v1-0001-pg_plan_advice-Add-NO_SCAN-and-NO_JOIN_METHOD-tag.patch
text/plain
Filename: v1-0001-pg_plan_advice-Add-NO_SCAN-and-NO_JOIN_METHOD-tag.patch
Type: text/plain
Part: 0
Patch
Format: format-patch
Series: patch v1-0001
Subject: pg_plan_advice: Add NO_SCAN and NO_JOIN_METHOD tags
| File | + | − |
|---|---|---|
| contrib/pg_plan_advice/expected/no_join.out | 288 | 0 |
| contrib/pg_plan_advice/expected/no_scan.out | 197 | 0 |
| contrib/pg_plan_advice/Makefile | 2 | 2 |
| contrib/pg_plan_advice/pgpa_ast.c | 52 | 0 |
| contrib/pg_plan_advice/pgpa_ast.h | 13 | 0 |
| contrib/pg_plan_advice/pgpa_parser.y | 10 | 0 |
| contrib/pg_plan_advice/pgpa_planner.c | 164 | 20 |
| contrib/pg_plan_advice/pgpa_scanner.l | 6 | 1 |
| contrib/pg_plan_advice/pgpa_trove.c | 13 | 0 |
| contrib/pg_plan_advice/pgpa_walker.c | 71 | 0 |
| contrib/pg_plan_advice/sql/no_join.sql | 92 | 0 |
| contrib/pg_plan_advice/sql/no_scan.sql | 88 | 0 |
| doc/src/sgml/pgplanadvice.sgml | 129 | 0 |
From 76628bd8aee1b8977e416f45162aca3795e75ba9 Mon Sep 17 00:00:00 2001
From: Florin Irion <florin.irion@enterprisedb.com>
Date: Thu, 18 Jun 2026 14:28:50 +0200
Subject: [PATCH v1] pg_plan_advice: Add NO_SCAN and NO_JOIN_METHOD tags
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Add NO_SEQ_SCAN, NO_INDEX_SCAN, NO_INDEX_ONLY_SCAN,
NO_BITMAP_HEAP_SCAN, and NO_TID_SCAN as negative scan-method
directives; and NO_HASH_JOIN, NO_NESTED_LOOP (plus _PLAIN,
_MEMOIZE, _MATERIALIZE variants), and NO_MERGE_JOIN (plus _PLAIN,
_MATERIALIZE variants) as negative join-method directives.
Each NO_ tag is the logical complement of its positive counterpart.
Scan NO_ tags use simple_target_list (sublists invalid); join NO_
tags use generic_target_list (sublists allowed). Because of this,
both the scanner and the parser only need to handle the NO_ scan
tags explicitly: the scanner classifies them as TOK_TAG_SIMPLE and
the parser resolves their names in the TOK_TAG_SIMPLE action. The
NO_ join tags fall through to the default TOK_TAG_GENERIC branch,
where the tag is resolved generically by pgpa_parse_advice_tag, so
they need no scanner or parser change.
Conflict detection marks both a positive and its NO_ counterpart as
conflicting when they target the same relation and method.
NO_ join tags carry the same join-order constraint as their positive
counterparts: NO_HASH_JOIN(x) means x may not appear on the outer
(driving) side — equivalently, it means "use hash join or merge join
with x as inner". The constraint is semantically intrinsic, not
incidental.
---
contrib/pg_plan_advice/Makefile | 4 +-
contrib/pg_plan_advice/expected/no_join.out | 288 ++++++++++++++++++++
contrib/pg_plan_advice/expected/no_scan.out | 197 +++++++++++++
contrib/pg_plan_advice/pgpa_ast.c | 52 ++++
contrib/pg_plan_advice/pgpa_ast.h | 13 +
contrib/pg_plan_advice/pgpa_parser.y | 10 +
contrib/pg_plan_advice/pgpa_planner.c | 184 +++++++++++--
contrib/pg_plan_advice/pgpa_scanner.l | 7 +-
contrib/pg_plan_advice/pgpa_trove.c | 13 +
contrib/pg_plan_advice/pgpa_walker.c | 71 +++++
contrib/pg_plan_advice/sql/no_join.sql | 92 +++++++
contrib/pg_plan_advice/sql/no_scan.sql | 88 ++++++
doc/src/sgml/pgplanadvice.sgml | 129 +++++++++
13 files changed, 1125 insertions(+), 23 deletions(-)
create mode 100644 contrib/pg_plan_advice/expected/no_join.out
create mode 100644 contrib/pg_plan_advice/expected/no_scan.out
create mode 100644 contrib/pg_plan_advice/sql/no_join.sql
create mode 100644 contrib/pg_plan_advice/sql/no_scan.sql
diff --git a/contrib/pg_plan_advice/Makefile b/contrib/pg_plan_advice/Makefile
index d016723794d..2dfe36fef4c 100644
--- a/contrib/pg_plan_advice/Makefile
+++ b/contrib/pg_plan_advice/Makefile
@@ -19,8 +19,8 @@ HEADERS_pg_plan_advice = pg_plan_advice.h
PGFILEDESC = "pg_plan_advice - help the planner get the right plan"
-REGRESS = alternatives gather join_order join_strategy partitionwise \
- prepared scan semijoin syntax
+REGRESS = alternatives gather join_order join_strategy no_join no_scan \
+ partitionwise prepared scan semijoin syntax
EXTRA_INSTALL = contrib/tsm_system_time
diff --git a/contrib/pg_plan_advice/expected/no_join.out b/contrib/pg_plan_advice/expected/no_join.out
new file mode 100644
index 00000000000..5c3f3fdb772
--- /dev/null
+++ b/contrib/pg_plan_advice/expected/no_join.out
@@ -0,0 +1,288 @@
+LOAD 'pg_plan_advice';
+SET max_parallel_workers_per_gather = 0;
+CREATE TABLE no_join_dim (id serial primary key, dim text)
+ WITH (autovacuum_enabled = false);
+INSERT INTO no_join_dim (dim) SELECT random()::text FROM generate_series(1,100) g;
+VACUUM ANALYZE no_join_dim;
+CREATE TABLE no_join_fact (
+ id int primary key,
+ dim_id integer not null references no_join_dim (id)
+) WITH (autovacuum_enabled = false);
+INSERT INTO no_join_fact
+ SELECT g, (g%3)+1 FROM generate_series(1,100000) g;
+CREATE INDEX no_join_fact_dim_id ON no_join_fact (dim_id);
+VACUUM ANALYZE no_join_fact;
+-- Baseline: hash join with d on the inner side.
