Fix from-proto Postgres empty array insertion

[maoueh]

Root cause: PostgreSQL cannot determine the type of an empty array literal (array[]) without an explicit type cast. ClickHouse can infer the type from the column definition.

Fix implemented:

1. Added TypedEmptyArray struct in db_proto/sql/dialect.go to carry SQL type information for empty arrays
2. Added CreateEmptyArray method to Dialect interface that dialects implement to create appropriate empty array values
3. PostgreSQL implementation (db_proto/sql/postgres/dialect.go):
   • Returns a TypedEmptyArray with the SQL type (e.g., VARCHAR(255)[], INTEGER[])
4. ClickHouse implementation (db_proto/sql/click_house/dialect.go):
   • Returns plain []interface{}{} since ClickHouse infers types from schema
5. Updated ValueToString in db_proto/sql/postgres/types.go to handle TypedEmptyArray by generating array[]::TYPE
6. Updated database.go to use dialect.CreateEmptyArray(fd, column) instead of []interface{}{} for empty repeated fields

Test updates:

• Fixed entityTypesTestWithEmptyRepeatedString to set OptionalStr_2Uint256 (separate pre-existing issue with empty strings in NUMERIC columns)
• Fixed time comparison in PostgreSQL test to use time.Equal() instead of deep equality (timezone location differences)

[Copilot]

Pull request overview

This PR fixes a PostgreSQL-specific issue where inserting rows with empty repeated (array) fields in from-proto mode fails with "cannot determine type of empty array". The fix introduces a dialect-specific approach using a TypedEmptyArray struct that carries SQL type information, allowing PostgreSQL to generate explicit type casts (array[]::TYPE) while ClickHouse continues using plain empty arrays.

Changes:

• Added TypedEmptyArray struct and CreateEmptyArray method to the Dialect interface for database-specific empty array handling
• PostgreSQL dialect generates typed empty arrays with explicit casts, while ClickHouse uses plain empty slices
• Added integration tests for both PostgreSQL and ClickHouse to verify empty array handling, plus a UTC time fix for consistent test comparisons

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
db_proto/sql/dialect.go	Defines TypedEmptyArray struct and adds CreateEmptyArray method to the Dialect interface
db_proto/sql/postgres/dialect.go	Implements CreateEmptyArray to return typed empty arrays with SQL type information
db_proto/sql/postgres/types.go	Adds handling for TypedEmptyArray in ValueToString to generate array[]::TYPE syntax
db_proto/sql/click_house/dialect.go	Implements CreateEmptyArray to return plain empty slices (ClickHouse infers types from schema)
db_proto/sql/database.go	Updates empty array handling to use dialect.CreateEmptyArray() instead of hardcoded []interface{}{}
db_proto/sql/schema/table.go	Adds ColumnByFieldName helper method to look up columns by protobuf field name
tests/integration/db_proto_postgres_test.go	New integration test file for PostgreSQL empty array handling
tests/integration/db_proto_clickhouse_test.go	Adds test case for ClickHouse empty array handling and shared test helper function
tests/integration/helpers_test.go	Adds .UTC() to blockTime for consistent timezone handling in tests
CHANGELOG.md	Documents the PostgreSQL empty array fix

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[Copilot]

The MapFieldType function is called with a potentially nil column parameter. This could cause a nil pointer dereference at line 58 where it accesses column.Nested and at line 83 where it accesses column.ConvertTo.

While the current test passes because the column is found in typical use cases, the code should defensively handle nil column to prevent panics in edge cases where the column cannot be found (e.g., when tableInfo is nil or when the field is not registered in the table).

Consider adding a nil check at the beginning of CreateEmptyArray or in MapFieldType to handle this case gracefully.

Suggested change

	func (d *DialectPostgres) CreateEmptyArray(fd protoreflect.FieldDescriptor, column *schema.Column) any {
	func (d *DialectPostgres) CreateEmptyArray(fd protoreflect.FieldDescriptor, column *schema.Column) any {
	if column == nil {
	// Defensive check: avoid panicking in MapFieldType when column is unexpectedly nil.
	// Use a safe default SQL type ("text") in this edge case.
	zap.L().Warn("CreateEmptyArray called with nil column, using default SQL type 'text'",
	zap.String("field", string(fd.FullName())),
	)
	return sql2.TypedEmptyArray{SQLType: "text"}
	}