From c05268e6ec931724282b5780f228e5a1aad94268 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 29 Jan 2025 15:31:55 -0500 Subject: [PATCH] Handle default NULL insertion a little better. If a column is omitted in an INSERT, and there's no column default, the code in preptlist.c generates a NULL Const to be inserted. Furthermore, if the column is of a domain type, we wrap the Const in CoerceToDomain, so as to throw a run-time error if the domain has a NOT NULL constraint. That's fine as far as it goes, but there are two problems: 1. We're being sloppy about the type/typmod that the Const is labeled with. It really should have the domain's base type/typmod, since it's the input to CoerceToDomain not the output. This can result in coerce_to_domain inserting a useless length-coercion function (useless because it's being applied to a null). The coercion would typically get const-folded away later, but it'd be better not to create it in the first place. 2. We're not applying expression preprocessing (specifically, eval_const_expressions) to the resulting expression tree. The planner's primary expression-preprocessing pass already happened, so that means the length coercion step and CoerceToDomain node miss preprocessing altogether. This is at the least inefficient, since it means the length coercion and CoerceToDomain will actually be executed for each inserted row, though they could be const-folded away in most cases. Worse, it seems possible that missing preprocessing for the length coercion could result in an invalid plan (for example, due to failing to perform default-function-argument insertion). I'm not aware of any live bug of that sort with core datatypes, and it might be unreachable for extension types as well because of restrictions of CREATE CAST, but I'm not entirely convinced that it's unreachable. Hence, it seems worth back-patching the fix (although I only went back to v14, as the patch doesn't apply cleanly at all in v13). There are several places in the rewriter that are building null domain constants the same way as preptlist.c. While those are before the planner and hence don't have any reachable bug, they're still applying a length coercion that will be const-folded away later, uselessly wasting cycles. Hence, make a utility routine that all of these places can call to do it right. Making this code more careful about the typmod assigned to the generated NULL constant has visible but cosmetic effects on some of the plans shown in contrib/postgres_fdw's regression tests. Discussion: https://postgr.es/m/1865579.1738113656@sss.pgh.pa.us Backpatch-through: 14 --- .../postgres_fdw/expected/postgres_fdw.out | 24 +++++------ src/backend/optimizer/prep/preptlist.c | 31 ++++++-------- src/backend/parser/parse_coerce.c | 37 ++++++++++++++++ src/backend/rewrite/rewriteHandler.c | 42 +++++-------------- src/backend/rewrite/rewriteManip.c | 28 +++++++------ src/include/parser/parse_coerce.h | 3 ++ 6 files changed, 89 insertions(+), 76 deletions(-) diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index 94b590cfd3a..e295a1a8f01 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -4127,13 +4127,13 @@ EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st6; PREPARE st7 AS INSERT INTO ft1 (c1,c2,c3) VALUES (1001,101,'foo'); EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st7; - QUERY PLAN -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + QUERY PLAN +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Insert on public.ft1 Remote SQL: INSERT INTO "S 1"."T 1"("C 1", c2, c3, c4, c5, c6, c7, c8) VALUES ($1, $2, $3, $4, $5, $6, $7, $8) Batch Size: 1 -> Result - Output: NULL::integer, 1001, 101, 'foo'::text, NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying, 'ft1 '::character(10), NULL::user_enum + Output: NULL::integer, 1001, 101, 'foo'::text, NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying(10), 'ft1 '::character(10), NULL::user_enum (5 rows) ALTER TABLE "S 1"."T 1" RENAME TO "T 0"; @@ -4161,13 +4161,13 @@ EXECUTE st6; (9 rows) EXPLAIN (VERBOSE, COSTS OFF) EXECUTE st7; - QUERY PLAN -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + QUERY PLAN +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Insert on public.ft1 Remote SQL: INSERT INTO "S 1"."T 0"("C 1", c2, c3, c4, c5, c6, c7, c8) VALUES ($1, $2, $3, $4, $5, $6, $7, $8) Batch Size: 1 -> Result - Output: NULL::integer, 1001, 101, 