fix(tools): check for query execution error for pgxpool.Pool (#1969)

## Description

Return error if there's error during query execution. AlloyDB AI NL tool
was failing query silently. When this happened, the user was just
receiving `nil` response and not informed of what the error was.

## PR Checklist

> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:

- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
  before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
- [x] Make sure to add `!` if this involve a breaking change

🛠️ Fixes #1949

Author: Yuan325

internal/tools/alloydbainl/alloydbainl.go

@@ -179,6 +179,10 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		}
 		out = append(out, vMap)
 	}
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
 
 	return out, nil
 }

internal/tools/postgres/postgresdatabaseoverview/postgresdatabaseoverview.go

@@ -157,6 +157,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, rowMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslistactivequeries/postgreslistactivequeries.go

@@ -170,6 +170,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, rowMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslistavailableextensions/postgreslistavailableextensions.go

@@ -141,6 +141,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, vMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslistindexes/postgreslistindexes.go

@@ -192,6 +192,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, rowMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslistinstalledextensions/postgreslistinstalledextensions.go

@@ -152,6 +152,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, vMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslistschemas/postgreslistschemas.go

@@ -192,6 +192,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, rowMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslistsequences/postgreslistsequences.go

@@ -167,6 +167,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, rowMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslisttriggers/postgreslisttriggers.go

@@ -194,6 +194,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, rowMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }
 

internal/tools/postgres/postgreslistviews/postgreslistviews.go

@@ -159,6 +159,11 @@ func (t Tool) Invoke(ctx context.Context, params parameters.ParamValues, accessT
 		out = append(out, rowMap)
 	}
 
+	// this will catch actual query execution errors
+	if err := results.Err(); err != nil {
+		return nil, fmt.Errorf("unable to execute query: %w", err)
+	}
+
 	return out, nil
 }