validate against their source before release.

Impact Analysis

Applies to all Postgres extractor exports using the Copy (psql) adapter. Output CSV is unchanged. Multi-line queries continue to work (previously handled via the temp view). Read-only users and users without CREATE privilege are unaffected (already used a direct COPY path).

Deployment Plan

Standard component release after review + CI.

Rollback Plan

Revert this PR / redeploy the previous image tag.

Post-Release Support Plan

Monitor extractor job error rates in Datadog for the Copy adapter.

Link to Devin session: https://app.devin.ai/sessions/66131de271cc4c3f98cda8411b9c4602
Requested by: @terezaskalova

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