Add GUC jsonb_partial_decompression

Author: Nikita Glukhov

src/backend/utils/adt/jsonb_util.c

@@ -134,6 +134,7 @@ static JsonbValue *fillCompressedJsonbValue(CompressedJsonb *cjb,
 											uint32 offset, JsonValue *result);
 static JsonbContainer *jsonbzDecompress(JsonContainer *jc);
 
+bool jsonb_partial_decompression = true;	/*GUC */
 
 JsonValue *
 JsonValueUnpackBinary(const JsonValue *jbv)
@@ -2654,7 +2655,8 @@ jsonbzIteratorInit(JsonContainer *jc)
 	Jsonb	   *jb = (Jsonb *) cjb->datum->data;
 	JsonbContainerHeader *jbc = (JsonbContainerHeader *)((char *) jb + cjb->offset);
 
-	//CompressedDatumDecompressAll(cjb->datum);
+	if (!jsonb_partial_decompression)
+		CompressedDatumDecompressAll(cjb->datum);
 
 	return jsonbIteratorInitExt(jc, jbc, cjb);
 }
@@ -2669,7 +2671,10 @@ jsonbzInit(JsonContainerData *jc, Datum value)
 	cjb->offset = offsetof(Jsonb, root);
 
 	CompressedDatumInit(cd, value);
-	CompressedDatumDecompress(cd, 256);
+	if (!jsonb_partial_decompression)
+		CompressedDatumDecompressAll(cd);
+	else
+		CompressedDatumDecompress(cd, 256);
 
 	jsonbzInitContainer(jc, cjb, VARSIZE_ANY_EXHDR(cd->data)); // cd->total_len - VARHDRSZ
 }

src/backend/utils/misc/guc.c

@@ -101,6 +101,7 @@
 #include "utils/bytea.h"
 #include "utils/float.h"
 #include "utils/guc_tables.h"
+#include "utils/jsonb.h"
 #include "utils/memutils.h"
 #include "utils/pg_locale.h"
 #include "utils/pg_lsn.h"
@@ -2182,6 +2183,15 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"jsonb_partial_decompression", PGC_USERSET, DEVELOPER_OPTIONS,
+			gettext_noop("Use partial pglz decompression for jsonb."),
+		},
+		&jsonb_partial_decompression,
+		true,
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL

src/include/utils/jsonb.h

@@ -250,4 +250,6 @@ extern Datum jsonb_build_object_worker(int nargs, Datum *args, bool *nulls,
 extern Datum jsonb_build_array_worker(int nargs, Datum *args, bool *nulls,
 									  Oid *types, bool absent_on_null);
 
+extern bool jsonb_partial_decompression;	/* GUC */
+
 #endif							/* __JSONB_H__ */