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+---------------------------------------
+ Hash Join
+ Hash Cond: (f.dim_id = d.id)
+ -> Seq Scan on no_join_fact f
+ -> Hash
+ -> Seq Scan on no_join_dim d
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ HASH_JOIN(d)
+ SEQ_SCAN(f d)
+ NO_GATHER(f d)
+(10 rows)
+
+-- NO_HASH_JOIN(d): d stays inner, planner falls back to another method.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+----------------------------------------------------------------
+ Nested Loop
+ -> Seq Scan on no_join_fact f
+ -> Memoize
+ Cache Key: f.dim_id
+ Cache Mode: logical
+ -> Index Scan using no_join_dim_pkey on no_join_dim d
+ Index Cond: (id = f.dim_id)
+ Supplied Plan Advice:
+ NO_HASH_JOIN(d) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ NESTED_LOOP_MEMOIZE(d)
+ SEQ_SCAN(f)
+ INDEX_SCAN(d public.no_join_dim_pkey)
+ NO_GATHER(f d)
+(15 rows)
+
+COMMIT;
+-- NO_HASH_JOIN(f): the join-order constraint forces f to the inner side.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Merge Join
+ Merge Cond: (d.id = f.dim_id)
+ -> Index Scan using no_join_dim_pkey on no_join_dim d
+ -> Index Scan using no_join_fact_dim_id on no_join_fact f
+ Supplied Plan Advice:
+ NO_HASH_JOIN(f) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(d f)
+ MERGE_JOIN_PLAIN(f)
+ INDEX_SCAN(d public.no_join_dim_pkey f public.no_join_fact_dim_id)
+ NO_GATHER(f d)
+(11 rows)
+
+COMMIT;
+-- NO_NESTED_LOOP(f): f forced inner, all NL variants forbidden -> merge join.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Merge Join
+ Merge Cond: (d.id = f.dim_id)
+ -> Index Scan using no_join_dim_pkey on no_join_dim d
+ -> Index Scan using no_join_fact_dim_id on no_join_fact f
+ Supplied Plan Advice:
+ NO_NESTED_LOOP(f) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(d f)
+ MERGE_JOIN_PLAIN(f)
+ INDEX_SCAN(d public.no_join_dim_pkey f public.no_join_fact_dim_id)
+ NO_GATHER(f d)
+(11 rows)
+
+COMMIT;
+-- NO_MERGE_JOIN(d): d already inner, hash join still allowed -> plan unchanged.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_MERGE_JOIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+---------------------------------------
+ Hash Join
+ Hash Cond: (f.dim_id = d.id)
+ -> Seq Scan on no_join_fact f
+ -> Hash
+ -> Seq Scan on no_join_dim d
+ Supplied Plan Advice:
+ NO_MERGE_JOIN(d) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ HASH_JOIN(d)
+ SEQ_SCAN(f d)
+ NO_GATHER(f d)
+(12 rows)
+
+COMMIT;
+-- Stacking: NO_HASH_JOIN(f) + NO_NESTED_LOOP(f) leaves only merge join.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(f) NO_NESTED_LOOP(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Merge Join
+ Merge Cond: (d.id = f.dim_id)
+ -> Index Scan using no_join_dim_pkey on no_join_dim d
+ -> Index Scan using no_join_fact_dim_id on no_join_fact f
+ Supplied Plan Advice:
+ NO_HASH_JOIN(f) /* matched */
+ NO_NESTED_LOOP(f) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(d f)
+ MERGE_JOIN_PLAIN(f)
+ INDEX_SCAN(d public.no_join_dim_pkey f public.no_join_fact_dim_id)
+ NO_GATHER(f d)
+(12 rows)
+
+COMMIT;
+-- Specific NO_ variants targeting d, already the inner side: forbidding any one
+-- NL or merge variant leaves hash join available, so the plan is unchanged.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP_PLAIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+-----------------------------------------
+ Hash Join
+ Hash Cond: (f.dim_id = d.id)
+ -> Seq Scan on no_join_fact f
+ -> Hash
+ -> Seq Scan on no_join_dim d
+ Supplied Plan Advice:
+ NO_NESTED_LOOP_PLAIN(d) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ HASH_JOIN(d)
+ SEQ_SCAN(f d)
+ NO_GATHER(f d)
+(12 rows)
+
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP_MEMOIZE(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+-------------------------------------------
+ Hash Join
+ Hash Cond: (f.dim_id = d.id)
+ -> Seq Scan on no_join_fact f
+ -> Hash
+ -> Seq Scan on no_join_dim d
+ Supplied Plan Advice:
+ NO_NESTED_LOOP_MEMOIZE(d) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ HASH_JOIN(d)
+ SEQ_SCAN(f d)
+ NO_GATHER(f d)
+(12 rows)
+
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP_MATERIALIZE(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+-----------------------------------------------
+ Hash Join
+ Hash Cond: (f.dim_id = d.id)
+ -> Seq Scan on no_join_fact f
+ -> Hash
+ -> Seq Scan on no_join_dim d
+ Supplied Plan Advice:
+ NO_NESTED_LOOP_MATERIALIZE(d) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ HASH_JOIN(d)
+ SEQ_SCAN(f d)
+ NO_GATHER(f d)
+(12 rows)
+
+SET LOCAL pg_plan_advice.advice = 'NO_MERGE_JOIN_PLAIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+----------------------------------------
+ Hash Join
+ Hash Cond: (f.dim_id = d.id)
+ -> Seq Scan on no_join_fact f
+ -> Hash
+ -> Seq Scan on no_join_dim d
+ Supplied Plan Advice:
+ NO_MERGE_JOIN_PLAIN(d) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ HASH_JOIN(d)
+ SEQ_SCAN(f d)
+ NO_GATHER(f d)
+(12 rows)
+
+SET LOCAL pg_plan_advice.advice = 'NO_MERGE_JOIN_MATERIALIZE(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+----------------------------------------------
+ Hash Join
+ Hash Cond: (f.dim_id = d.id)
+ -> Seq Scan on no_join_fact f
+ -> Hash
+ -> Seq Scan on no_join_dim d
+ Supplied Plan Advice:
+ NO_MERGE_JOIN_MATERIALIZE(d) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(f d)
+ HASH_JOIN(d)
+ SEQ_SCAN(f d)
+ NO_GATHER(f d)
+(12 rows)
+
+COMMIT;
+-- Conflict: same method required and forbidden; both marked conflicting.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'HASH_JOIN(f) NO_HASH_JOIN(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Merge Join
+ Merge Cond: (d.id = f.dim_id)
+ -> Index Scan using no_join_dim_pkey on no_join_dim d
+ -> Index Scan using no_join_fact_dim_id on no_join_fact f
+ Supplied Plan Advice:
+ HASH_JOIN(f) /* matched, conflicting, failed */
+ NO_HASH_JOIN(f) /* matched, conflicting */
+ Generated Plan Advice:
+ JOIN_ORDER(d f)
+ MERGE_JOIN_PLAIN(f)
+ INDEX_SCAN(d public.no_join_dim_pkey f public.no_join_fact_dim_id)
+ NO_GATHER(f d)
+(12 rows)
+
+COMMIT;
+-- No conflict: NO_HASH_JOIN(f) and a positive tag for a different method.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(f) NESTED_LOOP_PLAIN(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+ QUERY PLAN
+--------------------------------------------------------------
+ Nested Loop
+ -> Seq Scan on no_join_dim d
+ -> Index Scan using no_join_fact_dim_id on no_join_fact f
+ Index Cond: (dim_id = d.id)
+ Supplied Plan Advice:
+ NO_HASH_JOIN(f) /* matched */
+ NESTED_LOOP_PLAIN(f) /* matched */
+ Generated Plan Advice:
+ JOIN_ORDER(d f)
+ NESTED_LOOP_PLAIN(f)
+ SEQ_SCAN(d)
+ INDEX_SCAN(f public.no_join_fact_dim_id)
+ NO_GATHER(f d)
+(13 rows)
+
+COMMIT;
+DROP TABLE no_join_fact;
+DROP TABLE no_join_dim;
diff --git a/contrib/pg_plan_advice/expected/no_scan.out b/contrib/pg_plan_advice/expected/no_scan.out
new file mode 100644
index 00000000000..08f2a21b650
--- /dev/null
+++ b/contrib/pg_plan_advice/expected/no_scan.out
@@ -0,0 +1,197 @@
+LOAD 'pg_plan_advice';
+SET max_parallel_workers_per_gather = 0;
+SET seq_page_cost = 0.1;
+SET random_page_cost = 0.1;
+SET cpu_tuple_cost = 0;
+SET cpu_index_tuple_cost = 0;
+CREATE TABLE no_scan_table (a int primary key, b text)
+ WITH (autovacuum_enabled = false);
+INSERT INTO no_scan_table
+ SELECT g, 'some text ' || g FROM generate_series(1, 100000) g;
+VACUUM ANALYZE no_scan_table;
+-- Baselines without advice: seq scan for a full read, index scan for a lookup.
