add nameconst#24887
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第一参数 name：
- 必须是 literal constant。
- 不能是 NULL。
- 可以是字符串 literal，也可以是数字 literal，最终用于生成结果列名。
- 不能引用表字段。
- 不能是函数、CAST(...)、表达式、子查询等。
第二参数 value：
- 必须是 literal constant。
- 支持各种 literal 类型：整数、uint64 边界值、decimal、float/double、字符串、NULL 等。
- 支持负数字面量，例如 -1、-12.34。
- 不支持列引用。
- 不支持函数调用。
- 不支持 CAST(...)。
- 不支持即使可 constant fold 的表达式，例如 abs(-1)。
合法例子：
select name_const('myname', 14);
select name_const(123, -456);
select name_const('x', 18446744073709551615);
select name_const('x', 'abc');
select name_const('x', null);
select name_const('x', -12.34);
非法例子：
select name_const(null, 1);
select name_const(a, 1) from t;
select name_const('x', a) from t;
select name_const('x', cast(14 as signed));
select name_const('x', abs(-1));
select name_const('x', now());
核心点：NAME_CONST 不是普通可折叠表达式函数。它更接近 MySQL 的行为，只接受 literal 形态的参数；第二参数虽然类型可以比较宽，但表达式形态必须受限，不能先通过 constant fold 把函数或 cast 伪装成 literal。
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aunjgr
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aunjgr
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MySQL NAME_CONST(name, value) — internal function used by replication. Returns value with column heading name.
Implementation:
foldNameConstArgsvalidates first arg is a non-null literal (column name), constant-folds the second arg (value)validNameConstValueExprallows literals, decimal-literal casts, and-literalforms- Binder integration at
bindFuncExprAndConstFoldcase"name_const"— constant-folds before proceeding - BVT covers single/multi-row, NULL args, JOIN, subquery, negative values, and error cases
Clean, matches MySQL 8.0 semantics. LGTM.
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XuPeng-SH
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XuPeng-SH
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I found two blocking issues in the NAME_CONST implementation.
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pkg/sql/plan/base_binder.go:1449-1567routesname_consttogoto between_fallbackwhenproc == nil. That fallback is BETWEEN-specific and unconditionally readsfnArgs[2], but NAME_CONST only has two arguments, so any nil-proc binder/internal path will panic with an index-out-of-range. -
pkg/sql/plan/query_builder.go:4482-4492only extracts the heading when the first argument is a bare*tree.NumVal, whilepkg/sql/plan/base_binder.go:2978-2991explicitly accepts parenthesized names by stripping*tree.ParenExpr. Soselect name_const(('myname'), (14))is accepted, but the column heading falls back toname_const(...)instead ofmyname.
…rixone into 0603-add-nameconst
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What type of PR is this?
Which issue(s) this PR fixes:
issue ##24486
What this PR does / why we need it:
增加name_const函数