Add support for `SET DEFAULT` and `DROP DEFAULT` statements #26162

ebyhr · 2025-07-10T01:40:54Z

Description

Add support for the following syntax:

    | ALTER TABLE (IF EXISTS)? tableName=qualifiedName
        ALTER COLUMN columnName=identifier SET DEFAULT literal         #setDefaultValue
    | ALTER TABLE (IF EXISTS)? tableName=qualifiedName
        ALTER COLUMN columnName=identifier DROP DEFAULT                #dropDefaultValue

DROP DEFAULT on columns that don't have defaults throws an exception because SQL spec states "The descriptor of C shall include a default value".

Release notes

## General, Memory
* Add support for `SET DEFAULT` and `DROP DEFAULT` statements. ({issue}`issuenumber`)

Praveen2112 · 2025-07-28T06:09:17Z

core/trino-main/src/main/java/io/trino/execution/DropDefaultValueTask.java

+        if (columnMetadata.isHidden()) {
+            throw semanticException(NOT_SUPPORTED, statement, "Cannot modify hidden column");
+        }
+        if (columnMetadata.getDefaultValue().isEmpty()) {
+            throw semanticException(NOT_SUPPORTED, statement, "Column '%s' does not have a default value", column);
+        }
+        metadata.dropDefaultValue(session, tableHandle, columnHandle);


Like we do for SetDefaultValueTask - can we also check if the Connector supports them out ?

Praveen2112 · 2025-07-28T06:16:57Z

core/trino-main/src/main/java/io/trino/execution/SetDefaultValueTask.java

+        if (redirectionAwareTableHandle.tableHandle().isEmpty()) {
+            String exceptionMessage = "Table '%s' does not exist".formatted(tableName);
+            if (metadata.getMaterializedView(session, tableName).isPresent()) {
+                exceptionMessage += ", but a materialized view with that name exists.";
+            }
+            else if (metadata.isView(session, tableName)) {
+                exceptionMessage += ", but a view with that name exists.";
+            }
+            if (!statement.isTableExists()) {
+                throw semanticException(TABLE_NOT_FOUND, statement, "%s", exceptionMessage);
+            }
+            return immediateVoidFuture();
+        }


Maybe as a follow-up - Do we need to abstract this out for all the DDL operations to be perfomed on a table ?

Praveen2112 · 2025-07-28T06:18:07Z

core/trino-grammar/src/main/antlr4/io/trino/grammar/sql/SqlBase.g4

+    | ALTER TABLE (IF EXISTS)? tableName=qualifiedName
+        ALTER COLUMN columnName=identifier SET DEFAULT literal         #setDefaultValue
+    | ALTER TABLE (IF EXISTS)? tableName=qualifiedName
+        ALTER COLUMN columnName=identifier DROP DEFAULT                #dropDefaultValue


Do we have any plans on setting the same for field as well ?

There is no plan about it as far as I know.

github-actions · 2025-08-26T17:03:13Z

This pull request has gone a while without any activity. Ask for help on #core-dev on Trino slack.

github-actions · 2025-09-17T17:03:22Z

This pull request has gone a while without any activity. Ask for help on #core-dev on Trino slack.

kasiafi

Reviewed.

By the way, I noticed that when we alter column type, we don't do any generic checks related to the default value. What does the spec say about it?

core/trino-grammar/src/main/antlr4/io/trino/grammar/sql/SqlBase.g4

core/trino-main/src/main/java/io/trino/execution/SetDefaultValueTask.java

core/trino-main/src/test/java/io/trino/execution/TestDropDefaultValueTask.java

core/trino-main/src/test/java/io/trino/execution/TestSetDefaultValueTask.java

core/trino-main/src/main/java/io/trino/execution/DropDefaultValueTask.java

ebyhr · 2025-10-05T00:50:27Z

The spec doesn't explicitly mention checking default values in 11.19 <alter column data type clause>, if I understand it correctly.

kasiafi

The spec doesn't explicitly mention checking default values in 11.19 , if I understand it correctly.

Right. Instead, the spec defines constraints on the new type based on the existing type. If those constraints are respected, then probably it guarantees that the default value remains valid.
However, we don't enforce these constraints in the engine, so the consistency here depends on the connector behavior.
@martint is this something we should revisit?

kasiafi · 2025-10-06T06:59:28Z

core/trino-main/src/main/java/io/trino/execution/DropDefaultValueTask.java

+            throw semanticException(NOT_SUPPORTED, statement, "Cannot modify hidden column");
+        }
+        if (columnMetadata.getDefaultValue().isEmpty()) {
+            throw semanticException(GENERIC_USER_ERROR, statement, "Column '%s' does not have a default value", columnName);


You can add a new error code for this case.

cla-bot bot added the cla-signed label Jul 10, 2025

github-actions bot added docs memory Memory connector labels Jul 10, 2025

ebyhr added the syntax-needs-review label Jul 10, 2025

ebyhr force-pushed the ebi/core-set-drop-default-clause branch 3 times, most recently from 5dce2c0 to 5f15ffb Compare July 10, 2025 05:18

ebyhr requested review from Praveen2112, kasiafi and martint July 10, 2025 06:53

ebyhr force-pushed the ebi/core-set-drop-default-clause branch 2 times, most recently from 71301fb to cb68fd6 Compare July 28, 2025 01:18

Praveen2112 approved these changes Jul 28, 2025

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ebyhr force-pushed the ebi/core-set-drop-default-clause branch from cb68fd6 to be71180 Compare August 5, 2025 04:39

github-actions bot added the stale label Aug 26, 2025

ebyhr force-pushed the ebi/core-set-drop-default-clause branch from be71180 to 223dff2 Compare August 26, 2025 21:43

github-actions bot removed the stale label Aug 27, 2025

github-actions bot added the stale label Sep 17, 2025

ebyhr force-pushed the ebi/core-set-drop-default-clause branch 3 times, most recently from 17bfa50 to d68f292 Compare September 18, 2025 13:48

github-actions bot removed the stale label Sep 18, 2025

kasiafi reviewed Sep 19, 2025

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ebyhr added 2 commits October 5, 2025 09:08

Support setting and dropping default column values in engine

439b914

Support setting and dropping default column values in Memory connector

e78ab36

ebyhr force-pushed the ebi/core-set-drop-default-clause branch from d68f292 to 4fc218e Compare October 5, 2025 00:31

github-actions bot added the lakehouse label Oct 5, 2025

ebyhr force-pushed the ebi/core-set-drop-default-clause branch from 4fc218e to e0de208 Compare October 5, 2025 00:43

fixup! Support setting and dropping default column values in engine

a9591b6

ebyhr force-pushed the ebi/core-set-drop-default-clause branch from e0de208 to a9591b6 Compare October 5, 2025 04:27

kasiafi approved these changes Oct 6, 2025

View reviewed changes

Add support for SET DEFAULT and DROP DEFAULT statements #26162

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ebyhr commented Jul 10, 2025

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Add support for `SET DEFAULT` and `DROP DEFAULT` statements #26162

Add support for `SET DEFAULT` and `DROP DEFAULT` statements #26162