Re: Move pg_attribute.attcompression to earlier in struct for reduced size?

[Michael Paquier]

On Tue, May 18, 2021 at 10:24:36AM +0900, Michael Paquier wrote:
> If you switch attcompression, I'd say to go for the others while on
> it.  It would not be the first time in history there is a catalog
> version bump between betas.

This is still an open item.  FWIW, I can get behind the reordering
proposed by Tom for the consistency gained with pg_type, leading to
the attached to reduce the size of FormData_pg_attribute from 116b to
112b.
--
Michael

diff --git a/src/include/catalog/pg_attribute.h b/src/include/catalog/pg_attribute.h
index 560f8f00bb..b47e5fa2e7 100644
--- a/src/include/catalog/pg_attribute.h
+++ b/src/include/catalog/pg_attribute.h
@@ -111,6 +111,12 @@ CATALOG(pg_attribute,1249,AttributeRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(75,
 	 */
 	bool		attbyval;
 
+	/*
+	 * attalign is a copy of the typalign field from pg_type for this
+	 * attribute.  See atttypid comments above.
+	 */
+	char		attalign;
+
 	/*----------
 	 * attstorage tells for VARLENA attributes, what the heap access
 	 * methods can do to it if a given tuple doesn't fit into a page.
@@ -120,10 +126,10 @@ CATALOG(pg_attribute,1249,AttributeRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(75,
 	char		attstorage;
 
 	/*
-	 * attalign is a copy of the typalign field from pg_type for this
-	 * attribute.  See atttypid comments above.
+	 * compression method.  Must be InvalidCompressionMethod if and only if
+	 * typstorage is 'plain' or 'external'.
 	 */
-	char		attalign;
+	char		attcompression BKI_DEFAULT('\0');
 
 	/* This flag represents the "NOT NULL" constraint */
 	bool		attnotnull;
@@ -160,12 +166,6 @@ CATALOG(pg_attribute,1249,AttributeRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(75,
 	/* attribute's collation, if any */
 	Oid			attcollation BKI_LOOKUP_OPT(pg_collation);
 
-	/*
-	 * compression method.  Must be InvalidCompressionMethod if and only if
-	 * typstorage is 'plain' or 'external'.
-	 */
-	char		attcompression BKI_DEFAULT('\0');
-
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* NOTE: The following fields are not present in tuple descriptors. */
 
@@ -193,7 +193,7 @@ CATALOG(pg_attribute,1249,AttributeRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(75,
  * can access fields beyond attcollation except in a real tuple!
  */
 #define ATTRIBUTE_FIXED_PART_SIZE \
-	(offsetof(FormData_pg_attribute,attcompression) + sizeof(char))
+	(offsetof(FormData_pg_attribute,attcollation) + sizeof(Oid))
 
 /* ----------------
  *		Form_pg_attribute corresponds to a pointer to a tuple with

signature.asc
Description: PGP signature