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table;
+ QUERY PLAN
+----------------------------
+ Seq Scan on no_scan_table
+ Generated Plan Advice:
+ SEQ_SCAN(no_scan_table)
+ NO_GATHER(no_scan_table)
+(4 rows)
+
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+ QUERY PLAN
+-------------------------------------------------------
+ Index Scan using no_scan_table_pkey on no_scan_table
+ Index Cond: (a = 1)
+ Generated Plan Advice:
+ INDEX_SCAN(no_scan_table public.no_scan_table_pkey)
+ NO_GATHER(no_scan_table)
+(5 rows)
+
+-- NO_SEQ_SCAN with no indexable qual: no alternative, so the advice fails.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table;
+ QUERY PLAN
+----------------------------------------------------
+ Seq Scan on no_scan_table
+ Disabled: true
+ Supplied Plan Advice:
+ NO_SEQ_SCAN(no_scan_table) /* matched, failed */
+ Generated Plan Advice:
+ SEQ_SCAN(no_scan_table)
+ NO_GATHER(no_scan_table)
+(7 rows)
+
+COMMIT;
+-- NO_SEQ_SCAN with an indexable qual: falls back to index scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+ QUERY PLAN
+-------------------------------------------------------
+ Index Scan using no_scan_table_pkey on no_scan_table
+ Index Cond: (a = 1)
+ Supplied Plan Advice:
+ NO_SEQ_SCAN(no_scan_table) /* matched */
+ Generated Plan Advice:
+ INDEX_SCAN(no_scan_table public.no_scan_table_pkey)
+ NO_GATHER(no_scan_table)
+(7 rows)
+
+COMMIT;
+-- NO_INDEX_SCAN: falls back to bitmap heap scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_INDEX_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+ QUERY PLAN
+-----------------------------------------------
+ Bitmap Heap Scan on no_scan_table
+ Recheck Cond: (a = 1)
+ -> Bitmap Index Scan on no_scan_table_pkey
+ Index Cond: (a = 1)
+ Supplied Plan Advice:
+ NO_INDEX_SCAN(no_scan_table) /* matched */
+ Generated Plan Advice:
+ BITMAP_HEAP_SCAN(no_scan_table)
+ NO_GATHER(no_scan_table)
+(9 rows)
+
+COMMIT;
+-- NO_INDEX_ONLY_SCAN: falls back to a plain index scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_INDEX_ONLY_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT a FROM no_scan_table WHERE a = 1;
+ QUERY PLAN
+-------------------------------------------------------
+ Index Scan using no_scan_table_pkey on no_scan_table
+ Index Cond: (a = 1)
+ Supplied Plan Advice:
+ NO_INDEX_ONLY_SCAN(no_scan_table) /* matched */
+ Generated Plan Advice:
+ INDEX_SCAN(no_scan_table public.no_scan_table_pkey)
+ NO_GATHER(no_scan_table)
+(7 rows)
+
+COMMIT;
+-- NO_BITMAP_HEAP_SCAN: with only a BRIN index available, falls back to seq scan.
+CREATE INDEX no_scan_table_b ON no_scan_table USING brin (b);
+VACUUM ANALYZE no_scan_table;
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_BITMAP_HEAP_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE b > 'some text 8';
+ QUERY PLAN
+----------------------------------------------------
+ Seq Scan on no_scan_table
+ Filter: (b > 'some text 8'::text)
+ Supplied Plan Advice:
+ NO_BITMAP_HEAP_SCAN(no_scan_table) /* matched */
+ Generated Plan Advice:
+ SEQ_SCAN(no_scan_table)
+ NO_GATHER(no_scan_table)
+(7 rows)
+
+COMMIT;
+-- NO_TID_SCAN: falls back to seq scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_TID_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE ctid = '(0,1)';
+ QUERY PLAN
+--------------------------------------------
+ Seq Scan on no_scan_table
+ Filter: (ctid = '(0,1)'::tid)
+ Supplied Plan Advice:
+ NO_TID_SCAN(no_scan_table) /* matched */
+ Generated Plan Advice:
+ SEQ_SCAN(no_scan_table)
+ NO_GATHER(no_scan_table)
+(7 rows)
+
+COMMIT;
+-- Multiple NO_ scan tags stack without conflict.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table) NO_BITMAP_HEAP_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+ QUERY PLAN
+-------------------------------------------------------
+ Index Scan using no_scan_table_pkey on no_scan_table
+ Index Cond: (a = 1)
+ Supplied Plan Advice:
+ NO_SEQ_SCAN(no_scan_table) /* matched */
+ NO_BITMAP_HEAP_SCAN(no_scan_table) /* matched */
+ Generated Plan Advice:
+ INDEX_SCAN(no_scan_table public.no_scan_table_pkey)
+ NO_GATHER(no_scan_table)
+(8 rows)
+
+COMMIT;
+-- Conflict: same method required and forbidden; both conflicting, neither applied.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'SEQ_SCAN(no_scan_table) NO_SEQ_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table;
+ QUERY PLAN
+-----------------------------------------------------------------
+ Seq Scan on no_scan_table
+ Supplied Plan Advice:
+ SEQ_SCAN(no_scan_table) /* matched, conflicting */
+ NO_SEQ_SCAN(no_scan_table) /* matched, conflicting, failed */
+ Generated Plan Advice:
+ SEQ_SCAN(no_scan_table)
+ NO_GATHER(no_scan_table)
+(7 rows)
+
+COMMIT;
+-- No conflict: NO_SEQ_SCAN and a positive INDEX_SCAN are compatible.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table) INDEX_SCAN(no_scan_table no_scan_table_pkey)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+ QUERY PLAN
+--------------------------------------------------------------
+ Index Scan using no_scan_table_pkey on no_scan_table
+ Index Cond: (a = 1)
+ Supplied Plan Advice:
+ NO_SEQ_SCAN(no_scan_table) /* matched */
+ INDEX_SCAN(no_scan_table no_scan_table_pkey) /* matched */
+ Generated Plan Advice:
+ INDEX_SCAN(no_scan_table public.no_scan_table_pkey)
+ NO_GATHER(no_scan_table)
+(8 rows)
+
+COMMIT;
+-- Scan tags forbid sublists (simple_target_list): this is a syntax error.
+SET pg_plan_advice.advice = 'NO_SEQ_SCAN((no_scan_table no_scan_table))';
+ERROR: invalid value for parameter "pg_plan_advice.advice": "NO_SEQ_SCAN((no_scan_table no_scan_table))"
+DETAIL: Could not parse advice: syntax error at or near "("
+DROP TABLE no_scan_table;
diff --git a/contrib/pg_plan_advice/pgpa_ast.c b/contrib/pg_plan_advice/pgpa_ast.c
index 01db8d24cd0..02025b61dd3 100644
--- a/contrib/pg_plan_advice/pgpa_ast.c
+++ b/contrib/pg_plan_advice/pgpa_ast.c
@@ -58,8 +58,34 @@ pgpa_cstring_advice_tag(pgpa_advice_tag_type advice_tag)
return "NESTED_LOOP_MEMOIZE";
case PGPA_TAG_NESTED_LOOP_PLAIN:
