From a70720a7df82a3afb3f46f4a7548c030115b9a6f Mon Sep 17 00:00:00 2001 From: "okbob@github.com" Date: Sat, 20 Jan 2024 08:56:17 +0100 Subject: [PATCH 18/22] plpgsql implementation for LET statement PLpgSQL allows to call expression executor directly (for simple expression). This possibility strongly reduces overhead related to execution. Reimplementation of LET statement (inside PLpgSQL) allows to use this possibility, and strongly increase performance: CREATE VARIABLE svar int; DO $$ BEGIN FOR i IN 1..10000 LOOP LET svar = i; END LOOP; END; $$; From 120ms to 8ms (with assertions) (this is best case, but without it, the LET statement can be bottle neck). An alternative can be reimplementation of LET statement inside expression executor, and then SQL LET command can be executed in simple expression execution, but this increase an complexity of executor, but still the benefits is only inside plpgsql, so it is better to this optimization inside plpgsql. --- src/backend/commands/session_variable.c | 16 ++++++ src/backend/executor/spi.c | 3 + src/backend/parser/analyze.c | 12 ++++ src/backend/parser/gram.y | 8 +++ src/backend/parser/parser.c | 1 + src/include/commands/session_variable.h | 1 + src/include/nodes/parsenodes.h | 2 + src/include/parser/parser.h | 4 ++ src/pl/plpgsql/src/pl_exec.c | 56 +++++++++++++++++++ src/pl/plpgsql/src/pl_funcs.c | 24 ++++++++ src/pl/plpgsql/src/pl_gram.y | 28 +++++++++- src/pl/plpgsql/src/pl_reserved_kwlist.h | 1 + src/pl/plpgsql/src/pl_unreserved_kwlist.h | 1 + src/pl/plpgsql/src/plpgsql.h | 12 ++++ .../regress/expected/session_variables.out | 6 +- src/tools/pgindent/typedefs.list | 1 + 16 files changed, 171 insertions(+), 5 deletions(-) diff --git a/src/backend/commands/session_variable.c b/src/backend/commands/session_variable.c index f61900a9d4d..0cf23eb4810 100644 --- a/src/backend/commands/session_variable.c +++ b/src/backend/commands/session_variable.c @@ -956,6 +956,22 @@ SetSessionVariable(Oid varid, Datum value, bool isNull) set_session_variable(svar, value, isNull); } +/* + * Wrapper around SetSessionVariable with permission checks. + */ +void +SetSessionVariableWithSecurityCheck(Oid varid, Datum value, bool isNull) +{ + AclResult aclresult; + + /* is the caller allowed to update the session variable? */ + aclresult = object_aclcheck(VariableRelationId, varid, GetUserId(), ACL_UPDATE); + if (aclresult != ACLCHECK_OK) + aclcheck_error(aclresult, OBJECT_VARIABLE, get_session_variable_name(varid)); + + SetSessionVariable(varid, value, isNull); +} + /* * Returns a copy of the value stored in a variable. */ diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c index 4ce6bc5f298..e52d8cc13bc 100644 --- a/src/backend/executor/spi.c +++ b/src/backend/executor/spi.c @@ -2999,6 +2999,9 @@ _SPI_error_callback(void *arg) case RAW_PARSE_PLPGSQL_ASSIGN3: errcontext("PL/pgSQL assignment \"%s\"", query); break; + case RAW_PARSE_PLPGSQL_LET: + errcontext("LET statement \"%s\"", query); + break; default: errcontext("SQL statement \"%s\"", query); break; diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c index b8df16e4f09..0f91ec89c74 100644 --- a/src/backend/parser/analyze.c +++ b/src/backend/parser/analyze.c @@ -2013,6 +2013,18 @@ transformLetStmt(ParseState *pstate, LetStmt *stmt) stmt->query = (Node *) query; + /* + * Inside PL/pgSQL we don't want to execute LET statement as utility + * command, because it disallow to execute expression as simple + * expression. So for PL/pgSQL we have extra path, and we return SELECT. + * Then it can be executed by exec_eval_expr. Result is dirrectly assigned + * to target session