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b9e781932d
Add a new sub-operation to the 'alter column' operation to drop `NOT
NULL` constraints from columns.
Currently, it is only possible to **set** `NOT NULL` constraints on
columns but not remove them. The syntax for doing this is:
```json
{
"name": "16_set_nullable",
"operations": [
{
"alter_column": {
"table": "reviews",
"column": "review",
"nullable": false,
"up": "(SELECT CASE WHEN review IS NULL THEN product || ' is good' ELSE review END)",
"down": "review"
}
}
]
}
```
Setting `nullable: true` in the above migration would result in a
validation error saying that removing `NOT NULL` constraints was not
supported. This PR removes this restriction and allows `nullable: true`
to remove an existing `NOT NULL` constraint.
A migration to remove a `NOT NULL` constraint looks like:
```json
{
"name": "31_unset_not_null",
"operations": [
{
"alter_column": {
"table": "posts",
"column": "title",
"nullable": true,
"up": "title",
"down": "(SELECT CASE WHEN title IS NULL THEN 'placeholder title' ELSE title END)"
}
}
]
}
```
The differences between adding and removing a `NOT NULL` constraint are:
* `nullable: true` vs `nullable: false`
* The roles of `up` and `down` SQL are reversed; `down` now needs to
rewrite any `NULL`s to meet the `NOT NULL` constraint on the old column.
`up` defaults to a simple copy of the data from the old column to the
new.
Fixes #223
15 lines
294 B
JSON
15 lines
294 B
JSON
{
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"name": "31_unset_not_null",
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"operations": [
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{
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"alter_column": {
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"table": "posts",
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"column": "title",
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"nullable": true,
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"up": "title",
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"down": "(SELECT CASE WHEN title IS NULL THEN 'placeholder title' ELSE title END)"
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}
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}
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]
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}
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