dssysolyatin commented on code in PR #4572:
URL: https://github.com/apache/calcite/pull/4572#discussion_r2416247477
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core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java:
##########
@@ -1141,16 +1138,21 @@ public Result visit(TableModify modify) {
return result(sqlInsert, ImmutableList.of(), modify, null);
}
case UPDATE: {
+ final List<String> updateColumnList =
+ requireNonNull(modify.getUpdateColumnList(),
+ () -> "modify.getUpdateColumnList() is null for " + modify);
final Result input = visitInput(modify, 0);
+ final SqlSelect sourceSelect = input.asSelect();
Review Comment:
Let's assume we have this input expression:
```
UPDATE `foodmart`.`product` SET `product_name` = `product_name` || 'calcite'
WHERE `product_id` > 10
```
calcite parser will parse it as:
```
SqlUpdate(
targetColumnList = [product_name],
sourceExpressionList = [`product_name` || 'calcite'],
condition = `product_id` > 10,
sourceSelect = null <-- sourceSelect is null
)
```
Then, `ValidatorImpl.createSourceSelectForUpdate` changes it into:
```
SqlUpdate(
targetColumnList = [product_name],
sourceExpressionList = [`product_name` || 'calcite'],
condition = `product_id` > 10,
sourceSelect = "SELECT *, `product_name` || 'calcite' AS `EXPR$0` FROM
`foodmart`.`product` WHERE `product_id` > 10"
)
```
Next, `SqlToRelConverter` converts it into this logical plan:
```
LogicalTableModify(
table=[[foodmart, product]], operation=[UPDATE],
updateColumnList=[[product_name]],
sourceExpressionList=[[CAST(||($3, 'calcite')):VARCHAR(60) NOT NULL]],
flattened=[true]
)
LogicalProject(product_class_id=[$0], product_id=[$1], <all 14 fields>,
EXPR$0=[||($3, 'calcite')])
LogicalFilter(condition=[>($1, 10)])
LogicalTableScan(table=[[foodmart, product]])
```
`LogicalTableModify.sourceExpressionList` is built using the blackboard from
LogicalProject, but it doesn’t use expressions directly from `LogicalProject`.
(This is one more reason my previous fix was incorrect. It lost type coercion
in this case).
Now, answer on your question: "What is this SqlSelect node"
`RelToSqlConverter` transforms `TableModify.input` into:
```
SELECT `product_class_id`, `product_id`, `brand_name`, `product_name`,
`SKU`, `SRP`, `gross_weight`, `net_weight`, `recyclable_package`, `low_fat`,
`units_per_case`, `cases_per_pallet`, `shelf_width`, `shelf_height`,
`shelf_depth`, `product_name` || 'calcite' AS `EXPR$0`
FROM `foodmart`.`product`
WHERE `product_id` > 10
```
Calcite takes the WHERE clause for the UPDATE from this SELECT. ~(This is
not completely correct. if we later support `UPDATE FROM` syntax, it will be
wrong. Instead, we should build the `WHERE` clause based on the `SELECT`
context, rather than reusing parts of the `SELECT`)~
We also need to convert `TableModify.sourceExpressionList` into a `SqlNode`
using the context of this SELECT, similar to how we use the LogicalProject
blackboard when converting a SqlNode to a RelNode. My current fix uses this
approach
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