Add implicit % to bridge TABLESAMPLE syntax

include/pgduckdb/pgduckdb_ruleutils.h

@@ -30,5 +30,8 @@ int pgduckdb_show_type(Const *constval, int original_showtype);
 bool pgduckdb_subscript_has_custom_alias(Plan *plan, List *rtable, Var *subscript_var, char *colname);
 SubscriptingRef *pgduckdb_strip_first_subscript(SubscriptingRef *sbsref, StringInfo buf);
 char *pgduckdb_write_row_refname(StringInfo buf, char *refname, bool is_top_level);
+bool is_system_sampling(const char *tsm_name, int num_args);
+bool is_bernoulli_sampling(const char *tsm_name, int num_args);
+void pgduckdb_add_tablesample_percent(const char *tsm_name, StringInfo buf, int num_args);
 
 extern bool processed_targetlist;

src/pgduckdb_ruleutils.cpp

@@ -1137,4 +1137,22 @@ pgduckdb_is_not_default_expr(Node *node, void *context) {
 	return expression_tree_walker(node, (bool (*)())((void *)pgduckdb_is_not_default_expr), context);
 #endif
 }
+
+bool
+is_system_sampling(const char *tsm_name, int num_args) {
+	return (pg_strcasecmp(tsm_name, "system") == 0) && (num_args == 1);
+}
+
+bool
+is_bernoulli_sampling(const char *tsm_name, int num_args) {
+	return (pg_strcasecmp(tsm_name, "bernoulli") == 0) && (num_args == 1);
+}
+
+void
+pgduckdb_add_tablesample_percent(const char *tsm_name, StringInfo buf, int num_args) {
+	if (!(is_system_sampling(tsm_name, num_args) || is_bernoulli_sampling(tsm_name, num_args))) {
+		return;
+	}
+	appendStringInfoChar(buf, '%');
+}
 }

src/vendor/pg_ruleutils_14.c

@@ -11448,6 +11448,10 @@ get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
 		if (nargs++ > 0)
 			appendStringInfoString(buf, ", ");
 		get_rule_expr((Node *) lfirst(l), context, false);
+		const char *tsm_name = generate_function_name(tablesample->tsmhandler, 1,
+											NIL, argtypes,
+											false, NULL, EXPR_KIND_NONE);
+		pgduckdb_add_tablesample_percent(tsm_name, buf, list_length(tablesample->args));
 	}
 	appendStringInfoChar(buf, ')');
 

src/vendor/pg_ruleutils_15.c

@@ -11650,6 +11650,10 @@ get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
 		if (nargs++ > 0)
 			appendStringInfoString(buf, ", ");
 		get_rule_expr((Node *) lfirst(l), context, false);
+		const char *tsm_name = generate_function_name(tablesample->tsmhandler, 1,
+											NIL, argtypes,
+											false, NULL, EXPR_KIND_NONE);
+		pgduckdb_add_tablesample_percent(tsm_name, buf, list_length(tablesample->args));
 	}
 	appendStringInfoChar(buf, ')');
 

src/vendor/pg_ruleutils_16.c

@@ -11859,6 +11859,10 @@ get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
 		if (nargs++ > 0)
 			appendStringInfoString(buf, ", ");
 		get_rule_expr((Node *) lfirst(l), context, false);
+		const char *tsm_name = generate_function_name(tablesample->tsmhandler, 1,
+											NIL, argtypes,
+											false, NULL, EXPR_KIND_NONE);
+		pgduckdb_add_tablesample_percent(tsm_name, buf, list_length(tablesample->args));
 	}
 	appendStringInfoChar(buf, ')');
 

src/vendor/pg_ruleutils_17.c

@@ -12517,6 +12517,10 @@ get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
 		if (nargs++ > 0)
 			appendStringInfoString(buf, ", ");
 		get_rule_expr((Node *) lfirst(l), context, false);
+		const char *tsm_name = generate_function_name(tablesample->tsmhandler, 1,
+											NIL, argtypes,
+											false, NULL, EXPR_KIND_NONE);
+		pgduckdb_add_tablesample_percent(tsm_name, buf, list_length(tablesample->args));
 	}
 	appendStringInfoChar(buf, ')');
 

test/regression/expected/tablesample.out

@@ -0,0 +1,43 @@
+SET duckdb.force_execution = true;
+CREATE TABLE t (a INT);
+INSERT INTO t SELECT i FROM generate_series(1, 10) AS i;
+SELECT * FROM t TABLESAMPLE SYSTEM (100);
+ a  
+----
+  1
+  2
+  3
+  4
+  5
+  6
+  7
+  8
+  9
+ 10
+(10 rows)
+
+SELECT * FROM t TABLESAMPLE BERNOULLI (100);
+ a  
+----
+  1
+  2
+  3
+  4
+  5
+  6
+  7
+  8
+  9
+ 10
+(10 rows)
+
+SELECT * FROM t TABLESAMPLE BERNOULLI (50) REPEATABLE(42);
+ a  
+----
+  2
+  5
+  7
+ 10
+(4 rows)
+
+DROP TABLE t;

test/regression/schedule

@@ -40,3 +40,4 @@ test: date
 test: timestamp_timestamptz
 test: union_functions
 test: foreign_data_wrapper
+test: tablesample

test/regression/sql/tablesample.sql

@@ -0,0 +1,11 @@
+SET duckdb.force_execution = true;
+
+CREATE TABLE t (a INT);
+INSERT INTO t SELECT i FROM generate_series(1, 10) AS i;
+
+SELECT * FROM t TABLESAMPLE SYSTEM (100);
+
+SELECT * FROM t TABLESAMPLE BERNOULLI (100);
+SELECT * FROM t TABLESAMPLE BERNOULLI (50) REPEATABLE(42);
+
+DROP TABLE t;