ARROW-17326: [Go][FlightSQL] Add FlightSQL support for Go (apache#13828)

This implements initial support for FlightSQL in Golang and is sufficient to pass the flight_sql integration scenario.

As a follow-up in a subsequent PR i'll implement an equivalent example to the C++ SQLite example using Go.

Also closes apache#12496

Authored-by: Matt Topol <[email protected]>
Signed-off-by: Matt Topol <[email protected]>

dev/archery/archery/integration/runner.py

@@ -435,7 +435,7 @@ def run_all_tests(with_cpp=True, with_java=True, with_js=True,
         Scenario(
             "flight_sql",
             description="Ensure Flight SQL protocol is working as expected.",
-            skip={"Rust", "Go"}
+            skip={"Rust"}
         ),
     ]
 

format/Flight.proto

@@ -19,7 +19,7 @@
 syntax = "proto3";
 
 option java_package = "org.apache.arrow.flight.impl";
-option go_package = "github.com/apache/arrow/go/flight;flight";
+option go_package = "github.com/apache/arrow/go/arrow/flight/internal/flight";
 option csharp_namespace = "Apache.Arrow.Flight.Protocol";
 
 package arrow.flight.protocol;

format/FlightSql.proto

@@ -20,6 +20,7 @@ syntax = "proto3";
 import "google/protobuf/descriptor.proto";
 
 option java_package = "org.apache.arrow.flight.sql.impl";
+option go_package = "github.com/apache/arrow/go/arrow/flight/internal/flight";
 package arrow.flight.protocol.sql;
 
 /*

go/arrow/array/record.go

@@ -153,6 +153,10 @@ func NewRecord(schema *arrow.Schema, cols []arrow.Array, nrows int64) *simpleRec
 }
 
 func (rec *simpleRecord) validate() error {
+	if rec.rows == 0 && len(rec.arrs) == 0 {
+		return nil
+	}
+
 	if len(rec.arrs) != len(rec.schema.Fields()) {
 		return fmt.Errorf("arrow/array: number of columns/fields mismatch")
 	}

go/arrow/array/record_test.go

@@ -135,8 +135,7 @@ func TestRecord(t *testing.T) {
 		{
 			schema: schema,
 			cols:   nil,
-			rows:   -1,
-			err:    fmt.Errorf("arrow/array: number of columns/fields mismatch"),
+			rows:   0,			
 		},
 		{
 			schema: schema,

go/arrow/array/union.go

@@ -683,6 +683,10 @@ type UnionBuilder interface {
 	// Mode returns what kind of Union is being built, either arrow.SparseMode
 	// or arrow.DenseMode
 	Mode() arrow.UnionMode
+	// Child returns the builder for the requested child index.
+	// If an invalid index is requested (e.g. <0 or >len(children))
+	// then this will panic.
+	Child(idx int) Builder
 }
 
 type unionBuilder struct {
@@ -734,6 +738,13 @@ func newUnionBuilder(mem memory.Allocator, children []Builder, typ arrow.UnionTy
 	return b
 }
 
+func (b *unionBuilder) Child(idx int) Builder {
+	if idx < 0 || idx > len(b.children) {
+		panic("arrow/array: invalid child index for union builder")
+	}
+	return b.children[idx]
+}
+
 func (b *unionBuilder) Mode() arrow.UnionMode { return b.mode }
 
 func (b *unionBuilder) reserve(elements int, resize func(int)) {