Merge pull request yugabyte#50 from koordinates/include-unchanged-toast

Preserve unchanged toast values by default.

This commit introduces a behavior change since TOAST values will always be output from now on. If you want the previous behavior, add include-unchanged-toast=0.

sql/bytea.sql

@@ -18,5 +18,5 @@ INSERT INTO xpto (bincol) SELECT decode(string_agg(to_char(round(g.i * random())
 UPDATE xpto SET rand1 = 123.456 WHERE id = 1;
 DELETE FROM xpto WHERE id = 1;
 
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'pretty-print', '1', 'include-typmod', '0');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'pretty-print', '1', 'include-typmod', '0', 'include-unchanged-toast', '0');
 SELECT 'stop' FROM pg_drop_replication_slot('regression_slot');

sql/toast.sql

@@ -27,7 +27,11 @@ UPDATE xpto SET toasted_col1 = (SELECT string_agg(g.i::text, '') FROM generate_s
 
 UPDATE xpto SET rand1 = 123.456 WHERE id = 1;
 
-DELETE FROM xpto WHERE id = 1;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'pretty-print', '1', 'include-typmod', '0', 'include-unchanged-toast', '0');
 
+UPDATE xpto SET rand1 = 234.567 WHERE id = 1;
+
+-- include-unchanged-toast=1 is the default
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'pretty-print', '1', 'include-typmod', '0');
+
 SELECT 'stop' FROM pg_drop_replication_slot('regression_slot');

wal2json.c

@@ -39,6 +39,7 @@ typedef struct
 	bool		include_type_oids;	/* include data type oids */
 	bool		include_typmod;		/* include typmod in types */
 	bool		include_not_null;	/* include not-null constraints */
+	bool        include_unchanged_toast;  /* include unchanged TOAST field values in output */
 
 	bool		pretty_print;		/* pretty-print JSON? */
 	bool		write_in_chunks;	/* write in chunks? */
@@ -134,6 +135,7 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool is
 	data->write_in_chunks = false;
 	data->include_lsn = false;
 	data->include_not_null = false;
+	data->include_unchanged_toast = true;
 	data->filter_tables = NIL;
 
 	/* add all tables in all schemas by default */
@@ -336,6 +338,19 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool is
 				pfree(rawstr);
 			}
 		}
+		else if (strcmp(elem->defname, "include-unchanged-toast") == 0)
+		{
+			if (elem->arg == NULL)
+			{
+				elog(LOG, "include-unchanged-toast is null");
+				data->include_unchanged_toast = true;
+			}
+			else if (!parse_bool(strVal(elem->arg), &data->include_unchanged_toast))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
+							 strVal(elem->arg), elem->defname)));
+		}
 		else
 		{
 			ereport(ERROR,
@@ -598,10 +613,10 @@ tuple_to_stringinfo(LogicalDecodingContext *ctx, TupleDesc tupdesc, HeapTuple tu
 		if (isnull && replident)
 			continue;
 
-		/* XXX Unchanged TOAST Datum does not need to be output */
-		if (!isnull && typisvarlena && VARATT_IS_EXTERNAL_ONDISK(origval))
+		if (!isnull && typisvarlena && VARATT_IS_EXTERNAL_ONDISK(origval) && !(data->include_unchanged_toast))
 		{
-			elog(WARNING, "column \"%s\" has an unchanged TOAST", NameStr(attr->attname));
+			/* With include-unchanged-toast=0, unchanged TOAST Datum do not need to be output */
+			elog(DEBUG1, "column \"%s\" has an unchanged TOAST - excluding", NameStr(attr->attname));
 			continue;
 		}