From dbab0c07e5ba1f19a991da2d72972a8fe9a41bda Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Mon, 14 Jun 2021 09:25:50 +0900 Subject: [PATCH] Remove forced toast recompression in VACUUM FULL/CLUSTER MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The extra checks added by the recompression of toast data introduced in bbe0a81 is proving to have a performance impact on VACUUM or CLUSTER even if no recompression is done. This is more noticeable with more toastable columns that contain non-NULL values. Improvements could be done to make those extra checks less expensive, but that's not material for 14 at this stage, and we are not sure either if the code path of VACUUM FULL/CLUSTER is adapted for this job. Per discussion with several people, including Andres Freund, Robert Haas, Álvaro Herrera, Tom Lane and myself. Discussion: https://postgr.es/m/20210527003144.xxqppojoiwurc2iz@alap3.anarazel.de --- doc/src/sgml/ref/alter_table.sgml | 3 +- src/backend/access/heap/heapam_handler.c | 61 +-------------------- src/test/regress/expected/compression.out | 4 +- src/test/regress/expected/compression_1.out | 2 +- src/test/regress/sql/compression.sql | 2 +- 5 files changed, 6 insertions(+), 66 deletions(-) diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml index 939d3fe273..c5e5e84e06 100644 --- a/doc/src/sgml/ref/alter_table.sgml +++ b/doc/src/sgml/ref/alter_table.sgml @@ -394,8 +394,7 @@ WITH ( MODULUS numeric_literal, REM values inserted in future will be compressed (if the storage mode permits compression at all). This does not cause the table to be rewritten, so existing data may still - be compressed with other compression methods. If the table is rewritten with - VACUUM FULL or CLUSTER, or restored + be compressed with other compression methods. If the table is restored with pg_restore, then all values are rewritten with the configured compression method. However, when data is inserted from another relation (for example, diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c index e2cd79ec54..1b8b640012 100644 --- a/src/backend/access/heap/heapam_handler.c +++ b/src/backend/access/heap/heapam_handler.c @@ -19,7 +19,6 @@ */ #include "postgres.h" -#include "access/detoast.h" #include "access/genam.h" #include "access/heapam.h" #include "access/heaptoast.h" @@ -27,7 +26,6 @@ #include "access/rewriteheap.h" #include "access/syncscan.h" #include "access/tableam.h" -#include "access/toast_compression.h" #include "access/tsmapi.h" #include "access/xact.h" #include "catalog/catalog.h" @@ -2463,64 +2461,14 @@ reform_and_rewrite_tuple(HeapTuple tuple, TupleDesc newTupDesc = RelationGetDescr(NewHeap); HeapTuple copiedTuple; int i; - bool values_free[MaxTupleAttributeNumber]; - - memset(values_free, 0, newTupDesc->natts * sizeof(bool)); heap_deform_tuple(tuple, oldTupDesc, values, isnull); + /* Be sure to null out any dropped columns */ for (i = 0; i < newTupDesc->natts; i++) { - /* Be sure to null out any dropped columns */ if (TupleDescAttr(newTupDesc, i)->attisdropped) isnull[i] = true; - else if (!isnull[i] && TupleDescAttr(newTupDesc, i)->attlen == -1) - { - /* - * Use this opportunity to force recompression of any data that's - * compressed with some TOAST compression method other than the - * one configured for the column. We don't actually need to - * perform the compression here; we just need to decompress. That - * will trigger recompression later on. - */ - struct varlena *new_value; - ToastCompressionId cmid; - char cmethod; - char targetmethod; - - new_value = (struct varlena *) DatumGetPointer(values[i]); - cmid = toast_get_compression_id(new_value); - - /* nothing to be done for uncompressed data */ - if (cmid == TOAST_INVALID_COMPRESSION_ID) - continue; - - /* convert existing compression id to compression method */ - switch (cmid) - { - case TOAST_PGLZ_COMPRESSION_ID: - cmethod = TOAST_PGLZ_COMPRESSION; - break; - case TOAST_LZ4_COMPRESSION_ID: - cmethod = TOAST_LZ4_COMPRESSION; - break; - default: - elog(ERROR, "invalid compression method id %d", cmid); - cmethod = '\0'; /* keep compiler quiet */ - } - - /* figure out what the target method is */ - targetmethod = TupleDescAttr(newTupDesc, i)->attcompression; - if (!CompressionMethodIsValid(targetmethod)) - targetmethod = default_toast_compression; - - /* if compression method doesn't match then detoast the value */ - if (targetmethod != cmethod) - { - values[i] = PointerGetDatum(detoast_attr(new_value)); - values_free[i] = true; - } - } } copiedTuple = heap_form_tuple(newTupDesc, values, isnull); @@ -2528,13 +2476,6 @@ reform_and_rewrite_tuple(HeapTuple tuple, /* The heap rewrite module does the rest */ rewrite_heap_tuple(rwstate, tuple, copiedTuple); - /* Free any value detoasted previously */ - for (i = 0; i < newTupDesc->natts; i++) - { - if (values_free[i]) - pfree(DatumGetPointer(values[i])); - } - heap_freetuple(copiedTuple); } diff --git a/src/test/regress/expected/compression.out b/src/test/regress/expected/compression.out index 5c645e4650..4c997e2602 100644 --- a/src/test/regress/expected/compression.out +++ b/src/test/regress/expected/compression.out @@ -297,7 +297,7 @@ SELECT pg_column_compression(f1) FROM cmpart2; lz4 (2 rows) ---vacuum full to recompress the data +-- VACUUM FULL does not recompress SELECT pg_column_compression(f1) FROM cmdata; pg_column_compression ----------------------- @@ -309,7 +309,7 @@ VACUUM FULL cmdata; SELECT pg_column_compression(f1) FROM cmdata; pg_column_compression ----------------------- - lz4 + pglz lz4 (2 rows) diff --git a/src/test/regress/expected/compression_1.out b/src/test/regress/expected/compression_1.out index aac96037fc..15a23924ec 100644 --- a/src/test/regress/expected/compression_1.out +++ b/src/test/regress/expected/compression_1.out @@ -293,7 +293,7 @@ SELECT pg_column_compression(f1) FROM cmpart2; ----------------------- (0 rows) ---vacuum full to recompress the data +-- VACUUM FULL does not recompress SELECT pg_column_compression(f1) FROM cmdata; pg_column_compression ----------------------- diff --git a/src/test/regress/sql/compression.sql b/src/test/regress/sql/compression.sql index 35557c1f7d..86332dcc51 100644 --- a/src/test/regress/sql/compression.sql +++ b/src/test/regress/sql/compression.sql @@ -126,7 +126,7 @@ INSERT INTO cmpart VALUES (repeat('123456789', 4004)); SELECT pg_column_compression(f1) FROM cmpart1; SELECT pg_column_compression(f1) FROM cmpart2; ---vacuum full to recompress the data +-- VACUUM FULL does not recompress SELECT pg_column_compression(f1) FROM cmdata; VACUUM FULL cmdata; SELECT pg_column_compression(f1) FROM cmdata;