Add GUC jsonb_partial_decompression

Author: Nikita Glukhov

src/backend/utils/adt/jsonb_util.c

@@ -159,7 +159,8 @@ static JsonbValue *fillCompressedJsonbValue(CompressedJsonb *cjb,
 											uint32 offset, JsonValue *result);
 static JsonbContainer *jsonbzDecompress(JsonContainer *jc);
 
-bool jsonb_sort_field_values = true;	/* GUC */
+bool jsonb_sort_field_values = true;		/* GUC */
+bool jsonb_partial_decompression = true;	/*GUC */
 
 JsonValue *
 JsonValueUnpackBinary(const JsonValue *jbv)
@@ -2573,7 +2574,6 @@ CompressedDatumDecompress(CompressedDatum *cd, Size offset)
 	cd->decompressed_len = offset;
 }
 
-#if 0 /* unused */
 static void
 CompressedDatumDecompressAll(CompressedDatum *cd)
 {
@@ -2588,7 +2588,6 @@ CompressedDatumDecompressAll(CompressedDatum *cd)
 		cd->decompressed_len = cd->total_len;
 	}
 }
-#endif
 
 static void
 jsonbzInitContainer(JsonContainerData *jc, CompressedJsonb *cjb, int len)
@@ -2844,7 +2843,8 @@ jsonbzIteratorInit(JsonContainer *jc)
 	Jsonb	   *jb = (Jsonb *) cjb->datum->data;
 	JsonbContainer *jbc = (JsonbContainer *)((char *) jb + cjb->offset);
 
-	//CompressedDatumDecompressAll(cjb->datum);
+	if (!jsonb_partial_decompression)
+		CompressedDatumDecompressAll(cjb->datum);
 
 	return jsonbIteratorInit(jc, jbc, cjb);
 }
@@ -2859,7 +2859,10 @@ 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

@@ -2046,6 +2046,16 @@ 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

@@ -413,6 +413,7 @@ extern void JsonbHashScalarValueExtended(const JsonbValue *scalarVal,
 extern int reserveFromBuffer(StringInfo buffer, int len);
 extern void appendToBuffer(StringInfo buffer, const void *data, int len);
 
-extern bool jsonb_sort_field_values;	/* GUC */
+extern bool jsonb_sort_field_values;		/* GUC */
+extern bool jsonb_partial_decompression;	/* GUC */
 
 #endif							/* __JSONB_H__ */