[#25044] YSQL: Ignore FREEZE option in COPY

Summary:
### Issue first observed in

```
./bin/pgbench  -i -s 10  -U yugabyte -h 127.0.0.1 -p 5433 yugabyte
dropping old tables...
NOTICE:  table "pgbench_accounts" does not exist, skipping
NOTICE:  table "pgbench_branches" does not exist, skipping
NOTICE:  table "pgbench_history" does not exist, skipping
NOTICE:  table "pgbench_tellers" does not exist, skipping
creating tables...
WARNING:  storage parameter fillfactor is unsupported, ignoring
WARNING:  storage parameter fillfactor is unsupported, ignoring
WARNING:  storage parameter fillfactor is unsupported, ignoring
generating data (client-side)...
1000000 of 1000000 tuples (100%) done (elapsed 0.45 s, remaining 0.00 s)
ERROR:  cannot perform COPY FREEZE because the table was not created or truncated in the current subtransaction
pgbench: error: PQendcopy failed
```

with read committed isolation level.

### Root Cause

pgbench fetches server version and uses COPY with FREEZE option if available

```name=pgbench.c
	/*
	 * accounts is big enough to be worth using COPY and tracking runtime
	 */
	/* use COPY with FREEZE on v14 and later without partitioning */
	if (partitions == 0 && PQserverVersion(con) >= 140000)
		copy_statement = "copy pgbench_accounts from stdin with (freeze on)";
	else
		copy_statement = "copy pgbench_accounts from stdin";
```

this triggers an assert condition because of our savepoint logic in read committed.

### Objective

DocDB does not support FREEZE. So, we introduce the following semantics with FREEZE on COPY FROM command

1. When yb_ignore_freeze_with_copy = true, display a NOTICE saying that FREEZE is unsupported.
2. When  yb_ignore_freeze_with_copy = false, raise an error.

```
dropping old tables...
NOTICE:  table "pgbench_accounts" does not exist, skipping
NOTICE:  table "pgbench_branches" does not exist, skipping
NOTICE:  table "pgbench_history" does not exist, skipping
NOTICE:  table "pgbench_tellers" does not exist, skipping
creating tables...
WARNING:  storage parameter fillfactor is unsupported, ignoring
WARNING:  storage parameter fillfactor is unsupported, ignoring
WARNING:  storage parameter fillfactor is unsupported, ignoring
generating data (client-side)...
1000000 of 1000000 tuples (100%) done (elapsed 0.52 s, remaining 0.00 s)
ERROR:  cannot perform COPY FREEZE on a YugaByte table
```

Ignore FREEZE with COPY FROM by default for pg compatibility.

Fixes #25044.
Jira: DB-14178

Test Plan:
Jenkins

Added a simple test to yb_feature_copy.sql.
```
./yb_build.sh --java-test TestPgRegressFeature
```

Reviewers: pjain, smishra

Reviewed By: pjain

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D40477

src/postgres/src/backend/commands/copyfrom.c

@@ -55,6 +55,7 @@
 
 /* Yugabyte includes */
 #include "executor/ybcModifyTable.h"
+#include "pg_yb_utils.h"
 #include "utils/builtins.h"
 
 /*
@@ -625,8 +626,10 @@ CopyFrom(CopyFromState cstate)
 	 * scan or command tolerates false negatives. FREEZE causes other sessions
 	 * to see rows they would not see under MVCC, and a false negative merely
 	 * spreads that anomaly to the current session.
+	 *
+	 * YB: We don't support COPY FREEZE on YB tables.
 	 */
-	if (cstate->opts.freeze)
+	if (!IsYugaByteEnabled() && cstate->opts.freeze)
 	{
 		/*
 		 * We currently disallow COPY FREEZE on partitioned tables.  The
@@ -667,6 +670,11 @@ CopyFrom(CopyFromState cstate)
 		ti_options |= TABLE_INSERT_FROZEN;
 	}
 
+	if (IsYugaByteEnabled() && cstate->opts.freeze)
+		ereport(yb_ignore_freeze_with_copy ? NOTICE : ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot perform COPY FREEZE on a YugaByte table")));
+
 	/*
 	 * We need a ResultRelInfo so we can use the regular executor's
 	 * index-entry-making machinery.  (There used to be a huge amount of code

src/postgres/src/backend/utils/misc/guc.c

@@ -3070,6 +3070,16 @@ static struct config_bool ConfigureNamesBool[] =
 		},
 		&yb_enable_advisory_locks,
 		false,
+	},
+
+	{
+		{"yb_ignore_freeze_with_copy", PGC_USERSET, ERROR_HANDLING_OPTIONS,
+			gettext_noop("Ignore the FREEZE flag on COPY FROM command."),
+			NULL,
+			GUC_NOT_IN_SAMPLE
+		},
+		&yb_ignore_freeze_with_copy,
+		true,
 		NULL, NULL, NULL
 	},
 

src/postgres/src/backend/utils/misc/pg_yb_utils.c

@@ -1591,6 +1591,7 @@ bool yb_enable_fkey_catcache = true;
 bool yb_enable_nop_alter_role_optimization = true;
 bool yb_enable_inplace_index_update = true;
 bool yb_enable_advisory_locks = false;
+bool yb_ignore_freeze_with_copy = true;
 
 YBUpdateOptimizationOptions yb_update_optimization_options = {
 	.has_infra = true,

src/postgres/src/include/pg_yb_utils.h

@@ -595,6 +595,11 @@ extern bool yb_enable_fkey_catcache;
  */
 extern bool yb_enable_nop_alter_role_optimization;
 
+/*
+ * Compatibility option to ignore FREEZE with COPY FROM.
+ */
+extern bool yb_ignore_freeze_with_copy;
+
 //------------------------------------------------------------------------------
 // GUC variables needed by YB via their YB pointers.
 extern int StatementTimeout;

src/postgres/src/test/regress/expected/yb_feature_copy.out

@@ -549,6 +549,20 @@ select * from main_table order by a;
  5 | 5
 (5 rows)
 
+-- FREEZE
+truncate copy_options;
+copy copy_options from stdin with (format csv, freeze);
+NOTICE:  cannot perform COPY FREEZE on a YugaByte table
+select * from copy_options order by a;
+ a | b
+---+---
+ 1 | 1
+ 2 | 2
+ 3 | 3
+ 4 | 4
+ 5 | 5
+(5 rows)
+
 -- clean up
 DROP TABLE forcetest;
 DROP TABLE x;

src/postgres/src/test/regress/sql/yb_feature_copy.sql

@@ -430,6 +430,18 @@ copy main_table from stdin with (format csv, disable_fk_check);
 
 select * from main_table order by a;
 
+-- FREEZE
+truncate copy_options;
+copy copy_options from stdin with (format csv, freeze);
+1,1
+2,2
+3,3
+4,4
+5,5
+\.
+
+select * from copy_options order by a;
+
 -- clean up
 DROP TABLE forcetest;
 DROP TABLE x;