gh-64662: Add virtual table support to sqlite3.Connection.iterdump

[erlend-aasland]

• Issue: sqlite dumpiter dumps invalid script when virtual tables are used #64662

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📚 Documentation preview 📚: https://cpython-previews--108340.org.readthedocs.build/

[erlend-aasland]

@felixxm, would you like to review this? This is pretty much @palaviv's patch, adapted to main by me.

[erlend-aasland]

In businho/django-migrations-ci#38 (comment), @iurisilvio mentions that foreign key support must be disabled. ISTM that that aligns with the behaviour of the SQLite shell:

SQLite version 3.39.5 2022-10-14 20:58:05
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite> PRAGMA foreign_keys=ON;
sqlite> create virtual table test using fts4(example);
sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
PRAGMA writable_schema=ON;
INSERT INTO sqlite_schema(type,name,tbl_name,rootpage,sql)VALUES('table','test','test',0,'CREATE VIRTUAL TABLE test using fts4(example)');
CREATE TABLE IF NOT EXISTS 'test_content'(docid INTEGER PRIMARY KEY, 'c0example');
CREATE TABLE IF NOT EXISTS 'test_segments'(blockid INTEGER PRIMARY KEY, block BLOB);
CREATE TABLE IF NOT EXISTS 'test_segdir'(level INTEGER,idx INTEGER,start_block INTEGER,leaves_end_block INTEGER,end_block INTEGER,root BLOB,PRIMARY KEY(level, idx));
CREATE TABLE IF NOT EXISTS 'test_docsize'(docid INTEGER PRIMARY KEY, size BLOB);
CREATE TABLE IF NOT EXISTS 'test_stat'(id INTEGER PRIMARY KEY, value BLOB);
PRAGMA writable_schema=OFF;
COMMIT;
sqlite> ^D

[erlend-aasland]

Further experiments show that PRAGMA foreign_keys=OFF; is prepended no matter if virtual tables are involved or not, so we should fix that separately IMO.

[felixxm]

Maybe it's just me, but the number of different quotes in _iterdump() makes it hard for me to understand this code, check out #108472 (feel-free to reject it).

[erlend-aasland]

Thanks for the review, Mariusz!

[bedevere-bot]

GH-108563 is a backport of this pull request to the 3.12 branch.

[bedevere-bot]

GH-108564 is a backport of this pull request to the 3.11 branch.