return "NESTED_LOOP_PLAIN";
+ case PGPA_TAG_NO_BITMAP_HEAP_SCAN:
+ return "NO_BITMAP_HEAP_SCAN";
case PGPA_TAG_NO_GATHER:
return "NO_GATHER";
+ case PGPA_TAG_NO_HASH_JOIN:
+ return "NO_HASH_JOIN";
+ case PGPA_TAG_NO_INDEX_ONLY_SCAN:
+ return "NO_INDEX_ONLY_SCAN";
+ case PGPA_TAG_NO_INDEX_SCAN:
+ return "NO_INDEX_SCAN";
+ case PGPA_TAG_NO_MERGE_JOIN:
+ return "NO_MERGE_JOIN";
+ case PGPA_TAG_NO_MERGE_JOIN_MATERIALIZE:
+ return "NO_MERGE_JOIN_MATERIALIZE";
+ case PGPA_TAG_NO_MERGE_JOIN_PLAIN:
+ return "NO_MERGE_JOIN_PLAIN";
+ case PGPA_TAG_NO_NESTED_LOOP:
+ return "NO_NESTED_LOOP";
+ case PGPA_TAG_NO_NESTED_LOOP_MATERIALIZE:
+ return "NO_NESTED_LOOP_MATERIALIZE";
+ case PGPA_TAG_NO_NESTED_LOOP_MEMOIZE:
+ return "NO_NESTED_LOOP_MEMOIZE";
+ case PGPA_TAG_NO_NESTED_LOOP_PLAIN:
+ return "NO_NESTED_LOOP_PLAIN";
+ case PGPA_TAG_NO_SEQ_SCAN:
+ return "NO_SEQ_SCAN";
+ case PGPA_TAG_NO_TID_SCAN:
+ return "NO_TID_SCAN";
case PGPA_TAG_PARTITIONWISE:
return "PARTITIONWISE";
case PGPA_TAG_SEMIJOIN_NON_UNIQUE:
@@ -135,8 +161,34 @@ pgpa_parse_advice_tag(const char *tag, bool *fail)
return PGPA_TAG_NESTED_LOOP_MEMOIZE;
if (strcmp(tag, "nested_loop_plain") == 0)
return PGPA_TAG_NESTED_LOOP_PLAIN;
+ if (strcmp(tag, "no_bitmap_heap_scan") == 0)
+ return PGPA_TAG_NO_BITMAP_HEAP_SCAN;
if (strcmp(tag, "no_gather") == 0)
return PGPA_TAG_NO_GATHER;
+ if (strcmp(tag, "no_hash_join") == 0)
+ return PGPA_TAG_NO_HASH_JOIN;
+ if (strcmp(tag, "no_index_only_scan") == 0)
+ return PGPA_TAG_NO_INDEX_ONLY_SCAN;
+ if (strcmp(tag, "no_index_scan") == 0)
+ return PGPA_TAG_NO_INDEX_SCAN;
+ if (strcmp(tag, "no_merge_join") == 0)
+ return PGPA_TAG_NO_MERGE_JOIN;
+ if (strcmp(tag, "no_merge_join_materialize") == 0)
+ return PGPA_TAG_NO_MERGE_JOIN_MATERIALIZE;
+ if (strcmp(tag, "no_merge_join_plain") == 0)
+ return PGPA_TAG_NO_MERGE_JOIN_PLAIN;
+ if (strcmp(tag, "no_nested_loop") == 0)
+ return PGPA_TAG_NO_NESTED_LOOP;
+ if (strcmp(tag, "no_nested_loop_materialize") == 0)
+ return PGPA_TAG_NO_NESTED_LOOP_MATERIALIZE;
+ if (strcmp(tag, "no_nested_loop_memoize") == 0)
+ return PGPA_TAG_NO_NESTED_LOOP_MEMOIZE;
+ if (strcmp(tag, "no_nested_loop_plain") == 0)
+ return PGPA_TAG_NO_NESTED_LOOP_PLAIN;
+ if (strcmp(tag, "no_seq_scan") == 0)
+ return PGPA_TAG_NO_SEQ_SCAN;
+ if (strcmp(tag, "no_tid_scan") == 0)
+ return PGPA_TAG_NO_TID_SCAN;
break;
case 'p':
if (strcmp(tag, "partitionwise") == 0)
diff --git a/contrib/pg_plan_advice/pgpa_ast.h b/contrib/pg_plan_advice/pgpa_ast.h
index 4bd6ffa5e3a..c18fc164abc 100644
--- a/contrib/pg_plan_advice/pgpa_ast.h
+++ b/contrib/pg_plan_advice/pgpa_ast.h
@@ -93,7 +93,20 @@ typedef enum pgpa_advice_tag_type
PGPA_TAG_NESTED_LOOP_MATERIALIZE,
PGPA_TAG_NESTED_LOOP_MEMOIZE,
PGPA_TAG_NESTED_LOOP_PLAIN,
+ PGPA_TAG_NO_BITMAP_HEAP_SCAN,
PGPA_TAG_NO_GATHER,
+ PGPA_TAG_NO_HASH_JOIN,
+ PGPA_TAG_NO_INDEX_ONLY_SCAN,
+ PGPA_TAG_NO_INDEX_SCAN,
+ PGPA_TAG_NO_MERGE_JOIN,
+ PGPA_TAG_NO_MERGE_JOIN_MATERIALIZE,
+ PGPA_TAG_NO_MERGE_JOIN_PLAIN,
+ PGPA_TAG_NO_NESTED_LOOP,
+ PGPA_TAG_NO_NESTED_LOOP_MATERIALIZE,
+ PGPA_TAG_NO_NESTED_LOOP_MEMOIZE,
+ PGPA_TAG_NO_NESTED_LOOP_PLAIN,
+ PGPA_TAG_NO_SEQ_SCAN,
+ PGPA_TAG_NO_TID_SCAN,
PGPA_TAG_PARTITIONWISE,
PGPA_TAG_SEMIJOIN_NON_UNIQUE,
PGPA_TAG_SEMIJOIN_UNIQUE,
diff --git a/contrib/pg_plan_advice/pgpa_parser.y b/contrib/pg_plan_advice/pgpa_parser.y
index 5811a6e5e56..38684bef727 100644
--- a/contrib/pg_plan_advice/pgpa_parser.y
+++ b/contrib/pg_plan_advice/pgpa_parser.y
@@ -108,8 +108,18 @@ advice_item: TOK_TAG_JOIN_ORDER '(' join_order_target_list ')'
$$->tag = PGPA_TAG_BITMAP_HEAP_SCAN;
else if (strcmp($1, "do_not_scan") == 0)
$$->tag = PGPA_TAG_DO_NOT_SCAN;
+ else if (strcmp($1, "no_bitmap_heap_scan") == 0)
+ $$->tag = PGPA_TAG_NO_BITMAP_HEAP_SCAN;
else if (strcmp($1, "no_gather") == 0)
$$->tag = PGPA_TAG_NO_GATHER;
+ else if (strcmp($1, "no_index_only_scan") == 0)
+ $$->tag = PGPA_TAG_NO_INDEX_ONLY_SCAN;
+ else if (strcmp($1, "no_index_scan") == 0)
+ $$->tag = PGPA_TAG_NO_INDEX_SCAN;
+ else if (strcmp($1, "no_seq_scan") == 0)
+ $$->tag = PGPA_TAG_NO_SEQ_SCAN;
+ else if (strcmp($1, "no_tid_scan") == 0)
+ $$->tag = PGPA_TAG_NO_TID_SCAN;
else if (strcmp($1, "seq_scan") == 0)
$$->tag = PGPA_TAG_SEQ_SCAN;
else if (strcmp($1, "tid_scan") == 0)
diff --git a/contrib/pg_plan_advice/pgpa_planner.c b/contrib/pg_plan_advice/pgpa_planner.c
index b3329b793aa..a29500e0e1d 100644
--- a/contrib/pg_plan_advice/pgpa_planner.c
+++ b/contrib/pg_plan_advice/pgpa_planner.c
@@ -155,6 +155,9 @@ static bool pgpa_semijoin_permits_join(int outer_count, int inner_count,
bool outer_is_nullable,
bool *restrict_method);
+static uint64 pgpa_no_join_mask_from_advice_tag(pgpa_advice_tag_type tag);
+static uint64 pgpa_no_scan_mask_from_advice_tag(pgpa_advice_tag_type tag);
+
static List *pgpa_planner_append_feedback(List *list, pgpa_trove *trove,
pgpa_trove_lookup_type type,
pgpa_identifier *rt_identifiers,
@@ -947,8 +950,12 @@ pgpa_planner_apply_join_path_advice(JoinType jointype, uint64 *pgs_mask_p,
Bitmapset *jo_deny_indexes = NULL;
Bitmapset *jo_deny_rel_indexes = NULL;
Bitmapset *jm_indexes = NULL;
- bool jm_conflict = false;
+ bool jm_pos_conflict = false; /* positive tags disagree */
+ bool jm_pos_neg_conflict = false; /* a positive method is
+ * forbidden */
uint64 join_mask = 0;
+ Bitmapset *no_jm_indexes = NULL;
+ uint64 no_join_mask = 0;
Bitmapset *sj_permit_indexes = NULL;
Bitmapset *sj_deny_indexes = NULL;
@@ -1043,12 +1050,43 @@ pgpa_planner_apply_join_path_advice(JoinType jointype, uint64 *pgs_mask_p,
{
jm_indexes = bms_add_member(jm_indexes, i);
if (join_mask != 0 && join_mask != my_join_mask)
- jm_conflict = true;
+ jm_pos_conflict = true;
join_mask = my_join_mask;
}
continue;
}
+ /* Handle NO_ join method advice. */
+ {
+ uint64 my_no_join_mask;
+
+ my_no_join_mask = pgpa_no_join_mask_from_advice_tag(entry->tag);
+ if (my_no_join_mask != 0)
+ {
+ bool permit;
+ bool restrict_method;
+
+ /*
+ * NO_ join tags impose the same join-order constraint as
+ * positive ones: the target must be the inner rel. Reuse
+ * pgpa_join_method_permits_join to enforce it.
