diff options
| -rw-r--r-- | src/backend/access/heap/tuptoaster.c | 94 |
1 files changed, 65 insertions, 29 deletions
diff --git a/src/backend/access/heap/tuptoaster.c b/src/backend/access/heap/tuptoaster.c index 05952bc80e8..2787611dd01 100644 --- a/src/backend/access/heap/tuptoaster.c +++ b/src/backend/access/heap/tuptoaster.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.12 2000/08/04 04:16:07 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.13 2000/10/23 23:42:04 tgl Exp $ * * * INTERFACE ROUTINES @@ -247,6 +247,11 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) /* ---------- * Then collect information about the values given + * + * NOTE: toast_action[i] can have these values: + * ' ' default handling + * 'p' already processed --- don't touch it + * 'x' incompressible, but OK to move off * ---------- */ memset(toast_action, ' ', numAttrs * sizeof(char)); @@ -397,6 +402,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) int biggest_attno = -1; int32 biggest_size = MAXALIGN(sizeof(varattrib)); Datum old_value; + Datum new_value; /* ---------- * Search for the biggest yet uncompressed internal attribute @@ -404,7 +410,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) */ for (i = 0; i < numAttrs; i++) { - if (toast_action[i] == 'p') + if (toast_action[i] != ' ') continue; if (VARATT_IS_EXTENDED(toast_values[i])) continue; @@ -421,20 +427,29 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) break; /* ---------- - * Compress it inline + * Attempt to compress it inline * ---------- */ i = biggest_attno; old_value = toast_values[i]; + new_value = toast_compress_datum(old_value); - toast_values[i] = toast_compress_datum(toast_values[i]); - if (toast_free[i]) - pfree(DatumGetPointer(old_value)); - toast_free[i] = true; - toast_sizes[i] = VARATT_SIZE(toast_values[i]); - - need_change = true; - need_free = true; + if (DatumGetPointer(new_value) != NULL) + { + /* successful compression */ + if (toast_free[i]) + pfree(DatumGetPointer(old_value)); + toast_values[i] = new_value; + toast_free[i] = true; + toast_sizes[i] = VARATT_SIZE(toast_values[i]); + need_change = true; + need_free = true; + } + else + { + /* incompressible data, ignore on subsequent compression passes */ + toast_action[i] = 'x'; + } } /* ---------- @@ -504,6 +519,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) int biggest_attno = -1; int32 biggest_size = MAXALIGN(sizeof(varattrib)); Datum old_value; + Datum new_value; /* ---------- * Search for the biggest yet uncompressed internal attribute @@ -511,7 +527,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) */ for (i = 0; i < numAttrs; i++) { - if (toast_action[i] == 'p') + if (toast_action[i] != ' ') continue; if (VARATT_IS_EXTENDED(toast_values[i])) continue; @@ -528,22 +544,29 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) break; /* ---------- - * Compress it inline + * Attempt to compress it inline * ---------- */ i = biggest_attno; old_value = toast_values[i]; + new_value = toast_compress_datum(old_value); - toast_values[i] = toast_compress_datum(toast_values[i]); - - if (toast_free[i]) - pfree(DatumGetPointer(old_value)); - - toast_free[i] = true; - toast_sizes[i] = VARATT_SIZE(toast_values[i]); - - need_change = true; - need_free = true; + if (DatumGetPointer(new_value) != NULL) + { + /* successful compression */ + if (toast_free[i]) + pfree(DatumGetPointer(old_value)); + toast_values[i] = new_value; + toast_free[i] = true; + toast_sizes[i] = VARATT_SIZE(toast_values[i]); + need_change = true; + need_free = true; + } + else + { + /* incompressible data, ignore on subsequent compression passes */ + toast_action[i] = 'x'; + } } /* ---------- @@ -690,6 +713,10 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup) * toast_compress_datum - * * Create a compressed version of a varlena datum + * + * If we fail (ie, compressed result is actually bigger than original) + * then return NULL. We must not use compressed data if it'd expand + * the tuple! * ---------- */ static Datum @@ -697,13 +724,22 @@ toast_compress_datum(Datum value) { varattrib *tmp; - tmp = (varattrib *)palloc(sizeof(PGLZ_Header) + VARATT_SIZE(value)); + tmp = (varattrib *) palloc(sizeof(PGLZ_Header) + VARATT_SIZE(value)); pglz_compress(VARATT_DATA(value), VARATT_SIZE(value) - VARHDRSZ, - (PGLZ_Header *)tmp, - PGLZ_strategy_default); - VARATT_SIZEP(tmp) |= VARATT_FLAG_COMPRESSED; - - return PointerGetDatum(tmp); + (PGLZ_Header *) tmp, + PGLZ_strategy_default); + if (VARATT_SIZE(tmp) < VARATT_SIZE(value)) + { + /* successful compression */ + VARATT_SIZEP(tmp) |= VARATT_FLAG_COMPRESSED; + return PointerGetDatum(tmp); + } + else + { + /* incompressible data */ + pfree(tmp); + return PointerGetDatum(NULL); + } } |