Treat missing PG extension/relation as skip, not failure

postgres.go

@@ -12,12 +12,33 @@ package main
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"io"
 	"os"
 	"path/filepath"
+
+	"github.com/jackc/pgx/v5/pgconn"
 )
 
+// isPGUnavailableError reports whether err indicates that the queried object
+// is not installed/available (missing extension, table, function, or schema).
+// These are treated as skips rather than failures.
+func isPGUnavailableError(err error) bool {
+	var pgErr *pgconn.PgError
+	if !errors.As(err, &pgErr) {
+		return false
+	}
+	switch pgErr.Code {
+	case "42P01", // undefined_table
+		"42704", // undefined_object
+		"42883", // undefined_function
+		"3F000": // invalid_schema_name
+		return true
+	}
+	return false
+}
+
 // postgresConfigFileTasks defines tasks for collecting PostgreSQL configuration files (sorted alphabetically by name)
 var postgresConfigFileTasks = []SimpleConfigFileTask{
 	{
@@ -154,6 +175,9 @@ func execPGQueryOnDB(dbname string, cfg *Config, query string, w io.Writer) erro
 
 	rows, err := db.Query(query)
 	if err != nil {
+		if isPGUnavailableError(err) {
+			return NewSkipError(err.Error())
+		}
 		return fmt.Errorf("query failed: %w", err)
 	}
 	defer closeErrCheck(rows, "query rows")

postgres_test.go

@@ -11,8 +11,13 @@
 package main
 
 import (
+	"bytes"
+	"errors"
 	"strings"
 	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/jackc/pgx/v5/pgconn"
 )
 
 // TestPostgreSQLCollectors verifies all expected PostgreSQL collectors are registered
@@ -151,3 +156,42 @@ func TestPostgreSQLTasksStructure(t *testing.T) {
 		}
 	}
 }
+
+// TestPGQueryCollectorUnavailableAsSkip verifies that PG errors for missing
+// extensions (undefined_table/function/object, invalid_schema) are returned
+// as SkipError, while real errors (permission denied) are returned as-is.
+func TestPGQueryCollectorUnavailableAsSkip(t *testing.T) {
+	tests := []struct {
+		name     string
+		pgErr    *pgconn.PgError
+		wantSkip bool
+	}{
+		{"undefined_table is skip", &pgconn.PgError{Code: "42P01", Message: "relation \"pg_stat_statements\" does not exist"}, true},
+		{"undefined_function is skip", &pgconn.PgError{Code: "42883", Message: "function does not exist"}, true},
+		{"undefined_object is skip", &pgconn.PgError{Code: "42704", Message: "type does not exist"}, true},
+		{"invalid_schema is skip", &pgconn.PgError{Code: "3F000", Message: "schema \"pgstatviz\" does not exist"}, true},
+		{"permission_denied is real error", &pgconn.PgError{Code: "42501", Message: "permission denied"}, false},
+		{"syntax_error is real error", &pgconn.PgError{Code: "42601", Message: "syntax error"}, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			db, mock, err := sqlmock.New()
+			if err != nil {
+				t.Fatalf("failed to create mock: %v", err)
+			}
+			mock.ExpectQuery("SELECT").WillReturnError(tt.pgErr)
+
+			collector := pgQueryCollector(db, "SELECT 1")
+			err = collector(&Config{}, &bytes.Buffer{})
+
+			if err == nil {
+				t.Fatal("expected error, got nil")
+			}
+			var skipErr SkipError
+			isSkip := errors.As(err, &skipErr)
+			if isSkip != tt.wantSkip {
+				t.Errorf("errors.As SkipError = %v, want %v (err: %v)", isSkip, tt.wantSkip, err)
+			}
+		})
+	}
+}

radar.go

@@ -614,6 +614,9 @@ func pgQueryCollector(db *sql.DB, query string) func(*Config, io.Writer) error {
 		}
 		rows, err := db.Query(query)
 		if err != nil {
+			if isPGUnavailableError(err) {
+				return NewSkipError(err.Error())
+			}
 			return err
 		}
 		defer closeErrCheck(rows, "query rows")