Add read-only support for PostgreSQL array columns by bilby91 · Pull Request #3402 · Azure/data-api-builder

bilby91 · 2026-03-30T04:01:16Z

Summary

Add read-only support for PostgreSQL array columns (int[], text[], boolean[], bigint[], etc.) which previously caused initialization failures
Array columns are exposed as GraphQL list types ([Int], [String], etc.) and returned as JSON arrays in REST/MCP responses
Array columns are marked read-only and excluded from create/update mutation inputs until write support is implemented

Changes

Core plumbing (database-agnostic):

ColumnDefinition: new IsArrayType and ElementSystemType properties
SqlMetadataProvider: detect array types (System.Array) during schema introspection
SchemaConverter: unwrap array element types and generate ListTypeNode for GraphQL fields
EdmModelBuilder: represent array columns as EdmCollectionTypeReference in OData model
TypeHelper: fallback handling for unresolved System.Array type

PostgreSQL-specific:

PostgreSqlMetadataProvider: override PopulateColumnDefinitionWithHasDefaultAndDbType to resolve element types from information_schema udt_name (_int4→int, _text→string, etc.)

Tests:

14 new unit tests (array→ListTypeNode generation, nullability, AutoGenerated directive, byte[] exclusion)
3 new PostgreSQL e2e tests (query by PK, null arrays, multi-row queries)
Test schema and config for array_type_table entity

Limitations

Read-only: mutations on array columns are blocked (marked as auto-generated/read-only)
No OData $filter: filtering on array columns is not supported (no OData array operators)
PostgreSQL only: other databases don't have native array types; generic plumbing is in place for future use
1D arrays only: multi-dimensional arrays are not tested/supported

Test plan

Unit tests pass (1325/1325, 0 failures)
PostgreSQL e2e tests pass (3/3 array tests, 711/711 non-preexisting PG tests)
CI pipeline validation (PostgreSQL Docker)

Copilot

Pull request overview

Adds read-only support for PostgreSQL array columns in DAB so schema introspection and runtime initialization no longer fail when encountering int[], text[], boolean[], bigint[], etc. The change threads array-awareness through metadata, GraphQL schema generation, and the EDM model while keeping arrays excluded from mutation inputs.

Changes:

Detect PostgreSQL array columns during metadata introspection, resolve array element CLR types, and mark array columns read-only.
Expose array columns as GraphQL list types and represent them as EDM collection properties.
Add/extend unit + PostgreSQL e2e test coverage plus schema/config updates for a new array_type_table test entity.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Config/DatabasePrimitives/DatabaseObject.cs	Extends `ColumnDefinition` with `IsArrayType`/`ElementSystemType` to carry array metadata.
src/Core/Services/MetadataProviders/SqlMetadataProvider.cs	Detects array-typed columns from provider schema and marks them read-only.
src/Core/Services/MetadataProviders/PostgreSqlMetadataProvider.cs	Resolves PostgreSQL array element types via `information_schema` (`udt_name`) and updates `ColumnDefinition`.
src/Service.GraphQLBuilder/Sql/SchemaConverter.cs	Generates GraphQL fields as `ListTypeNode` for array columns and adds array-aware system type mapping.
src/Core/Parsers/EdmModelBuilder.cs	Emits EDM collection properties for array columns to support OData model building.
src/Core/Services/TypeHelper.cs	Adds fallback handling for abstract `System.Array` in EDM primitive type mapping.
src/Service.Tests/GraphQLBuilder/Sql/SchemaConverterTests.cs	Adds unit tests for array→GraphQL list type generation, nullability, directives, and `byte[]` exclusion.
src/Service.Tests/SqlTests/GraphQLSupportedTypesTests/PostgreSqlGQLArrayTypesTests.cs	Adds PostgreSQL e2e GraphQL tests validating array values and null handling.
src/Service.Tests/DatabaseSchema-PostgreSql.sql	Adds `array_type_table` DDL + seed data for PostgreSQL integration tests.
src/Service.Tests/dab-config.PostgreSql.json	Adds `ArrayType` entity configuration (read-only permissions) for PostgreSQL test runs.
src/Service.Tests/UnitTests/SerializationDeserializationTests.cs	Updates serialization test expectations to account for added `ColumnDefinition` fields.

src/Service.Tests/SqlTests/GraphQLSupportedTypesTests/PostgreSqlGQLArrayTypesTests.cs

aaronburtle · 2026-03-31T15:29:34Z

/azp run

azure-pipelines · 2026-03-31T15:30:04Z

Azure Pipelines successfully started running 6 pipeline(s).

