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* [PATCH v24 5/7] fixups.patch
@ 2021-02-10 21:56 Robert Haas <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Robert Haas @ 2021-02-10 21:56 UTC (permalink / raw)
---
doc/src/sgml/ddl.sgml | 3 ---
doc/src/sgml/ref/create_table.sgml | 15 +++++++++++----
src/backend/access/common/detoast.c | 5 ++---
src/backend/access/compression/compress_lz4.c | 10 +++++-----
src/backend/executor/nodeModifyTable.c | 2 +-
src/include/nodes/execnodes.h | 4 ++--
6 files changed, 21 insertions(+), 18 deletions(-)
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 4d7ed698b9..1e9a4625cc 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -3762,9 +3762,6 @@ CREATE TABLE measurement (
<productname>PostgreSQL</productname>
tables (or, possibly, foreign tables). It is possible to specify a
tablespace and storage parameters for each partition separately.
- By default, each column in a partition inherits the compression method
- from parent table's column, however a different compression method can be
- set for each partition.
</para>
<para>
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index 51a7a977a5..a4b297340f 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -997,10 +997,17 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
<term><literal>COMPRESSION <replaceable class="parameter">compression_method</replaceable></literal></term>
<listitem>
<para>
- This sets the compression method for a column. The supported compression
- methods are <literal>pglz</literal> and <literal>lz4</literal>.
- <literal>lz4</literal> is available only if <literal>--with-lz4</literal>
- was used when building <productname>PostgreSQL</productname>. The default
+ The <literal>COMPRESSION</literal> clause sets the compression method
+ for a column. Compression is supported only for variable-width data
+ types, and is used only for columns whose storage type is main or
+ extended. (See <xref linkend="sql-altertable"/> for information on
+ column storage types.) Setting this property for a partitioned table
+ has no direct effect, because such tables have no storage of their own,
+ but the configured value is inherited by newly-created partitions.
+ The supported compression methods are <literal>pglz</literal> and
+ <literal>lz4</literal>. <literal>lz4</literal> is available only if
+ <literal>--with-lz4</literal> was used when building
+ <productname>PostgreSQL</productname>. The default
is <literal>pglz</literal>.
</para>
</listitem>
diff --git a/src/backend/access/common/detoast.c b/src/backend/access/common/detoast.c
index b78d49167b..95d5b1c12a 100644
--- a/src/backend/access/common/detoast.c
+++ b/src/backend/access/common/detoast.c
@@ -477,8 +477,8 @@ toast_get_compression_oid(struct varlena *attr)
return InvalidOid;
/*
- * Just fetch the toast compress header to know the compression method
- * in the compressed data.
+ * Fetch just enough of the value to examine the compression header,
+ * so that we can find out the compression method.
*/
attr = toast_fetch_datum_slice(attr, 0, VARHDRSZ_COMPRESS);
}
@@ -503,7 +503,6 @@ toast_get_compression_handler(struct varlena *attr)
cmid = TOAST_COMPRESS_METHOD(attr);
- /* Get the handler routines for the compression method */
switch (cmid)
{
case PGLZ_COMPRESSION_ID:
diff --git a/src/backend/access/compression/compress_lz4.c b/src/backend/access/compression/compress_lz4.c
index 1856cf7df7..3079eff7eb 100644
--- a/src/backend/access/compression/compress_lz4.c
+++ b/src/backend/access/compression/compress_lz4.c
@@ -23,7 +23,7 @@
/*
* lz4_cmcompress - compression routine for lz4 compression method
*
- * Compresses source into dest using the default strategy. Returns the
+ * Compresses source into dest using the LZ4 defaults. Returns the
* compressed varlena, or NULL if compression fails.
*/
static struct varlena *
@@ -42,8 +42,8 @@ lz4_cmcompress(const struct varlena *value)
valsize = VARSIZE_ANY_EXHDR(value);
/*
- * Get maximum size of the compressed data that lz4 compression may output
- * and allocate the memory for holding the compressed data and the header.
+ * Figure out the maximum possible size of the LZ4 output, add the bytes
+ * that will be needed for varlena overhead, and allocate that amount.
*/
max_size = LZ4_compressBound(valsize);
tmp = (struct varlena *) palloc(max_size + VARHDRSZ_COMPRESS);
@@ -83,10 +83,10 @@ lz4_cmdecompress(const struct varlena *value)
int32 rawsize;
struct varlena *result;
- /* allocate memory for holding the uncompressed data */
+ /* allocate memory for the uncompressed data */
result = (struct varlena *) palloc(VARRAWSIZE_4B_C(value) + VARHDRSZ);
- /* decompress data using lz4 routine */
+ /* decompress the data */
rawsize = LZ4_decompress_safe((char *) value + VARHDRSZ_COMPRESS,
VARDATA(result),
VARSIZE(value) - VARHDRSZ_COMPRESS,
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index f77deee399..920d9dd0d5 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -2117,7 +2117,7 @@ CompareCompressionMethodAndDecompress(TupleTableSlot *slot,
TupleTableSlot *newslot = *outslot;
/*
- * If the called has passed an invalid slot then create a new slot.
+ * If the caller has passed an invalid slot then create a new slot.
* Otherwise, just clear the existing tuple from the slot. This slot
* should be stored by the caller so that it can be reused for
* decompressing the subsequent tuples.
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 18e8ecfd90..d8483c36b3 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1183,8 +1183,8 @@ typedef struct ModifyTableState
TupleTableSlot *mt_root_tuple_slot;
/*
- * Slot for storing the modified tuple, incase the target attribute's
- * compression method doesn't match with the source table.
+ * Slot for storing the modified tuple, in case the target attribute's
+ * compression method doesn't match that of the source table.
*/
TupleTableSlot *mt_decompress_tuple_slot;
--
2.17.0
--YZ5djTAD1cGYuMQK
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v24-0006-alter-table-set-compression.patch"
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: partitioning and identity column
@ 2023-11-13 10:21 Peter Eisentraut <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Peter Eisentraut @ 2023-11-13 10:21 UTC (permalink / raw)
To: Ashutosh Bapat <[email protected]>; PostgreSQL Hackers <[email protected]>
On 27.10.23 13:32, Ashutosh Bapat wrote:
> I think we should fix these anomalies as follows
> 1. Allow identity columns to be added to the partitioned table
> irrespective of whether they have partitions of not.
> 2. Propagate identity property to partitions.
> 3. Use the same underlying sequence for getting default value of an
> identity column when INSERTing directly in a partition.
> 4. Disallow attaching a partition with identity column.
>
> 1 will fix inconsistencies in Behaviour 3 and 4. 2 and 3 will fix
> anomalies in Behaviour 1. 4 will fix Behaviour 2.
This makes sense to me.
Note, here is a writeup about the behavior of generated columns with
partitioning:
https://www.postgresql.org/docs/devel/ddl-generated-columns.html. It
would be useful if we documented the behavior of identity columns
similarly. (I'm not saying the behavior has to match.)
One thing that's not clear to me is what should happen if you have a
partitioned table with an identity column and you try to attach a
partition that has its own identity definition for that column. I
suppose we shouldn't allow that. (The equivalent case for generated
columns is allowed.)
^ permalink raw reply [nested|flat] 2+ messages in thread
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2021-02-10 21:56 [PATCH v24 5/7] fixups.patch Robert Haas <[email protected]>
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