[PHP] Restart interrupted db-apply from the beginning

[adamziel]

A stopped db-apply now starts an unchanged, complete db.sql from the beginning on a new target connection.

Background

The old code continued after its saved statement number. That statement number did not say which MySQL changes were committed. The new connection also skipped the dump header which sets SQL mode, foreign-key checks, unique checks, and autocommit.

This change

Before the first target query, database-apply.json stores the SHA-256 of db.sql, the target database, URL replacements, table prefix, and host-specific plugin removals. A later process starts again only when those values still match. If they do not, the error explains that the target may have changed and tells the user to restore or reset it before aborting the apply.

Every restart opens a new connection and reads db.sql from the beginning, so the header runs again. MySQL applies also hold a lock in the target database. A new process waits if the old target session is still running a query.

Completion is saved before normal command state. If the process stops between those two writes, the next process repairs the command state without applying SQL again.

This is PR 3 of 5: #590 → #591 → #595 → #582 → #607.

Testing

The focused tests cover orderly stops, process death, changed SQL, changed targets and options, connection failure, the final state-write failure, and a target session which remains alive after the PHP process dies. The MySQL E2E also checks that SQL mode and foreign-key settings run on the new connection.

[github-actions]

Pull pipeline performance — large-directory

Site: large-directory · 2,000+ plus targeted file-transfer scenarios files · 10,000 posts · 25,000 postmeta · PHP 8.5.9

Stage	PR	trunk	Δ	Status	Details
playground-sqlite-db-pull	9.68 s	9.61 s	⚪ +78 ms (+0.8%)	✓	condition=db-pull in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=lexer native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=selected trunk: condition=db-pull in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=lexer native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=selected
playground-sqlite-db-apply	3.72 s	3.73 s	⚪ -18 ms (-0.5%)	✓	condition=db-apply to SQLite in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=parser native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=verified native_ast=WP_MySQL_Native_Parser_Node sqlite_driver_parser=verified trunk: condition=db-apply to SQLite in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=parser native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=verified native_ast=WP_MySQL_Native_Parser_Node sqlite_driver_parser=verified
Total	13.40 s	13.34 s	⚪ +59 ms (+0.4%)

_{Numbers carry runner noise; treat single-run deltas as directional, not authoritative.}

_{📈 Trunk performance history — commit-by-commit timeline.}

[adamziel]

Closing this draft. It is being replaced by a smaller target-database checkpoint stack.