Fix expression defaults being quoted as string literals#695
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…as string literals The schema differ was incorrectly quoting expression defaults like json_object() and json_array() as string literals (e.g. DEFAULT 'json_object()') instead of wrapping them in parentheses (DEFAULT (json_object())). This caused MySQL to reject the generated ALTER with errno 1101: "BLOB, TEXT, GEOMETRY or JSON column can't have a default value". Root cause: the Column struct had no way to distinguish expression defaults from literal defaults. The needsQuotes() function treated all unrecognized values (including function calls) as strings that needed quoting. The fix adds a DefaultIsExpr field to Column, set during parsing by inspecting the TiDB AST. Expression defaults are now formatted as DEFAULT (expr) while literal defaults continue to be quoted as DEFAULT 'value'. Also fixes parseExpression stripping trailing () from all zero-arg functions -- now only strips for timestamp-family functions (current_timestamp, now, etc.) where MySQL's canonical form omits the parens. Fixes #542 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Signed-off-by: Armand Parajon <armand@squareup.com>
…ing table Simulates the real-world scenario where a JSON column with DEFAULT (json_object()) is added to a table that already has multiple columns including other JSON columns. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Signed-off-by: Armand Parajon <armand@squareup.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Signed-off-by: Armand Parajon <armand@squareup.com>
morgo
approved these changes
Apr 20, 2026
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What's this?
Fixes expression defaults like
json_object(),json_array(), anduuid()being incorrectly quoted as string literals in generated ALTER statements.Before:
ALTER TABLE t1 ADD COLUMN metadata json NOT NULL DEFAULT 'json_object()'(errno 1101)After:
ALTER TABLE t1 ADD COLUMN metadata json NOT NULL DEFAULT (json_object())How it works
DefaultIsExprbool to theColumnstruct to track whether a default is an expression vs literalFuncCallExprnodes (json_object, json_array, uuid, etc.) are flagged as expression defaultsformatColumnDefinitionusesDEFAULT (expr)for expression defaults instead ofDEFAULT 'expr'parseExpressionstripping()from all zero-arg functions — now only strips for timestamp-family functions where MySQL's canonical form omits parensMost of this was written by Claude Code — I just provided direction.