'foo'::text, NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying, 'ft1 '::character(10), NULL::user_enum + Output: NULL::integer, 1001, 101, 'foo'::text, NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying(10), 'ft1 '::character(10), NULL::user_enum (5 rows) ALTER TABLE "S 1"."T 0" RENAME TO "T 1"; @@ -4491,13 +4491,13 @@ explain (verbose, costs off) select * from ft3 f, loct3 l -- =================================================================== EXPLAIN (verbose, costs off) INSERT INTO ft2 (c1,c2,c3) SELECT c1+1000,c2+100, c3 || c3 FROM ft2 LIMIT 20; - QUERY PLAN --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + QUERY PLAN +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Insert on public.ft2 Remote SQL: INSERT INTO "S 1"."T 1"("C 1", c2, c3, c4, c5, c6, c7, c8) VALUES ($1, $2, $3, $4, $5, $6, $7, $8) Batch Size: 1 -> Subquery Scan on "*SELECT*" - Output: "*SELECT*"."?column?", "*SELECT*"."?column?_1", NULL::integer, "*SELECT*"."?column?_2", NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying, 'ft2 '::character(10), NULL::user_enum + Output: "*SELECT*"."?column?", "*SELECT*"."?column?_1", NULL::integer, "*SELECT*"."?column?_2", NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying(10), 'ft2 '::character(10), NULL::user_enum -> Foreign Scan on public.ft2 ft2_1 Output: (ft2_1.c1 + 1000), (ft2_1.c2 + 100), (ft2_1.c3 || ft2_1.c3) Remote SQL: SELECT "C 1", c2, c3 FROM "S 1"."T 1" LIMIT 20::bigint @@ -5607,14 +5607,14 @@ SELECT c1,c2,c3,c4 FROM ft2 ORDER BY c1; EXPLAIN (verbose, costs off) INSERT INTO ft2 (c1,c2,c3) VALUES (1200,999,'foo') RETURNING tableoid::regclass; - QUERY PLAN -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + QUERY PLAN +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Insert on public.ft2 Output: (ft2.tableoid)::regclass Remote SQL: INSERT INTO "S 1"."T 1"("C 1", c2, c3, c4, c5, c6, c7, c8) VALUES ($1, $2, $3, $4, $5, $6, $7, $8) Batch Size: 1 -> Result - Output: 1200, 999, NULL::integer, 'foo'::text, NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying, 'ft2 '::character(10), NULL::user_enum + Output: 1200, 999, NULL::integer, 'foo'::text, NULL::timestamp with time zone, NULL::timestamp without time zone, NULL::character varying(10), 'ft2 '::character(10), NULL::user_enum (6 rows) INSERT INTO ft2 (c1,c2,c3) VALUES (1200,999,'foo') RETURNING tableoid::regclass; diff --git a/src/backend/optimizer/prep/preptlist.c b/src/backend/optimizer/prep/preptlist.c index e9434580d6d..e9151c9589a 100644 --- a/src/backend/optimizer/prep/preptlist.c +++ b/src/backend/optimizer/prep/preptlist.c @@ -46,7 +46,8 @@ #include "parser/parsetree.h" #include "utils/rel.h" -static List *expand_insert_targetlist(List *tlist, Relation rel); +static List *expand_insert_targetlist(PlannerInfo *root, List *tlist, + Relation rel); /* @@ -102,7 +103,7 @@ preprocess_targetlist(PlannerInfo *root) */ tlist = parse->targetList; if (command_type == CMD_INSERT) - tlist = expand_insert_targetlist(tlist, target_relation); + tlist = expand_insert_targetlist(root, tlist, target_relation); else if (command_type == CMD_UPDATE) root->update_colnos = extract_update_targetlist_colnos(tlist); @@ -292,7 +293,7 @@ extract_update_targetlist_colnos(List *tlist) * but now this code is only applied to INSERT targetlists. */ static List * -expand_insert_targetlist(List *tlist, Relation rel) +expand_insert_targetlist(PlannerInfo *root, List *tlist, Relation rel) { List *new_tlist = NIL; ListCell *tlist_item; @@ -346,26 +347,18 @@ expand_insert_targetlist(List *tlist, Relation rel) * confuse code comparing the finished plan to the target * relation, however. */ - Oid atttype = att_tup->atttypid; - Oid attcollation = att_tup->attcollation; Node *new_expr; if (!att_tup->attisdropped) { - new_expr = (Node *) makeConst(atttype, - -1, - attcollation, - att_tup->attlen, - (Datum) 0, - true, /* isnull */ - att_tup->attbyval); - new_expr = coerce_to_domain(new_expr, - InvalidOid, -1, - atttype, - COERCION_IMPLICIT, - COERCE_IMPLICIT_CAST, - -1, - false); + new_expr = coerce_null_to_domain(att_tup->atttypid, + att_tup->atttypmod, + att_tup->attcollation, + att_tup->attlen, + att_tup->attbyval); + /* Must run expression preprocessing on any non-const nodes */ + if (!IsA(new_expr, Const)) + new_expr = eval_const_expressions(root, new_expr); } else { diff --git a/src/backend/parser/parse_coerce.c b/src/backend/parser/parse_coerce.c index