+ */
+ permit = pgpa_join_method_permits_join(pjs->outer_count,
+ pjs->inner_count,
+ pjs->rids,
+ entry,
+ &restrict_method);
+ if (!permit)
+ jo_deny_indexes = bms_add_member(jo_deny_indexes, i);
+ else if (restrict_method)
+ {
+ no_jm_indexes = bms_add_member(no_jm_indexes, i);
+ no_join_mask |= my_no_join_mask;
+ }
+ continue;
+ }
+ }
+
/* Handle semijoin uniqueness advice. */
if (entry->tag == PGPA_TAG_SEMIJOIN_UNIQUE ||
entry->tag == PGPA_TAG_SEMIJOIN_NON_UNIQUE)
@@ -1118,13 +1156,26 @@ pgpa_planner_apply_join_path_advice(JoinType jointype, uint64 *pgs_mask_p,
}
/*
- * If more than one join method specification is relevant here and they
- * differ, mark them all as conflicting.
+ * If more than one positive join method specification is relevant here
+ * and they differ, mark them all as conflicting.
*/
- if (jm_conflict)
+ if (jm_pos_conflict)
pgpa_trove_set_flags(pjs->join_entries, jm_indexes,
PGPA_FB_CONFLICTING);
+ /*
+ * Detect positive-vs-negative join method conflict: a method both
+ * required by a positive tag and forbidden by a NO_ tag.
+ */
+ if ((join_mask & no_join_mask) != 0)
+ {
+ jm_pos_neg_conflict = true;
+ pgpa_trove_set_flags(pjs->join_entries, jm_indexes,
+ PGPA_FB_CONFLICTING);
+ pgpa_trove_set_flags(pjs->join_entries, no_jm_indexes,
+ PGPA_FB_CONFLICTING);
+ }
+
/* If semijoin advice says both yes and no, mark it all as conflicting. */
if (sj_permit_indexes != NULL && sj_deny_indexes != NULL)
{
@@ -1143,18 +1194,18 @@ pgpa_planner_apply_join_path_advice(JoinType jointype, uint64 *pgs_mask_p,
if ((jo_deny_indexes != NULL || jo_deny_rel_indexes != NULL) &&
jo_permit_indexes == NULL)
*pgs_mask_p &= ~PGS_JOIN_ANY;
- if (join_mask != 0 && !jm_conflict)
+ if (join_mask != 0 && !jm_pos_conflict && !jm_pos_neg_conflict)
*pgs_mask_p &= ~(PGS_JOIN_ANY & ~join_mask);
+ if (no_join_mask != 0 && !jm_pos_neg_conflict)
+ *pgs_mask_p &= ~no_join_mask;
if (sj_deny_indexes != NULL && sj_permit_indexes == NULL)
*pgs_mask_p &= ~PGS_JOIN_ANY;
}
/*
- * Translate an advice tag into a path generation strategy mask.
+ * Translate a positive join advice tag into a strategy mask to enforce.
*
- * This function can be called with tag types that don't represent join
- * strategies. In such cases, we just return 0, which can't be confused with
- * a valid mask.
+ * Returns 0 for tags that don't represent (positive) join strategies.
*/
static uint64
pgpa_join_strategy_mask_from_advice_tag(pgpa_advice_tag_type tag)
@@ -1180,6 +1231,37 @@ pgpa_join_strategy_mask_from_advice_tag(pgpa_advice_tag_type tag)
}
}
+/*
+ * Translate a NO_ join advice tag into a strategy mask to forbid.
+ *
+ * Returns 0 for tags that aren't NO_ join tags.
+ */
+static uint64
+pgpa_no_join_mask_from_advice_tag(pgpa_advice_tag_type tag)
+{
+ switch (tag)
+ {
+ case PGPA_TAG_NO_HASH_JOIN:
+ return PGS_HASHJOIN;
+ case PGPA_TAG_NO_MERGE_JOIN:
+ return PGS_MERGEJOIN_ANY;
+ case PGPA_TAG_NO_MERGE_JOIN_MATERIALIZE:
+ return PGS_MERGEJOIN_MATERIALIZE;
+ case PGPA_TAG_NO_MERGE_JOIN_PLAIN:
+ return PGS_MERGEJOIN_PLAIN;
+ case PGPA_TAG_NO_NESTED_LOOP:
+ return PGS_NESTLOOP_ANY;
+ case PGPA_TAG_NO_NESTED_LOOP_MATERIALIZE:
+ return PGS_NESTLOOP_MATERIALIZE;
+ case PGPA_TAG_NO_NESTED_LOOP_MEMOIZE:
+ return PGS_NESTLOOP_MEMOIZE;
+ case PGPA_TAG_NO_NESTED_LOOP_PLAIN:
+ return PGS_NESTLOOP_PLAIN;
+ default:
+ return 0;
+ }
+}
+
/*
* Does a certain item of join order advice permit a certain join?
*
@@ -1619,6 +1701,31 @@ pgpa_semijoin_permits_join(int outer_count, int inner_count,
return false;
}
+/*
+ * Translate a NO_ scan advice tag into a strategy mask to forbid.
+ *
+ * Returns 0 for tags that aren't NO_ scan tags.
+ */
+static uint64
+pgpa_no_scan_mask_from_advice_tag(pgpa_advice_tag_type tag)
+{
+ switch (tag)
+ {
+ case PGPA_TAG_NO_BITMAP_HEAP_SCAN:
+ return PGS_BITMAPSCAN;
+ case PGPA_TAG_NO_INDEX_ONLY_SCAN:
+ return PGS_INDEXONLYSCAN | PGS_CONSIDER_INDEXONLY;
+ case PGPA_TAG_NO_INDEX_SCAN:
+ return PGS_INDEXSCAN;
+ case PGPA_TAG_NO_SEQ_SCAN:
+ return PGS_SEQSCAN;
+ case PGPA_TAG_NO_TID_SCAN:
+ return PGS_TIDSCAN;
+ default:
+ return 0;
+ }
+}
+
/*
* Apply scan advice to a RelOptInfo.
*/
@@ -1637,19 +1744,36 @@ pgpa_planner_apply_scan_advice(RelOptInfo *rel,
int i = -1;
pgpa_trove_entry *scan_entry = NULL;
int flags;
- bool scan_type_conflict = false;
+ bool scan_pos_conflict = false; /* positive tags disagree */
+ bool scan_pos_neg_conflict = false; /* a positive method is
+ * forbidden */
Bitmapset *scan_type_indexes = NULL;
Bitmapset *scan_type_rel_indexes = NULL;
+ Bitmapset *no_scan_indexes = NULL;
uint64 gather_mask = 0;
uint64 scan_type = all_scan_mask; /* sentinel: no advice yet */
+ uint64 no_scan_mask = 0;
/* Scrutinize available scan advice. */
while ((i = bms_next_member(scan_indexes, i)) >= 0)
{
pgpa_trove_entry *my_entry = &scan_entries[i];
uint64 my_scan_type = all_scan_mask;
+ uint64 my_no_scan_mask;
+
+ /*
+ * NO_ scan tags just accumulate a set of forbidden methods; handle
+ * them separately from the positive scan-type logic below.
