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expression: set a collation according to the arguments for ifnull in constant folding (#52119) #52131

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merged 2 commits into from
Apr 12, 2024
Merged

expression: set a collation according to the arguments for ifnull in constant folding (#52119) #52131

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3057eb3
This is an automated cherry-pick of #52119
YangKeao Mar 27, 2024
5cb4130
fix conflicts
YangKeao Apr 11, 2024
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10 changes: 9 additions & 1 deletion expression/constant_fold.go
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Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,15 @@ func ifNullFoldHandler(expr *ScalarFunction) (Expression, bool) {
// evaluated to constArg.Value after foldConstant(args[0]), it's not
// needed to be checked.
if constArg.Value.IsNull() {
return foldConstant(args[1])
foldedExpr, isConstant := foldConstant(args[1])

// See https://github.com/pingcap/tidb/issues/51765. If the first argument can
// be folded into NULL, the collation of IFNULL should be the same as the second
// arguments.
expr.GetType().SetCharset(args[1].GetType().GetCharset())
expr.GetType().SetCollate(args[1].GetType().GetCollate())

return foldedExpr, isConstant
}
return constArg, isDeferred
}
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20 changes: 20 additions & 0 deletions expression/integration_test/integration_test.go
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Expand Up @@ -8025,3 +8025,23 @@ func TestIssue50850(t *testing.T) {
testkit.Rows("01", "31", "34", "5D", "65", "A5", "A6", "B1", "D5", "FF"))
tk.MustExec("drop table if exists t3;")
}

func TestIssue51765(t *testing.T) {
store := testkit.CreateMockStore(t)

tk := testkit.NewTestKit(t, store)

tk.MustExec("use test")
tk.MustExec("create table t (id varbinary(16))")
tk.MustExec("create table t1(id char(16) charset utf8mb4 collate utf8mb4_general_ci)")
tk.MustExec("insert into t values ()")
tk.MustExec(`insert into t1 values ("Hello World")`)

tk.MustQuery("select collation(ifnull(concat(NULL), '~'))").Check(testkit.Rows("utf8mb4_bin"))
tk.MustQuery("select collation(ifnull(concat(NULL),ifnull(concat(NULL),'~')))").Check(testkit.Rows("utf8mb4_bin"))
tk.MustQuery("select collation(ifnull(concat(id),'~')) from t;").Check(testkit.Rows("binary"))
tk.MustQuery("select collation(ifnull(concat(NULL),ifnull(concat(id),'~'))) from t;").Check(testkit.Rows("binary"))
tk.MustQuery("select collation(ifnull(concat(id),ifnull(concat(id),'~'))) from t;").Check(testkit.Rows("binary"))
tk.MustQuery("select collation(ifnull(concat(NULL),id)) from t1;").Check(testkit.Rows("utf8mb4_general_ci"))
tk.MustQuery("select collation(ifnull(concat(NULL),ifnull(concat(NULL),id))) from t1;").Check(testkit.Rows("utf8mb4_general_ci"))
}