diff options
Diffstat (limited to 'src/backend/access/heap/tuptoaster.c')
| -rw-r--r-- | src/backend/access/heap/tuptoaster.c | 92 |
1 files changed, 66 insertions, 26 deletions
diff --git a/src/backend/access/heap/tuptoaster.c b/src/backend/access/heap/tuptoaster.c index 3ace2042493..40f5d72056e 100644 --- a/src/backend/access/heap/tuptoaster.c +++ b/src/backend/access/heap/tuptoaster.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.83 2008/02/29 17:47:41 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.84 2008/03/07 23:20:21 tgl Exp $ * * * INTERFACE ROUTINES @@ -576,7 +576,8 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup, /* ---------- * Compress and/or save external until data fits into target length * - * 1: Inline compress attributes with attstorage 'x' + * 1: Inline compress attributes with attstorage 'x', and store very + * large attributes with attstorage 'x' or 'e' external immediately * 2: Store attributes with attstorage 'x' or 'e' external * 3: Inline compress attributes with attstorage 'm' * 4: Store attributes with attstorage 'm' external @@ -595,7 +596,8 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup, maxDataLen = TOAST_TUPLE_TARGET - hoff; /* - * Look for attributes with attstorage 'x' to compress + * Look for attributes with attstorage 'x' to compress. Also find large + * attributes with attstorage 'x' or 'e', and store them external. */ while (heap_compute_data_size(tupleDesc, toast_values, toast_isnull) > maxDataLen) @@ -606,7 +608,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup, Datum new_value; /* - * Search for the biggest yet uncompressed internal attribute + * Search for the biggest yet unprocessed internal attribute */ for (i = 0; i < numAttrs; i++) { @@ -616,7 +618,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup, continue; /* can't happen, toast_action would be 'p' */ if (VARATT_IS_COMPRESSED(toast_values[i])) continue; - if (att[i]->attstorage != 'x') + if (att[i]->attstorage != 'x' && att[i]->attstorage != 'e') continue; if (toast_sizes[i] > biggest_size) { @@ -629,30 +631,58 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup, break; /* - * Attempt to compress it inline + * Attempt to compress it inline, if it has attstorage 'x' */ i = biggest_attno; - old_value = toast_values[i]; - new_value = toast_compress_datum(old_value); + if (att[i]->attstorage == 'x') + { + old_value = toast_values[i]; + new_value = toast_compress_datum(old_value); - if (DatumGetPointer(new_value) != NULL) + 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] = VARSIZE(toast_values[i]); + need_change = true; + need_free = true; + } + else + { + /* incompressible, ignore on subsequent compression passes */ + toast_action[i] = 'x'; + } + } + else { - /* successful compression */ + /* has attstorage 'e', ignore on subsequent compression passes */ + toast_action[i] = 'x'; + } + + /* + * If this value is by itself more than maxDataLen (after compression + * if any), push it out to the toast table immediately, if possible. + * This avoids uselessly compressing other fields in the common case + * where we have one long field and several short ones. + * + * XXX maybe the threshold should be less than maxDataLen? + */ + if (toast_sizes[i] > maxDataLen && + rel->rd_rel->reltoastrelid != InvalidOid) + { + old_value = toast_values[i]; + toast_action[i] = 'p'; + toast_values[i] = toast_save_datum(rel, toast_values[i], + use_wal, use_fsm); if (toast_free[i]) pfree(DatumGetPointer(old_value)); - toast_values[i] = new_value; toast_free[i] = true; - toast_sizes[i] = VARSIZE(toast_values[i]); need_change = true; need_free = true; } - else - { - /* - * incompressible data, ignore on subsequent compression passes - */ - toast_action[i] = 'x'; - } } /* @@ -761,9 +791,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup, } else { - /* - * incompressible data, ignore on subsequent compression passes - */ + /* incompressible, ignore on subsequent compression passes */ toast_action[i] = 'x'; } } @@ -1047,16 +1075,28 @@ toast_compress_datum(Datum value) Assert(!VARATT_IS_COMPRESSED(value)); /* - * No point in wasting a palloc cycle if value is too short for - * compression + * No point in wasting a palloc cycle if value size is out of the + * allowed range for compression */ - if (valsize < PGLZ_strategy_default->min_input_size) + if (valsize < PGLZ_strategy_default->min_input_size || + valsize > PGLZ_strategy_default->max_input_size) return PointerGetDatum(NULL); tmp = (struct varlena *) palloc(PGLZ_MAX_OUTPUT(valsize)); + + /* + * We recheck the actual size even if pglz_compress() reports success, + * because it might be satisfied with having saved as little as one byte + * in the compressed data --- which could turn into a net loss once you + * consider header and alignment padding. Worst case, the compressed + * format might require three padding bytes (plus header, which is included + * in VARSIZE(tmp)), whereas the uncompressed format would take only one + * header byte and no padding if the value is short enough. So we insist + * on a savings of more than 2 bytes to ensure we have a gain. + */ if (pglz_compress(VARDATA_ANY(value), valsize, (PGLZ_Header *) tmp, PGLZ_strategy_default) && - VARSIZE(tmp) < VARSIZE_ANY(value)) + VARSIZE(tmp) < valsize - 2) { /* successful compression */ return PointerGetDatum(tmp); |