+ */
+ my_no_scan_mask = pgpa_no_scan_mask_from_advice_tag(my_entry->tag);
+ if (my_no_scan_mask != 0)
+ {
+ no_scan_mask |= my_no_scan_mask;
+ no_scan_indexes = bms_add_member(no_scan_indexes, i);
+ continue;
+ }
- /* Translate our advice tags to a scan strategy advice value. */
+ /* Translate positive advice tags to a scan strategy value. */
if (my_entry->tag == PGPA_TAG_DO_NOT_SCAN)
my_scan_type = 0;
else if (my_entry->tag == PGPA_TAG_BITMAP_HEAP_SCAN)
@@ -1690,19 +1814,27 @@ pgpa_planner_apply_scan_advice(RelOptInfo *rel,
if (my_scan_type != all_scan_mask)
{
if (scan_type != all_scan_mask && scan_type != my_scan_type)
- scan_type_conflict = true;
- if (!scan_type_conflict && scan_entry != NULL &&
+ scan_pos_conflict = true;
+ if (!scan_pos_conflict && scan_entry != NULL &&
my_entry->target->itarget != NULL &&
scan_entry->target->itarget != NULL &&
!pgpa_index_targets_equal(scan_entry->target->itarget,
my_entry->target->itarget))
- scan_type_conflict = true;
+ scan_pos_conflict = true;
scan_entry = my_entry;
scan_type = my_scan_type;
scan_type_indexes = bms_add_member(scan_type_indexes, i);
}
}
+ /*
+ * Detect positive-vs-negative scan conflict: a positive scan type that is
+ * simultaneously forbidden by a NO_ tag. Two NO_ tags for different
+ * methods are never in conflict with each other.
+ */
+ if (scan_type != all_scan_mask && (scan_type & no_scan_mask) != 0)
+ scan_pos_neg_conflict = true;
+
/* Scrutinize available gather-related and partitionwise advice. */
i = -1;
while ((i = bms_next_member(rel_indexes, i)) >= 0)
@@ -1725,7 +1857,7 @@ pgpa_planner_apply_scan_advice(RelOptInfo *rel,
const uint64 my_scan_type = PGS_APPEND | PGS_MERGE_APPEND;
if (scan_type != all_scan_mask && scan_type != my_scan_type)
- scan_type_conflict = true;
+ scan_pos_conflict = true;
scan_entry = my_entry;
scan_type = my_scan_type;
scan_type_rel_indexes =
@@ -1778,7 +1910,7 @@ pgpa_planner_apply_scan_advice(RelOptInfo *rel,
}
/* Enforce choice of index. */
- if (scan_entry != NULL && !scan_type_conflict &&
+ if (scan_entry != NULL && !scan_pos_conflict &&
(scan_entry->tag == PGPA_TAG_INDEX_SCAN ||
scan_entry->tag == PGPA_TAG_INDEX_ONLY_SCAN))
{
@@ -1822,14 +1954,24 @@ pgpa_planner_apply_scan_advice(RelOptInfo *rel,
/*
* Mark all the scan method entries as fully matched; and if they specify
- * different things, mark them all as conflicting.
+ * different things, mark them all as conflicting. Also mark them as
+ * conflicting if any NO_ tag forbids the requested scan method.
*/
flags = PGPA_FB_MATCH_PARTIAL | PGPA_FB_MATCH_FULL;
- if (scan_type_conflict)
+ if (scan_pos_conflict || scan_pos_neg_conflict)
flags |= PGPA_FB_CONFLICTING;
pgpa_trove_set_flags(scan_entries, scan_type_indexes, flags);
pgpa_trove_set_flags(rel_entries, scan_type_rel_indexes, flags);
+ /*
+ * Mark NO_ scan entries as fully matched. Also mark them as conflicting
+ * when a positive tag requests the same scan method.
+ */
+ flags = PGPA_FB_MATCH_PARTIAL | PGPA_FB_MATCH_FULL;
+ if (scan_pos_neg_conflict)
+ flags |= PGPA_FB_CONFLICTING;
+ pgpa_trove_set_flags(scan_entries, no_scan_indexes, flags);
+
/*
* Mark every Gather-related piece of advice as partially matched. Mark
* the ones that included this relation as a target by itself as fully
@@ -1847,8 +1989,10 @@ pgpa_planner_apply_scan_advice(RelOptInfo *rel,
* Only clear bits here, so that we still respect the enable_* GUCs. Do
* nothing in cases where the advice on a single topic conflicts.
*/
- if (scan_type != all_scan_mask && !scan_type_conflict)
+ if (scan_type != all_scan_mask && !scan_pos_conflict && !scan_pos_neg_conflict)
rel->pgs_mask &= ~(all_scan_mask & ~scan_type);
+ if (no_scan_mask != 0 && !scan_pos_neg_conflict)
+ rel->pgs_mask &= ~(all_scan_mask & no_scan_mask);
if (gather_mask != 0 && !gather_conflict)
{
uint64 all_gather_mask;
diff --git a/contrib/pg_plan_advice/pgpa_scanner.l b/contrib/pg_plan_advice/pgpa_scanner.l
index e6d60f57e1e..fc8929e31dd 100644
--- a/contrib/pg_plan_advice/pgpa_scanner.l
+++ b/contrib/pg_plan_advice/pgpa_scanner.l
@@ -129,7 +129,12 @@ xcinside [^*/]+
tag == PGPA_TAG_TID_SCAN ||
tag == PGPA_TAG_BITMAP_HEAP_SCAN ||
tag == PGPA_TAG_NO_GATHER ||
- tag == PGPA_TAG_DO_NOT_SCAN)
+ tag == PGPA_TAG_DO_NOT_SCAN ||
+ tag == PGPA_TAG_NO_SEQ_SCAN ||
+ tag == PGPA_TAG_NO_TID_SCAN ||
+ tag == PGPA_TAG_NO_BITMAP_HEAP_SCAN ||
+ tag == PGPA_TAG_NO_INDEX_SCAN ||
+ tag == PGPA_TAG_NO_INDEX_ONLY_SCAN)
return TOK_TAG_SIMPLE;
else
return TOK_TAG_GENERIC;
diff --git a/contrib/pg_plan_advice/pgpa_trove.c b/contrib/pg_plan_advice/pgpa_trove.c
index ca69f3bd3df..abe10363d3e 100644
--- a/contrib/pg_plan_advice/pgpa_trove.c
+++ b/contrib/pg_plan_advice/pgpa_trove.c
@@ -166,6 +166,11 @@ pgpa_build_trove(List *advice_items)
case PGPA_TAG_DO_NOT_SCAN:
case PGPA_TAG_INDEX_ONLY_SCAN:
case PGPA_TAG_INDEX_SCAN:
+ case PGPA_TAG_NO_BITMAP_HEAP_SCAN:
+ case PGPA_TAG_NO_INDEX_ONLY_SCAN:
+ case PGPA_TAG_NO_INDEX_SCAN:
+ case PGPA_TAG_NO_SEQ_SCAN:
+ case PGPA_TAG_NO_TID_SCAN:
case PGPA_TAG_SEQ_SCAN:
case PGPA_TAG_TID_SCAN:
@@ -192,6 +197,14 @@ pgpa_build_trove(List *advice_items)
case PGPA_TAG_NESTED_LOOP_MATERIALIZE:
case PGPA_TAG_NESTED_LOOP_MEMOIZE:
case PGPA_TAG_NESTED_LOOP_PLAIN:
+ case PGPA_TAG_NO_HASH_JOIN:
+ case PGPA_TAG_NO_MERGE_JOIN:
+ case PGPA_TAG_NO_MERGE_JOIN_MATERIALIZE:
+ case PGPA_TAG_NO_MERGE_JOIN_PLAIN:
+ case PGPA_TAG_NO_NESTED_LOOP:
+ case PGPA_TAG_NO_NESTED_LOOP_MATERIALIZE:
+ case PGPA_TAG_NO_NESTED_LOOP_MEMOIZE:
+ case PGPA_TAG_NO_NESTED_LOOP_PLAIN:
case PGPA_TAG_SEMIJOIN_NON_UNIQUE:
case PGPA_TAG_SEMIJOIN_UNIQUE:
diff --git a/contrib/pg_plan_advice/pgpa_walker.c b/contrib/pg_plan_advice/pgpa_walker.c
index e49361ae266..89052e90707 100644
--- a/contrib/pg_plan_advice/pgpa_walker.c
+++ b/contrib/pg_plan_advice/pgpa_walker.c
@@ -894,6 +894,77 @@ pgpa_walker_would_advise(pgpa_plan_walker_context *walker,
relids);
case PGPA_TAG_NO_GATHER:
return pgpa_walker_contains_no_gather(walker, relids);
+
+ /*
+ * For NO_ scan tags, the advice is satisfied when the plan does
+ * NOT use the forbidden scan strategy.
