Support varlena fields with single-byte headers and unaligned storage.

This commit breaks any code that assumes that the mere act of forming a tuple
(without writing it to disk) does not "toast" any fields.  While all available
regression tests pass, I'm not totally sure that we've fixed every nook and
cranny, especially in contrib.

Greg Stark with some help from Tom Lane

4 files changed, 54 insertions, 0 deletions

diff --git a/src/test/regress/expected/rowtypes.out b/src/test/regress/expected/rowtypes.out
index dbf163cd695..6af1aa705fd 100644
--- a/src/test/regress/expected/rowtypes.out
+++ b/src/test/regress/expected/rowtypes.out
@@ -248,3 +248,20 @@ order by thousand, tenthous;
       999 |     9999
 (25 rows)
 
+-- Check some corner cases involving empty rowtypes
+select ROW();
+ row 
+-----
+ ()
+(1 row)
+
+select ROW() IS NULL;
+ ?column? 
+----------
+ t
+(1 row)
+
+select ROW() = ROW();
+ERROR:  cannot compare rows of zero length
+LINE 1: select ROW() = ROW();
+                     ^
diff --git a/src/test/regress/expected/strings.out b/src/test/regress/expected/strings.out
index e11dfc35d78..bd82846b1a4 100644
--- a/src/test/regress/expected/strings.out
+++ b/src/test/regress/expected/strings.out
@@ -941,6 +941,26 @@ SELECT substr(f1, 99995, 10) from toasttest;
 (4 rows)
 
 DROP TABLE toasttest;
+-- test internally compressing datums
+-- this tests compressing a datum to a very small size which exercises a
+-- corner case in packed-varlena handling: even though small, the compressed
+-- datum must be given a 4-byte header because there are no bits to indicate
+-- compression in a 1-byte header
+CREATE TABLE toasttest (c char(4096));
+INSERT INTO toasttest VALUES('x');
+SELECT length(c), c::text FROM toasttest;
+ length | c 
+--------+---
+      1 | x
+(1 row)
+
+SELECT c FROM toasttest;
+                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                c                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ x                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
+(1 row)
+
+DROP TABLE toasttest;
 --
 -- test length
 --
diff --git a/src/test/regress/sql/rowtypes.sql b/src/test/regress/sql/rowtypes.sql
index 779b20e8631..7e5c554d3b7 100644
--- a/src/test/regress/sql/rowtypes.sql
+++ b/src/test/regress/sql/rowtypes.sql
@@ -109,3 +109,7 @@ select thousand, tenthous from tenk1
 where (thousand, tenthous) >= (997, 5000)
 order by thousand, tenthous;
 
+-- Check some corner cases involving empty rowtypes
+select ROW();
+select ROW() IS NULL;
+select ROW() = ROW();
diff --git a/src/test/regress/sql/strings.sql b/src/test/regress/sql/strings.sql
index 389ff63517f..800028e4fcb 100644
--- a/src/test/regress/sql/strings.sql
+++ b/src/test/regress/sql/strings.sql
@@ -329,6 +329,19 @@ SELECT substr(f1, 99995, 10) from toasttest;
 
 DROP TABLE toasttest;
 
+-- test internally compressing datums
+
+-- this tests compressing a datum to a very small size which exercises a
+-- corner case in packed-varlena handling: even though small, the compressed
+-- datum must be given a 4-byte header because there are no bits to indicate
+-- compression in a 1-byte header
+
+CREATE TABLE toasttest (c char(4096));
+INSERT INTO toasttest VALUES('x');
+SELECT length(c), c::text FROM toasttest;
+SELECT c FROM toasttest;
+DROP TABLE toasttest;
+
 --
 -- test length
 --