Add support for NO_AUTO_VALUE_ON_ZERO SQL mode#366
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By default, MySQL treats a literal 0 in an AUTO_INCREMENT column the
same as NULL and generates the next sequence value. This behavior is
suppressed by the NO_AUTO_VALUE_ON_ZERO SQL mode, which is not part of
the default modes.
To emulate this on SQLite, rewrite the value to NULL via
NULLIF(CAST(... AS INTEGER), 0). The explicit CAST is required because
SQLite compares storage classes strictly, so NULLIF('0', 0) returns
'0', not NULL — and WordPress 1.0 emits the string form.
Also exclude AUTO_INCREMENT columns from the non-strict IMPLICIT
DEFAULT COALESCE wrapping, so a NULL (original or rewritten from 0)
always advances the sequence.
See: https://dev.mysql.com/doc/refman/8.4/en/sql-mode.html#sqlmode_no_auto_value_on_zero
JanJakes
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zaerl
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NO_AUTO_VALUE_ON_ZERO SQL mode
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Summary
Emulates MySQL's
NO_AUTO_VALUE_ON_ZEROSQL mode behavior on SQLite.MySQL treats a literal
0in anAUTO_INCREMENTcolumn the same asNULLand generates the next sequence value. This can be suppressed by theNO_AUTO_VALUE_ON_ZEROSQL mode, which is not part of MySQL's default modes.Some legacy WordPress versions rely on the default behavior — e.g. WP 1.0's
post.phpemits:On MySQL this stores
ID = 1. The current SQLite driver storedID = 0, which fails with legacy WP.Scope
INSERT/REPLACEvalue lists (includingVALUES,SET, andSELECTforms).UPDATE(and the UPDATE half ofINSERT ... ON DUPLICATE KEY UPDATE). MySQL never auto-generatesAUTO_INCREMENTvalues on UPDATE — zeros are stored literally.The default
sql_modewas already correct —NO_AUTO_VALUE_ON_ZEROis absent, matching MySQL 8.0 defaults.Tests
testDefaultSqlModeDoesNotIncludeNoAutoValueOnZero— asserts the default modes.testAutoIncrementZeroAdvancesSequenceByDefault—0,'0', andNULLall generate new ids.testAutoIncrementZeroAdvancesSequenceForAllInsertShapes— coversINSERT ... SET,INSERT ... SELECT, andREPLACE.testNoAutoValueOnZeroSqlMode— with the mode on, literal0is stored as-is; onlyNULLadvances the sequence.See: https://dev.mysql.com/doc/refman/8.4/en/sql-mode.html#sqlmode_no_auto_value_on_zero