chore: refine the replica-setup-pg and its doc

devtools/replica-setup-pg/README.md

@@ -27,7 +27,7 @@ bash replica_setup.sh --pg_dump /path/to/pg_dump
 ## Example
 
 ```bash
-bash replica_setup.sh --pg_dump ../../backup.sql
+bash replica_setup.sh --pg_dump pg_dump.sql
 ```
 
-This command sets up MyDuck Server as a replica of the PostgreSQL instance running at `192.168.1.100` on port `3306` with the user `root` and password `mypassword`.
+This command sets up MyDuck Server as a replica of the PostgreSQL instance running at `192.168.1.100` on port `5432` with the user `root` and password `mypassword`.

devtools/replica-setup-pg/replica_setup.sh

@@ -62,13 +62,10 @@ if [[ -z $MYDUCK_DB ]]; then
     usage
 fi
 
-# Step 1: Check if psql exists, if not, install it
+# Step 1: Check if psql exists
 if ! command -v psql &> /dev/null; then
-    echo "psql not found, attempting to install..."
-    bash install_psql.sh
-    check_command "psql installation"
-else
-    echo "psql is already installed."
+    echo "Error: psql is not installed."
+    exit 1
 fi
 
 # Step 2: Check if replication has already been started
@@ -92,7 +89,7 @@ fi
 # Step 5: Load the existing data from pg_dump file
 if [[ -n "$PG_DUMP" ]]; then
     echo "Loading the snapshot from pg_dump to MyDuck Server..."
-    source snapshot.sh
+    source snapshot_dump.sh
     check_command "loading a snapshot from pg_dump"
 else
     echo "No pg_dump file specified. Skipping snapshot."

pgserver/connection_handler.go

@@ -1034,7 +1034,11 @@ func (h *ConnectionHandler) sendError(err error) {
 }
 
 // convertQuery takes the given Postgres query, and converts it as an ast.ConvertedQuery that will work with the handler.
-func (h *ConnectionHandler) convertQuery(query string) (ConvertedQuery, error) {
+func (h *ConnectionHandler) convertQuery(query string, modifiers ...QueryModifier) (ConvertedQuery, error) {
+	for _, modifier := range modifiers {
+		query = modifier(query)
+	}
+
 	parsable := true
 	stmts, err := parser.Parse(query)
 	if err != nil {

pgserver/duck_handler.go

@@ -638,6 +638,9 @@ func resultForOkIter(ctx *sql.Context, iter sql.RowIter) (*Result, error) {
 // resultForEmptyIter ensures that an expected empty iterator returns no rows.
 func resultForEmptyIter(ctx *sql.Context, iter sql.RowIter) (*Result, error) {
 	defer trace.StartRegion(ctx, "DuckHandler.resultForEmptyIter").End()
+	if iter == nil {
+		return &Result{Fields: nil}, nil
+	}
 	if _, err := iter.Next(ctx); err != io.EOF {
 		return nil, fmt.Errorf("result schema iterator returned more than zero rows")
 	}

pgserver/query_modifier.go

@@ -0,0 +1,22 @@
+package pgserver
+
+import "regexp"
+
+type QueryModifier func(string) string
+
+func NewQueryReplacer(regex string, replacement string) QueryModifier {
+	r := regexp.MustCompile(regex)
+	return func(query string) string {
+		return r.ReplaceAllString(query, replacement)
+	}
+
+}
+
+func NewQueryRemover(regex string) QueryModifier {
+	return NewQueryReplacer(regex, "")
+}
+
+var (
+	removeLocaleProvider = NewQueryRemover(`(?i)LOCALE_PROVIDER = [^ ;]*`)
+	removeLocale         = NewQueryRemover(`(?i)LOCALE = [^ ;]*`)
+)