+ */
+ case PGPA_TAG_NO_SEQ_SCAN:
+ return pgpa_walker_find_scan(walker,
+ PGPA_SCAN_SEQ,
+ relids) == NULL;
+ case PGPA_TAG_NO_BITMAP_HEAP_SCAN:
+ return pgpa_walker_find_scan(walker,
+ PGPA_SCAN_BITMAP_HEAP,
+ relids) == NULL;
+ case PGPA_TAG_NO_INDEX_SCAN:
+ return pgpa_walker_find_scan(walker,
+ PGPA_SCAN_INDEX,
+ relids) == NULL;
+ case PGPA_TAG_NO_INDEX_ONLY_SCAN:
+ return pgpa_walker_find_scan(walker,
+ PGPA_SCAN_INDEX_ONLY,
+ relids) == NULL;
+ case PGPA_TAG_NO_TID_SCAN:
+ return pgpa_walker_find_scan(walker,
+ PGPA_SCAN_TID,
+ relids) == NULL;
+
+ /*
+ * For NO_ join tags, the advice is satisfied when the plan does
+ * NOT use any of the forbidden join strategies.
+ */
+ case PGPA_TAG_NO_HASH_JOIN:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_HASH_JOIN,
+ relids);
+ case PGPA_TAG_NO_MERGE_JOIN:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_MERGE_JOIN_PLAIN,
+ relids) &&
+ !pgpa_walker_contains_join(walker,
+ JSTRAT_MERGE_JOIN_MATERIALIZE,
+ relids);
+ case PGPA_TAG_NO_MERGE_JOIN_MATERIALIZE:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_MERGE_JOIN_MATERIALIZE,
+ relids);
+ case PGPA_TAG_NO_MERGE_JOIN_PLAIN:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_MERGE_JOIN_PLAIN,
+ relids);
+ case PGPA_TAG_NO_NESTED_LOOP:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_NESTED_LOOP_PLAIN,
+ relids) &&
+ !pgpa_walker_contains_join(walker,
+ JSTRAT_NESTED_LOOP_MATERIALIZE,
+ relids) &&
+ !pgpa_walker_contains_join(walker,
+ JSTRAT_NESTED_LOOP_MEMOIZE,
+ relids);
+ case PGPA_TAG_NO_NESTED_LOOP_MATERIALIZE:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_NESTED_LOOP_MATERIALIZE,
+ relids);
+ case PGPA_TAG_NO_NESTED_LOOP_MEMOIZE:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_NESTED_LOOP_MEMOIZE,
+ relids);
+ case PGPA_TAG_NO_NESTED_LOOP_PLAIN:
+ return !pgpa_walker_contains_join(walker,
+ JSTRAT_NESTED_LOOP_PLAIN,
+ relids);
}
/* should not get here */
diff --git a/contrib/pg_plan_advice/sql/no_join.sql b/contrib/pg_plan_advice/sql/no_join.sql
new file mode 100644
index 00000000000..19a9acc99fe
--- /dev/null
+++ b/contrib/pg_plan_advice/sql/no_join.sql
@@ -0,0 +1,92 @@
+LOAD 'pg_plan_advice';
+SET max_parallel_workers_per_gather = 0;
+
+CREATE TABLE no_join_dim (id serial primary key, dim text)
+ WITH (autovacuum_enabled = false);
+INSERT INTO no_join_dim (dim) SELECT random()::text FROM generate_series(1,100) g;
+VACUUM ANALYZE no_join_dim;
+
+CREATE TABLE no_join_fact (
+ id int primary key,
+ dim_id integer not null references no_join_dim (id)
+) WITH (autovacuum_enabled = false);
+INSERT INTO no_join_fact
+ SELECT g, (g%3)+1 FROM generate_series(1,100000) g;
+CREATE INDEX no_join_fact_dim_id ON no_join_fact (dim_id);
+VACUUM ANALYZE no_join_fact;
+
+-- Baseline: hash join with d on the inner side.
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+
+-- NO_HASH_JOIN(d): d stays inner, planner falls back to another method.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+-- NO_HASH_JOIN(f): the join-order constraint forces f to the inner side.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+-- NO_NESTED_LOOP(f): f forced inner, all NL variants forbidden -> merge join.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+-- NO_MERGE_JOIN(d): d already inner, hash join still allowed -> plan unchanged.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_MERGE_JOIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+-- Stacking: NO_HASH_JOIN(f) + NO_NESTED_LOOP(f) leaves only merge join.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(f) NO_NESTED_LOOP(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+-- Specific NO_ variants targeting d, already the inner side: forbidding any one
+-- NL or merge variant leaves hash join available, so the plan is unchanged.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP_PLAIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP_MEMOIZE(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+SET LOCAL pg_plan_advice.advice = 'NO_NESTED_LOOP_MATERIALIZE(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+SET LOCAL pg_plan_advice.advice = 'NO_MERGE_JOIN_PLAIN(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+SET LOCAL pg_plan_advice.advice = 'NO_MERGE_JOIN_MATERIALIZE(d)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+-- Conflict: same method required and forbidden; both marked conflicting.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'HASH_JOIN(f) NO_HASH_JOIN(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+-- No conflict: NO_HASH_JOIN(f) and a positive tag for a different method.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_HASH_JOIN(f) NESTED_LOOP_PLAIN(f)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_join_fact f JOIN no_join_dim d ON f.dim_id = d.id;
+COMMIT;
+
+DROP TABLE no_join_fact;
+DROP TABLE no_join_dim;
diff --git a/contrib/pg_plan_advice/sql/no_scan.sql b/contrib/pg_plan_advice/sql/no_scan.sql
new file mode 100644
index 00000000000..b189ef73440
--- /dev/null
+++ b/contrib/pg_plan_advice/sql/no_scan.sql
@@ -0,0 +1,88 @@
+LOAD 'pg_plan_advice';
+SET max_parallel_workers_per_gather = 0;
+SET seq_page_cost = 0.1;
+SET random_page_cost = 0.1;
+SET cpu_tuple_cost = 0;
+SET cpu_index_tuple_cost = 0;
+
+CREATE TABLE no_scan_table (a int primary key, b text)
+ WITH (autovacuum_enabled = false);
+INSERT INTO no_scan_table
+ SELECT g, 'some text ' || g FROM generate_series(1, 100000) g;
+VACUUM ANALYZE no_scan_table;
+
+-- Baselines without advice: seq scan for a full read, index scan for a lookup.
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table;
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+
+-- NO_SEQ_SCAN with no indexable qual: no alternative, so the advice fails.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table;
+COMMIT;
+
+-- NO_SEQ_SCAN with an indexable qual: falls back to index scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+COMMIT;
+
+-- NO_INDEX_SCAN: falls back to bitmap heap scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_INDEX_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+COMMIT;
+
+-- NO_INDEX_ONLY_SCAN: falls back to a plain index scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_INDEX_ONLY_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT a FROM no_scan_table WHERE a = 1;
+COMMIT;
+
+-- NO_BITMAP_HEAP_SCAN: with only a BRIN index available, falls back to seq scan.
+CREATE INDEX no_scan_table_b ON no_scan_table USING brin (b);
+VACUUM ANALYZE no_scan_table;
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_BITMAP_HEAP_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE b > 'some text 8';
+COMMIT;
+
+-- NO_TID_SCAN: falls back to seq scan.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_TID_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE ctid = '(0,1)';
+COMMIT;
+
+-- Multiple NO_ scan tags stack without conflict.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table) NO_BITMAP_HEAP_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+COMMIT;
+
+-- Conflict: same method required and forbidden; both conflicting, neither applied.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'SEQ_SCAN(no_scan_table) NO_SEQ_SCAN(no_scan_table)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table;
+COMMIT;
+
+-- No conflict: NO_SEQ_SCAN and a positive INDEX_SCAN are compatible.
