BRIN auto-summarization

Previously, only VACUUM would cause a page range to get initially
summarized by BRIN indexes, which for some use cases takes too much time
since the inserts occur.  To avoid the delay, have brininsert request a
summarization run for the previous range as soon as the first tuple is
inserted into the first page of the next range.  Autovacuum is in charge
of processing these requests, after doing all the regular vacuuming/
analyzing work on tables.

This doesn't impose any new tasks on autovacuum, because autovacuum was
already in charge of doing summarizations.  The only actual effect is to
change the timing, i.e. that it occurs earlier.  For this reason, we
don't go any great lengths to record these requests very robustly; if
they are lost because of a server crash or restart, they will happen at
a later time anyway.

Most of the new code here is in autovacuum, which can now be told about
"work items" to process.  This can be used for other things such as GIN
pending list cleaning, perhaps visibility map bit setting, both of which
are currently invoked during vacuum, but do not really depend on vacuum
taking place.

The requests are at the page range level, a granularity for which we did
not have SQL-level access; we only had index-level summarization
requests via brin_summarize_new_values().  It seems reasonable to add
SQL-level access to range-level summarization too, so add a function
brin_summarize_range() to do that.

Authors: Álvaro Herrera, based on sketch from Simon Riggs.
Reviewed-by: Thomas Munro.
Discussion: https://postgr.es/m/20170301045823.vneqdqkmsd4as4ds@alvherre.pgsql

2 files changed, 76 insertions, 0 deletions

diff --git a/src/test/regress/expected/brin.out b/src/test/regress/expected/brin.out
index f0008dd31b4..3e0a0381eda 100644
--- a/src/test/regress/expected/brin.out
+++ b/src/test/regress/expected/brin.out
@@ -406,3 +406,51 @@ SELECT brin_summarize_new_values('brinidx'); -- ok, no change expected
                          0
 (1 row)
 
+-- Test brin_summarize_range
+CREATE TABLE brin_summarize (
+    value int
+) WITH (fillfactor=10, autovacuum_enabled=false);
+CREATE INDEX brin_summarize_idx ON brin_summarize USING brin (value) WITH (pages_per_range=2);
+-- Fill a few pages
+DO $$
+DECLARE curtid tid;
+BEGIN
+  LOOP
+    INSERT INTO brin_summarize VALUES (1) RETURNING ctid INTO curtid;
+    EXIT WHEN curtid > tid '(2, 0)';
+  END LOOP;
+END;
+$$;
+-- summarize one range
+SELECT brin_summarize_range('brin_summarize_idx', 0);
+ brin_summarize_range 
+----------------------
+                    1
+(1 row)
+
+-- nothing: already summarized
+SELECT brin_summarize_range('brin_summarize_idx', 1);
+ brin_summarize_range 
+----------------------
+                    0
+(1 row)
+
+-- summarize one range
+SELECT brin_summarize_range('brin_summarize_idx', 2);
+ brin_summarize_range 
+----------------------
+                    1
+(1 row)
+
+-- nothing: page doesn't exist in table
+SELECT brin_summarize_range('brin_summarize_idx', 4294967295);
+ brin_summarize_range 
+----------------------
+                    0
+(1 row)
+
+-- invalid block number values
+SELECT brin_summarize_range('brin_summarize_idx', -1);
+ERROR:  block number out of range: -1
+SELECT brin_summarize_range('brin_summarize_idx', 4294967296);
+ERROR:  block number out of range: 4294967296
diff --git a/src/test/regress/sql/brin.sql b/src/test/regress/sql/brin.sql
index 5bf53873f77..da73df36593 100644
--- a/src/test/regress/sql/brin.sql
+++ b/src/test/regress/sql/brin.sql
@@ -409,3 +409,31 @@ UPDATE brintest SET textcol = '' WHERE textcol IS NOT NULL;
 SELECT brin_summarize_new_values('brintest'); -- error, not an index
 SELECT brin_summarize_new_values('tenk1_unique1'); -- error, not a BRIN index
 SELECT brin_summarize_new_values('brinidx'); -- ok, no change expected
+
+-- Test brin_summarize_range
+CREATE TABLE brin_summarize (
+    value int
+) WITH (fillfactor=10, autovacuum_enabled=false);
+CREATE INDEX brin_summarize_idx ON brin_summarize USING brin (value) WITH (pages_per_range=2);
+-- Fill a few pages
+DO $$
+DECLARE curtid tid;
+BEGIN
+  LOOP
+    INSERT INTO brin_summarize VALUES (1) RETURNING ctid INTO curtid;
+    EXIT WHEN curtid > tid '(2, 0)';
+  END LOOP;
+END;
+$$;
+
+-- summarize one range
+SELECT brin_summarize_range('brin_summarize_idx', 0);
+-- nothing: already summarized
+SELECT brin_summarize_range('brin_summarize_idx', 1);
+-- summarize one range
+SELECT brin_summarize_range('brin_summarize_idx', 2);
+-- nothing: page doesn't exist in table
+SELECT brin_summarize_range('brin_summarize_idx', 4294967295);
+-- invalid block number values
+SELECT brin_summarize_range('brin_summarize_idx', -1);
+SELECT brin_summarize_range('brin_summarize_idx', 4294967296);