fix: safely handle schema expansion on prepared statements with results

src/main/java/com/google/cloud/spanner/pgadapter/metadata/DescribeResult.java

@@ -20,6 +20,7 @@
 import com.google.cloud.spanner.pgadapter.error.PGExceptionFactory;
 import com.google.cloud.spanner.pgadapter.error.SQLState;
 import com.google.cloud.spanner.pgadapter.parsers.Parser;
+import com.google.common.base.Preconditions;
 import com.google.spanner.v1.StructType;
 import java.util.Arrays;
 import javax.annotation.Nullable;
@@ -31,6 +32,10 @@ public class DescribeResult {
   @Nullable private final Type columns;
   private final int[] parameters;
 
+  public static DescribeResult of(int[] givenParameterTypes, @Nullable Type columns) {
+    return new DescribeResult(givenParameterTypes, columns);
+  }
+
   public DescribeResult(int[] givenParameterTypes, @Nullable ResultSet resultMetadata) {
     this(
         givenParameterTypes,
@@ -40,11 +45,15 @@ public DescribeResult(int[] givenParameterTypes, @Nullable ResultSet resultMetad
         resultMetadata == null ? null : resultMetadata.getType());
   }
 
+  private DescribeResult(int[] givenParameterTypes, @Nullable Type columns) {
+    this(givenParameterTypes, null, columns);
+  }
+
   private DescribeResult(
       int[] givenParameterTypes,
       @Nullable StructType undeclaredParameters,
       @Nullable Type columns) {
-    this.givenParameterTypes = givenParameterTypes;
+    this.givenParameterTypes = Preconditions.checkNotNull(givenParameterTypes);
     this.undeclaredParameters = undeclaredParameters;
     this.parameters = extractParameters(givenParameterTypes, undeclaredParameters);
     this.columns = columns;

src/main/java/com/google/cloud/spanner/pgadapter/statements/IntermediatePortalStatement.java

@@ -65,10 +65,12 @@ public IntermediatePreparedStatement getPreparedStatement() {
   }
 
   public short getParameterFormatCode(int index) {
-    if (this.parameterFormatCodes.length == 0) {
+    if (this.parameterFormatCodes == null || this.parameterFormatCodes.length == 0) {
       return 0;
-    } else if (index >= this.parameterFormatCodes.length) {
+    } else if (this.parameterFormatCodes.length == 1) {
       return this.parameterFormatCodes[0];
+    } else if (index < 0 || index >= this.parameterFormatCodes.length) {
+      return 0;
     } else {
       return this.parameterFormatCodes[index];
     }
@@ -80,6 +82,8 @@ public short getResultFormatCode(int index) {
       return super.getResultFormatCode(index);
     } else if (this.resultFormatCodes.length == 1) {
       return this.resultFormatCodes[0];
+    } else if (index < 0 || index >= this.resultFormatCodes.length) {
+      return super.getResultFormatCode(index);
     } else {
       return this.resultFormatCodes[index];
     }

src/main/java/com/google/cloud/spanner/pgadapter/statements/IntermediatePreparedStatement.java

@@ -144,7 +144,7 @@ public Future<StatementResult> describeAsync(BackendConnection backendConnection
                     new DescribeResult(this.givenParameterDataTypes, result.getResultSet());
                 result.getResultSet().close();
               } else {
-                describeResult = new DescribeResult(this.givenParameterDataTypes, null);
+                describeResult = DescribeResult.of(this.givenParameterDataTypes, null);
               }
               return describeResult;
             },
@@ -158,7 +158,7 @@ public DescribeResult describe() {
     if (this.describeResult == null) {
       // Just return a DescribeResult that contains whatever information we were given in the
       // PARSE message.
-      return new DescribeResult(this.givenParameterDataTypes, null);
+      return DescribeResult.of(this.givenParameterDataTypes, null);
     }
     try {
       return this.describeResult.get();