fix: EXPOSED-1040 Support SELECT without FROM table clause - #2902
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Leonid Stashevsky (e5l)
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Pull request overview
Adds first-class support for “tableless” SELECT statements (i.e., SELECT 1 without an explicit FROM) across Exposed’s JDBC and R2DBC APIs, including convenience terminals for fetching a single projected value and documentation/tests to lock in the behavior.
Changes:
- Introduces top-level tableless
select(...)overloads (JDBC + R2DBC) backed byTable.Dual, plusselectValue(...)terminals. - Adds a generic
literal(value)helper inexposed-corefor wrapping common scalar Kotlin/Java values as SQL literals, plus tests. - Updates user documentation and changelog; refreshes SQL Server docker image tag used in dev/test infra.
Reviewed changes
Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| exposed-tests/src/test/kotlin/org/jetbrains/exposed/v1/tests/shared/types/LiteralOpTests.kt | New tests for literal(value) type resolution, decimal precision/scale, and unsupported types. |
| exposed-tests/src/test/kotlin/org/jetbrains/exposed/v1/tests/shared/dml/SelectExpressionTest.kt | New JDBC tests covering tableless selects, selectValue, set ops, derived table usage, and edge cases. |
| exposed-tests/src/test/kotlin/org/jetbrains/exposed/v1/tests/shared/dml/DualTableTest.kt | Removes old Table.Dual-focused test, superseded by tableless select tests. |
| exposed-r2dbc/src/main/kotlin/org/jetbrains/exposed/v1/r2dbc/Queries.kt | Adds tableless select(...) overloads and suspending selectValue(...) terminals for R2DBC. |
| exposed-r2dbc/api/exposed-r2dbc.api | Public API surface update for the new R2DBC query helpers. |
| exposed-r2dbc-tests/src/test/kotlin/org/jetbrains/exposed/v1/r2dbc/sql/tests/shared/dml/SelectExpressionTest.kt | New R2DBC tests validating tableless select and selectValue behavior. |
| exposed-r2dbc-tests/src/test/kotlin/org/jetbrains/exposed/v1/r2dbc/sql/tests/shared/dml/DualTableTest.kt | Removes old R2DBC Table.Dual test, superseded by tableless select tests. |
| exposed-jdbc/src/main/kotlin/org/jetbrains/exposed/v1/jdbc/Queries.kt | Adds tableless select(...) overloads and selectValue(...) terminals for JDBC. |
| exposed-jdbc/api/exposed-jdbc.api | Public API surface update for the new JDBC query helpers. |
| exposed-core/src/main/kotlin/org/jetbrains/exposed/v1/core/LiteralOp.kt | Adds literal(value) auto-resolver for common scalar types (+ UUID support). |
| exposed-core/src/main/kotlin/org/jetbrains/exposed/v1/core/BinaryLiteralColumnType.kt | Internal column type to render ByteArray literals using blob/hex formatting rules. |
| exposed-core/api/exposed-core.api | Public API surface update for the new literal(value) function. |
| documentation-website/Writerside/topics/DSL-Querying-data.topic | Adds a “Tableless SELECT queries” documentation chapter with examples and caveats. |
| CHANGELOG.md | Adds feature entry describing tableless select + selectValue + literal. |
| buildScripts/docker/docker-compose-sqlserver.yml | Updates SQL Server container image tag. |
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Leonid Stashevsky (e5l)
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Please also check failing tests on some db?
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👍 Minor comments to check. Please also rebase to fix refactoring merge conflict.
| * | ||
| * Some queries without a `FROM` clause are valid, such as `select(intLiteral(1))`. Others are not. For example, | ||
| * Others are not. For example, | ||
| * `select(MyTable.id)` is rejected by the database during execution because `MyTable` is not a query source. |
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Duplicate KDocs line
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| * ```kotlin | ||
| * val one = intLiteral(1) | ||
| * val status = stringLiteral("ready") | ||
| * val result = select(listOf(one, status)).single() | ||
| * ``` |
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Would be nice if KDocs was similar to the one for function above, stating what the SQL would be:
For instance
SELECT 1, 'ready'can be written as follows:
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| * ```kotlin | ||
| * val one = intLiteral(1) | ||
| * val status = stringLiteral("ready") | ||
| * val result = select(listOf(one, status)).single() | ||
| * ``` |
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Same comment as for same file in exposed-jdbc
| <chapter id="tableless-select-limitations"> | ||
| <title>Limitations</title> | ||
| <p> | ||
| A tableless <code>SELECT</code> have some database limitations: |
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Minor: 'have' -> 'has'
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Description
Introduce select expression which allows to use select statement without column set.
Type of Change
Please mark the relevant options with an "X":
Updates/remove existing public API methods:
Affected databases:
Checklist
Related Issues
EXPOSED-1040 Support SELECT without FROM table clause