+BEGIN;
+SET LOCAL pg_plan_advice.advice = 'NO_SEQ_SCAN(no_scan_table) INDEX_SCAN(no_scan_table no_scan_table_pkey)';
+EXPLAIN (COSTS OFF, PLAN_ADVICE)
+ SELECT * FROM no_scan_table WHERE a = 1;
+COMMIT;
+
+-- Scan tags forbid sublists (simple_target_list): this is a syntax error.
+SET pg_plan_advice.advice = 'NO_SEQ_SCAN((no_scan_table no_scan_table))';
+
+DROP TABLE no_scan_table;
diff --git a/doc/src/sgml/pgplanadvice.sgml b/doc/src/sgml/pgplanadvice.sgml
index b1395ec951e..dff6594a54b 100644
--- a/doc/src/sgml/pgplanadvice.sgml
+++ b/doc/src/sgml/pgplanadvice.sgml
@@ -320,6 +320,58 @@ DO_NOT_SCAN(<replaceable>target</replaceable> [ ... ])</synopsis>
</sect3>
+ <sect3 id="pgplanadvice-no-scan-method">
+ <title>Negative Scan Method Advice</title>
+ <synopsis>
+NO_SEQ_SCAN(<replaceable>target</replaceable> [ ... ])
+NO_TID_SCAN(<replaceable>target</replaceable> [ ... ])
+NO_INDEX_SCAN(<replaceable>target</replaceable> [ ... ])
+NO_INDEX_ONLY_SCAN(<replaceable>target</replaceable> [ ... ])
+NO_BITMAP_HEAP_SCAN(<replaceable>target</replaceable> [ ... ])</synopsis>
+
+ <para>
+ These tags are the negative counterparts of the positive scan method tags.
+ Each <literal>NO_</literal> tag forbids the corresponding scan method for
+ the specified relation or relations. The planner will choose any other
+ eligible scan method instead.
+ </para>
+
+ <para>
+ For example, <literal>NO_SEQ_SCAN(t)</literal> tells the planner not to
+ use a <literal>Seq Scan</literal> on <literal>t</literal>. If the only
+ viable alternative is an index scan, the planner will use that. If no
+ alternative is available, the plan still uses the forbidden method and the
+ advice is reported as <literal>failed</literal>.
+ </para>
+
+ <para>
+ Unlike the positive scan method tags, multiple negative scan method tags
+ for the same relation can be combined freely without conflict. For example,
+ <literal>NO_SEQ_SCAN(t) NO_BITMAP_HEAP_SCAN(t)</literal> is valid and
+ restricts the planner to use an index scan or TID scan on <literal>t</literal>.
+ </para>
+
+ <para>
+ A negative tag and a positive tag specifying the same method are in
+ conflict with each other. For example, <literal>SEQ_SCAN(t)
+ NO_SEQ_SCAN(t)</literal> is a contradiction, and both pieces of advice will
+ be marked <literal>conflicting</literal>. However, a negative tag for one
+ method does not conflict with a positive tag for a different method. For
+ instance, <literal>NO_SEQ_SCAN(t) INDEX_SCAN(t my_index)</literal> is not a
+ conflict: the index scan is enforced and the prohibition on sequential scans
+ is also satisfied.
+ </para>
+
+ <para>
+ Note that <literal>NO_SEQ_SCAN((x y))</literal> and similar forms with a
+ parenthesized sublist are not valid syntax for negative scan tags, because
+ scan methods apply to individual relations, not join products. Negative scan
+ tags use the same target syntax as their positive counterparts: a
+ flat list of relation identifiers.
+ </para>
+
+ </sect3>
+
<sect3 id="pgplanadvice-join-order">
<title>Join Order Advice</title>
<synopsis>
@@ -433,6 +485,83 @@ join_method_name(<replaceable>join_method_item</replaceable> [ ... ])
</sect3>
+ <sect3 id="pgplanadvice-no-join-method">
+ <title>Negative Join Method Advice</title>
+ <synopsis>
+no_join_method_name(<replaceable>join_method_item</replaceable> [ ... ])
+
+<phrase>where <replaceable>no_join_method_name</replaceable> is:</phrase>
+
+{ NO_HASH_JOIN |
+ NO_NESTED_LOOP | NO_NESTED_LOOP_PLAIN | NO_NESTED_LOOP_MATERIALIZE | NO_NESTED_LOOP_MEMOIZE |
+ NO_MERGE_JOIN | NO_MERGE_JOIN_PLAIN | NO_MERGE_JOIN_MATERIALIZE }
+
+<phrase>and <replaceable>join_method_item</replaceable> is:</phrase>
+
+{ <replaceable>advice_target</replaceable> |
+( <replaceable>advice_target</replaceable> [ ... ] ) }</synopsis>
+
+ <para>
+ These tags are the negative counterparts of the positive join method tags.
+ A negative join method tag specifies that the named join method (or family
+ of join methods) should <emphasis>not</emphasis> be used when the specified
+ relation or set of relations appears on the inner side of a join. The
+ planner will choose any other eligible join method instead.
+ </para>
+
+ <para>
+ Both a coarser group form and a finer specific form are available for
+ nested-loop and merge-join. <literal>NO_NESTED_LOOP(t)</literal> disables
+ all three nested-loop variants (<literal>NESTED_LOOP_PLAIN</literal>,
+ <literal>NESTED_LOOP_MATERIALIZE</literal>, and
+ <literal>NESTED_LOOP_MEMOIZE</literal>), while
+ <literal>NO_NESTED_LOOP_PLAIN(t)</literal> disables only the plain variant,
+ leaving the other two available. Similarly,
+ <literal>NO_MERGE_JOIN(t)</literal> disables both merge-join variants, while
+ <literal>NO_MERGE_JOIN_PLAIN(t)</literal> and
+ <literal>NO_MERGE_JOIN_MATERIALIZE(t)</literal> target individual variants.
+ <literal>NO_HASH_JOIN</literal> has only one form since there is only one
+ hash-join variant.
+ </para>
+
+ <para>
+ Like positive join method tags, negative join method tags accept
+ parenthesized sublists specifying a set of relations that should appear
+ together on the inner side. For example,
+ <literal>NO_HASH_JOIN((a b))</literal> means that the join product of
+ <literal>a</literal> and <literal>b</literal> should not appear together on
+ the inner side of a hash join.
+ </para>
+
+ <para>
+ Negative join method tags impose the same join-order constraint as their
+ positive counterparts: the specified relation (or join product) cannot
+ become the driving table. For example, <literal>NO_HASH_JOIN(t)</literal>
+ implies that <literal>t</literal> cannot be the outermost relation in the
+ join, exactly as <literal>HASH_JOIN(t)</literal> would. Think of
+ <literal>NO_HASH_JOIN(t)</literal> as saying
+ <quote>use anything but a hash join, but keep <literal>t</literal> on the
+ inner side.</quote>
+ </para>
+
+ <para>
+ Multiple negative join method tags for the same relation can be combined
+ freely. For example, <literal>NO_HASH_JOIN(t) NO_NESTED_LOOP(t)</literal>
+ restricts the planner to merge-join when <literal>t</literal> is on the
+ inner side. A negative tag for one method does not conflict with a positive
+ tag for a different method: <literal>NO_HASH_JOIN(t)
+ NESTED_LOOP_PLAIN(t)</literal> is not a conflict.
+ </para>
+
+ <para>
+ A negative tag and a positive tag specifying the same join method are in
+ conflict. For example, <literal>HASH_JOIN(t) NO_HASH_JOIN(t)</literal>
+ contradicts itself, and both entries will be marked
+ <literal>conflicting</literal>.
+ </para>
+
+ </sect3>
+
<sect3 id="pgplanadvice-partitionwise">
<title>Partitionwise Advice</title>
<synopsis>
--
2.45.1