fc9224c5c0c..79ffdd2a9d1 100644 --- a/src/backend/parser/parse_coerce.c +++ b/src/backend/parser/parse_coerce.c @@ -1263,6 +1263,43 @@ coerce_to_specific_type(ParseState *pstate, Node *node, constructName); } +/* + * coerce_null_to_domain() + * Build a NULL constant, then wrap it in CoerceToDomain + * if the desired type is a domain type. This allows any + * NOT NULL domain constraint to be enforced at runtime. + */ +Node * +coerce_null_to_domain(Oid typid, int32 typmod, Oid collation, + int typlen, bool typbyval) +{ + Node *result; + Oid baseTypeId; + int32 baseTypeMod = typmod; + + /* + * The constant must appear to have the domain's base type/typmod, else + * coerce_to_domain() will apply a length coercion which is useless. + */ + baseTypeId = getBaseTypeAndTypmod(typid, &baseTypeMod); + result = (Node *) makeConst(baseTypeId, + baseTypeMod, + collation, + typlen, + (Datum) 0, + true, /* isnull */ + typbyval); + if (typid != baseTypeId) + result = coerce_to_domain(result, + baseTypeId, baseTypeMod, + typid, + COERCION_IMPLICIT, + COERCE_IMPLICIT_CAST, + -1, + false); + return result; +} + /* * parser_coercion_errposition - report coercion error location, if possible * diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c index 4243a58cf80..d069a9157a3 100644 --- a/src/backend/rewrite/rewriteHandler.c +++ b/src/backend/rewrite/rewriteHandler.c @@ -997,23 +997,11 @@ rewriteTargetListIU(List *targetList, if (commandType == CMD_INSERT) new_tle = NULL; else - { - new_expr = (Node *) makeConst(att_tup->atttypid, - -1, - att_tup->attcollation, - att_tup->attlen, - (Datum) 0, - true, /* isnull */ - att_tup->attbyval); - /* this is to catch a NOT NULL domain constraint */ - new_expr = coerce_to_domain(new_expr, - InvalidOid, -1, - att_tup->atttypid, - COERCION_IMPLICIT, - COERCE_IMPLICIT_CAST, - -1, - false); - } + new_expr = coerce_null_to_domain(att_tup->atttypid, + att_tup->atttypmod, + att_tup->attcollation, + att_tup->attlen, + att_tup->attbyval); } if (new_expr) @@ -1575,21 +1563,11 @@ rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti, continue; } - new_expr = (Node *) makeConst(att_tup->atttypid, - -1, - att_tup->attcollation, - att_tup->attlen, - (Datum) 0, - true, /* isnull */ - att_tup->attbyval); - /* this is to catch a NOT NULL domain constraint */ - new_expr = coerce_to_domain(new_expr, - InvalidOid, -1, - att_tup->atttypid, - COERCION_IMPLICIT, - COERCE_IMPLICIT_CAST, - -1, - false); + new_expr = coerce_null_to_domain(att_tup->atttypid, + att_tup->atttypmod, + att_tup->attcollation, + att_tup->attlen, + att_tup->attbyval); } newList = lappend(newList, new_expr); } diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c index 7f40d1dc806..8cf58291ec0 100644 --- a/src/backend/rewrite/rewriteManip.c +++ b/src/backend/rewrite/rewriteManip.c @@ -22,6 +22,7 @@ #include "parser/parse_relation.h" #include "parser/parsetree.h" #include "rewrite/rewriteManip.h" +#include "utils/lsyscache.h" typedef struct @@ -1466,20 +1467,21 @@ ReplaceVarsFromTargetList_callback(Var *var, return (Node *) var; case REPLACEVARS_SUBSTITUTE_NULL: + { + /* + * If Var is of domain type, we must add a CoerceToDomain + * node, in case there is a NOT NULL domain constraint. + */ + int16 vartyplen; + bool vartypbyval; - /* - * If Var is of domain type, we should add a CoerceToDomain - * node, in case there is a NOT NULL domain constraint. - */ - return coerce_to_domain((Node *) makeNullConst(var->vartype, - var->vartypmod, - var->varcollid), - InvalidOid, -1, - var->vartype, - COERCION_IMPLICIT, - COERCE_IMPLICIT_CAST, - -1, - false); + get_typlenbyval(var->vartype, &vartyplen, &vartypbyval); + return coerce_null_to_domain(var->vartype, + var->vartypmod, + var->varcollid, + vartyplen, + vartypbyval); + } } elog(ERROR, "could not find replacement targetlist entry for attno %d", var->varattno); diff --git a/src/include/parser/parse_coerce.h b/src/include/parser/parse_coerce.h index 96c230c3870..ed0c92b9e21 100644 --- a/src/include/parser/parse_coerce.h +++ b/src/include/parser/parse_coerce.h @@ -61,6 +61,9 @@ extern Node *coerce_to_specific_type_typmod(ParseState *pstate, Node *node, Oid targetTypeId, int32 targetTypmod, const char *constructName); +extern Node *coerce_null_to_domain(Oid typid, int32 typmod, Oid collation, + int typlen, bool typbyval); + extern int parser_coercion_errposition(ParseState *pstate, int coerce_location, Node *input_expr);