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Implement `Start` for **add column** operations that add a `NOT NULL` column without a `DEFAULT`. To add such a column without forcing a exclusive lock while a full table scan is performed, these steps need to be followed: On `Start`: 1. Add the new column 2. Add a `CHECK IS NOT NULL` constraint to the new column, but with `NOT VALID`, to avoid the scan. 3. Backfill the new column with the provided `up` SQL. On `Complete` 1. Validate the constraint (with `ALTER TABLE VALIDATE CONSTRAINT`). 2. Add the `NOT NULL` attribute to the column. The presence of a valid `NOT NULL` constraint on the column means that adding `NOT NULL` to the column does not perform a full table scan. See [this post](https://medium.com/paypal-tech/postgresql-at-scale-database-schema-changes-without-downtime-20d3749ed680#00dc) for a summary of these steps.
39 lines
730 B
JSON
39 lines
730 B
JSON
{
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"name": "03_add_column_to_products",
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"operations": [
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{
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"add_column": {
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"table": "products",
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"up": "UPPER(name)",
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"column": {
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"name": "description",
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"type": "varchar(255)",
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"nullable": true
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}
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}
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},
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{
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"add_column": {
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"table": "products",
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"column": {
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"name": "stock",
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"type": "int",
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"nullable": false,
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"default": "100"
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}
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}
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},
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{
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"add_column": {
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"table": "products",
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"up": "name || '-category'",
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"column": {
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"name": "category",
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"type": "varchar(255)",
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"nullable": false
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}
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}
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}
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]
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}
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