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schemadiff: more INSTANT algorithm considerations #16678

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merged 2 commits into from
Aug 29, 2024
Merged

schemadiff: more INSTANT algorithm considerations #16678

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facaf5d
schemadiff: INSTANT algorithm not supported for CHANGE COLUMN and MOD…
shlomi-noach Aug 29, 2024
cc7b217
handle no-default DATETIME
shlomi-noach Aug 29, 2024
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13 changes: 13 additions & 0 deletions go/vt/schemadiff/capability.go
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,13 @@ func alterOptionCapableOfInstantDDL(alterOption sqlparser.AlterOption, createTab
// Expression default values are not supported
return false, nil
}
if strings.EqualFold(column.Type.Type, "datetime") {
e := &ColumnDefinitionEntity{ColumnDefinition: column}
if !e.IsNullable() && !e.HasDefault() {
// DATETIME columns must have a default value
return false, nil
}
}
}
if opt.First || opt.After != nil {
// not a "last" column. Only supported as of 8.0.29
Expand Down Expand Up @@ -185,6 +192,9 @@ func alterOptionCapableOfInstantDDL(alterOption sqlparser.AlterOption, createTab
}
return capableOf(capabilities.InstantAddDropColumnFlavorCapability)
case *sqlparser.ChangeColumn:
if opt.First || opt.After != nil {
return false, nil
}
// We do not support INSTANT for renaming a column (ALTER TABLE ...CHANGE) because:
// 1. We discourage column rename
// 2. We do not produce CHANGE statements in declarative diff
Expand All @@ -198,6 +208,9 @@ func alterOptionCapableOfInstantDDL(alterOption sqlparser.AlterOption, createTab
}
return false, nil
case *sqlparser.ModifyColumn:
if opt.First || opt.After != nil {
return false, nil
}
if col := findColumn(opt.NewColDefinition.Name.String()); col != nil {
return changeModifyColumnCapableOfInstantDDL(col, opt.NewColDefinition)
}
Expand Down
44 changes: 43 additions & 1 deletion go/vt/schemadiff/capability_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,24 @@ func TestAlterTableCapableOfInstantDDL(t *testing.T) {
alter: "alter table t add column i2 int generated always as (i1 + 1) virtual",
expectCapableOfInstantDDL: true,
},
{
name: "add nullable datetime column",
create: "create table t(id int, i1 int not null, primary key(id))",
alter: "alter table t add column dt datetime(3)",
expectCapableOfInstantDDL: true,
},
{
name: "add default null datetime column",
create: "create table t(id int, i1 int not null, primary key(id))",
alter: "alter table t add column dt datetime(3) default null",
expectCapableOfInstantDDL: true,
},
{
name: "add datetime column without default",
create: "create table t(id int, i1 int not null, primary key(id))",
alter: "alter table t add column dt datetime(3) not null",
expectCapableOfInstantDDL: false,
},
{
name: "add stored column",
create: "create table t(id int, i1 int not null, primary key(id))",
Expand Down Expand Up @@ -225,11 +243,23 @@ func TestAlterTableCapableOfInstantDDL(t *testing.T) {
expectCapableOfInstantDDL: false,
},
{
name: "set column dfault value to null",
name: "set column default value to null",
create: "create table t(id int, i1 int, primary key(id))",
alter: "alter table t modify column i1 int default null",
expectCapableOfInstantDDL: true,
},
{
name: "rearrange column after",
create: "create table t(id int, i1 int, i2 int, primary key(id))",
alter: "alter table t modify column i1 int after i2",
expectCapableOfInstantDDL: false,
},
{
name: "rearrange column first",
create: "create table t(id int, i1 int, i2 int, primary key(id))",
alter: "alter table t modify column i1 int first",
expectCapableOfInstantDDL: false,
},
// enum/set:
{
name: "change enum default value",
Expand Down Expand Up @@ -291,6 +321,18 @@ func TestAlterTableCapableOfInstantDDL(t *testing.T) {
alter: "alter table t1 change column i1 i2 int visible",
expectCapableOfInstantDDL: false,
},
{
name: "change column, first",
create: "create table t1 (id int, i1 int, i2 int)",
alter: "alter table t1 change column i1 i1 int first",
expectCapableOfInstantDDL: false,
},
{
name: "change column, after",
create: "create table t1 (id int, i1 int, i2 int)",
alter: "alter table t1 change column i1 i1 int after i2",
expectCapableOfInstantDDL: false,
},
{
name: "make a column invisible via SET",
create: "create table t1 (id int, i1 int)",
Expand Down
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