bilby91 · 2026-03-31T15:39:03Z

@aaronburtle Thanks for approving CI. I'll take a look at the failing tests and address them.

bilby91 · 2026-03-31T17:35:53Z

@aaronburtle I think fixes should be in place.

aaronburtle · 2026-03-31T18:46:01Z

/azp run

azure-pipelines · 2026-03-31T18:46:29Z

Azure Pipelines successfully started running 6 pipeline(s).

aaronburtle · 2026-03-31T20:00:28Z

src/Core/Services/MetadataProviders/PostgreSqlMetadataProvider.cs

+        /// PostgreSQL array types in information_schema use udt_name with a leading underscore
+        /// (e.g., _int4 for int[], _text for text[]).
+        /// </summary>
+        private static readonly Dictionary<string, Type> _pgArrayUdtToElementType = new(StringComparer.OrdinalIgnoreCase)


Should be able to add _json, _jsonb, and _money to this dictionary. Currently these types would work for requests, but will generate the wrong schema types

Make sense. Will verify they work with some new tests.

aaronburtle · 2026-03-31T20:13:31Z

Looks like we are missing tests on the REST side of things. Should add some simple tests to validate REST works with array types, eg. GET /api/ArrayType and GET /api/ArrayType/id/1

aaronburtle · 2026-03-31T20:22:16Z

src/Service.GraphQLBuilder/Queries/InputTypeBuilder.cs

            foreach (FieldDefinitionNode field in node.Fields)
            {
+                // Skip array/list type fields (e.g., PostgreSQL array columns) - they cannot be ordered.
+                if (field.Type.IsListType())


CosmosDB has support for list types, so we can't just broadly skip them here. This needs to be scoped to SQL array columns only without breaking Cosmos list filtering.

I believe this is why the CosmosDB pipeline is failing.

aaronburtle · 2026-03-31T20:25:20Z

The PG_SQL Integration test failures are from mismatched configs, need to add the new section to ConfigurationTests.TestReadingRuntimeConfigForPostgreSql.verified.txt

PostgreSQL array columns (int[], text[], boolean[], bigint[], etc.) were previously unsupported and caused initialization failures. This change adds read-only support so array columns are exposed as list types in GraphQL ([Int], [String], etc.) and as JSON arrays in REST responses. Array columns are marked read-only and excluded from mutation input types until write support is implemented. The implementation adds generic array plumbing in the shared SQL layers and PostgreSQL-specific element type resolution via information_schema udt_name mapping. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Add ArrayType entity to postgresql-commands.txt so CI's config generator includes it, and skip list-type fields in InputTypeBuilder filter/orderby generation to prevent array columns from being incorrectly processed. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Add _json, _jsonb, _money to PostgreSQL array type mapping dictionary - Add json[], jsonb[], money[] columns to array_type_table test schema - Add REST integration tests for array type endpoints (list, by PK, nulls) - Update GraphQL array tests to cover new array column types - Update PostgreSQL snapshot to include ArrayType entity Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bilby91 · 2026-03-31T22:14:27Z

I handle most of the stuff already. Need to replicate the Cosmos issue locally and get it fixed. Will update when I have that aspect ready.

bilby91 marked this pull request as ready for review March 30, 2026 04:03

Copilot AI review requested due to automatic review settings March 30, 2026 04:03

bilby91 requested review from Alekhya-Polavarapu, Aniruddh25, JerryNixon, RubenCerna2079, aaronburtle, anushakolan, rusamant, sourabh1007, souvikghosh04, stuartpa and vadeveka as code owners March 30, 2026 04:03

Copilot started reviewing on behalf of bilby91 March 30, 2026 04:04 View session

Copilot AI reviewed Mar 30, 2026

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bilby91 force-pushed the feature/postgresql-array-columns-readonly branch from 5bb9456 to 29833c7 Compare March 30, 2026 04:19

aaronburtle self-assigned this Mar 31, 2026

aaronburtle reviewed Mar 31, 2026

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bilby91 and others added 3 commits March 31, 2026 17:49

bilby91 force-pushed the feature/postgresql-array-columns-readonly branch from b9e3435 to 684ced5 Compare March 31, 2026 22:14

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bilby91 commented Mar 30, 2026

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aaronburtle commented Mar 31, 2026

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