Subject: [PATCH v24 5/7] fixups.patch

From: Robert Haas <[email-masked]>
Date: Wed, 10 Feb 2021 16:56:17 -0500

---
 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"