variable inside PL/pgSQL LET statement handler. This + * is extra code, extra path, but possibility to get faster execution is + * too attractive. + */ + if (stmt->plpgsql_mode) + return query; + /* represent the command as a utility Query */ result = makeNode(Query); result->commandType = CMD_UTILITY; diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y index a59f6850b75..bf7ca3f51c6 100644 --- a/src/backend/parser/gram.y +++ b/src/backend/parser/gram.y @@ -816,6 +816,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query); %token MODE_PLPGSQL_ASSIGN1 %token MODE_PLPGSQL_ASSIGN2 %token MODE_PLPGSQL_ASSIGN3 +%token MODE_PLPGSQL_LET /* Precedence: lowest to highest */ @@ -947,6 +948,13 @@ parse_toplevel: pg_yyget_extra(yyscanner)->parsetree = list_make1(makeRawStmt((Node *) n, @2)); } + | MODE_PLPGSQL_LET LetStmt + { + LetStmt *n = (LetStmt *) $2; + n->plpgsql_mode = true; + pg_yyget_extra(yyscanner)->parsetree = + list_make1(makeRawStmt((Node *) n, 0)); + } ; /* diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c index 33a040506b4..887212aefde 100644 --- a/src/backend/parser/parser.c +++ b/src/backend/parser/parser.c @@ -62,6 +62,7 @@ raw_parser(const char *str, RawParseMode mode) [RAW_PARSE_PLPGSQL_ASSIGN1] = MODE_PLPGSQL_ASSIGN1, [RAW_PARSE_PLPGSQL_ASSIGN2] = MODE_PLPGSQL_ASSIGN2, [RAW_PARSE_PLPGSQL_ASSIGN3] = MODE_PLPGSQL_ASSIGN3, + [RAW_PARSE_PLPGSQL_LET] = MODE_PLPGSQL_LET, }; yyextra.have_lookahead = true; diff --git a/src/include/commands/session_variable.h b/src/include/commands/session_variable.h index 23841ab373b..86112b43b46 100644 --- a/src/include/commands/session_variable.h +++ b/src/include/commands/session_variable.h @@ -28,6 +28,7 @@ extern void AtEOSubXact_SessionVariables(bool isCommit, SubTransactionId mySubid SubTransactionId parentSubid); extern void SetSessionVariable(Oid varid, Datum value, bool isNull); +extern void SetSessionVariableWithSecurityCheck(Oid varid, Datum value, bool isNull); extern Datum GetSessionVariable(Oid varid, bool *isNull, Oid *typid); extern Datum GetSessionVariableWithTypeCheck(Oid varid, bool *isNull, Oid expected_typid); diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h index 1a7f443ce75..990cebbf08b 100644 --- a/src/include/nodes/parsenodes.h +++ b/src/include/nodes/parsenodes.h @@ -2124,6 +2124,8 @@ typedef struct LetStmt NodeTag type; List *target; /* target variable */ Node *query; /* source expression */ + bool plpgsql_mode; /* true, when command will be executed + * (parsed) by plpgsql runtime */ ParseLoc location; } LetStmt; diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h index 350196cd641..c8d5e8dbf92 100644 --- a/src/include/parser/parser.h +++ b/src/include/parser/parser.h @@ -33,6 +33,9 @@ * RAW_PARSE_PLPGSQL_ASSIGNn: parse a PL/pgSQL assignment statement, * and return a one-element List containing a RawStmt node. "n" * gives the number of dotted names comprising the target ColumnRef. + * + * RAW_PARSE_PLPGSQL_LET: parse a LET statement, and return a + * one-element List containing a RawStmt node. */ typedef enum { @@ -42,6 +45,7 @@ typedef enum RAW_PARSE_PLPGSQL_ASSIGN1, RAW_PARSE_PLPGSQL_ASSIGN2, RAW_PARSE_PLPGSQL_ASSIGN3, + RAW_PARSE_PLPGSQL_LET, } RawParseMode; /* Values for the backslash_quote GUC */ diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c index e5b0da04e3c..2b92fb5eea4 100644 --- a/src/pl/plpgsql/src/pl_exec.c +++ b/src/pl/plpgsql/src/pl_exec.c @@ -22,6 +22,7 @@ #include "access/tupconvert.h" #include "catalog/pg_proc.h" #include "catalog/pg_type.h" +#include "commands/session_variable.h" #include "executor/execExpr.h" #include "executor/spi.h" #include "executor/tstoreReceiver.h" @@ -323,6 +324,8 @@ static int exec_stmt_commit(PLpgSQL_execstate *estate, PLpgSQL_stmt_commit *stmt); static int exec_stmt_rollback(PLpgSQL_execstate *estate, PLpgSQL_stmt_rollback *stmt); +static int exec_stmt_let(PLpgSQL_execstate *estate, + PLpgSQL_stmt_let *let); static void plpgsql_estate_setup(PLpgSQL_execstate *estate, PLpgSQL_function *func, @@ -2116,6 +2119,10 @@ exec_stmts(PLpgSQL_execstate *estate, List *stmts) rc = exec_stmt_rollback(estate, (PLpgSQL_stmt_rollback *) stmt); break; + case PLPGSQL_STMT_LET: + rc = exec_stmt_let(estate, (PLpgSQL_stmt_let *) stmt); + break; + default: /* point err_stmt to parent, since this one seems corrupt */ estate->err_stmt = save_estmt; @@ -4999,6 +5006,55 @@ exec_stmt_rollback(PLpgSQL_execstate *estate, PLpgSQL_stmt_rollback *stmt) return PLPGSQL_RC_OK; } +/* ---------- + * exec_stmt_let Evaluate an expression and + * put the result into a session variable. + * ---------- + */ +static int +exec_stmt_let(PLpgSQL_execstate *estate, PLpgSQL_stmt_let *stmt) +{ + bool isNull; + Oid valtype; + int32 valtypmod; + Datum value; + Oid varid; + + List *plansources; + CachedPlanSource *plansource; + + value = exec_eval_expr(estate, + stmt->expr, + &isNull, + &valtype, + &valtypmod); + + /* + * Oid of target session variable is stored in Query structure. It is + * safer to read this value directly from the plan than to hold this value + * in the plpgsql context, because it's not necessary to handle + * invalidation of the cached value. Next operations are read only without + * any allocations, so we can expect that retrieving varid from Query + * should be fast. + */ + plansources = SPI_plan_get_plan_sources(stmt->expr->plan); + if (list_length(plansources) != 1) + elog(ERROR, "unexpected length of plansources of query for LET statement"); + + plansource = (CachedPlanSource *) linitial(plansources); + if (list_length(plansource->query_list) != 1) + elog(ERROR, "unexpected length of plansource of query for LET statement"); + + varid = linitial_node(Query, plansource->query_list)->resultVariable; + if (!OidIsValid(varid)) + elog(ERROR, "oid of target session variable is not valid"); + + SetSessionVariableWithSecurityCheck(varid, value, isNull); + exec_eval_cleanup(estate); + + return PLPGSQL_RC_OK; +} + /* ---------- * exec_assign_expr Put an expression's result into a variable. * ---------- diff --git a/src/pl/plpgsql/src/pl_funcs.c b/src/pl/plpgsql/src/pl_funcs.c index 8c827fe5cc5..f748df048c4 100644 --- a/src/pl/plpgsql/src/pl_funcs.c +++ b/src/pl/plpgsql/src/pl_funcs.c @@ -288,6 +288,8 @@ plpgsql_stmt_typename(PLpgSQL_stmt *stmt) return "COMMIT"; case PLPGSQL_STMT_ROLLBACK: return "ROLLBACK"; + case PLPGSQL_STMT_LET: + return "LET"; } return "unknown"; @@ -370,6 +372,7 @@ static void free_perform(PLpgSQL_stmt_perform *stmt); static void free_call(PLpgSQL_stmt_call *stmt); static void free_commit(PLpgSQL_stmt_commit *stmt); static void free_rollback(PLpgSQL_stmt_rollback *stmt); +static void free_let(PLpgSQL_stmt_let *stmt); static void free_expr(PLpgSQL_expr *expr); @@ -459,6 +462,9 @@ free_stmt(PLpgSQL_stmt *stmt) case PLPGSQL_STMT_ROLLBACK: free_rollback((PLpgSQL_stmt_rollback *) stmt); break; + case PLPGSQL_STMT_LET: + free_let((PLpgSQL_stmt_let *) stmt); + break; default: elog(ERROR, "unrecognized cmd_type: %d", stmt->cmd_type); break; @@ -713,6 +719,12 @@ free_getdiag(PLpgSQL_stmt_getdiag *stmt) { } +static void +free_let(PLpgSQL_stmt_let *stmt) +{ + free_expr(stmt->expr); +} + static void free_expr(PLpgSQL_expr *expr) { @@ -815,6 +827,7 @@ static void dump_perform(PLpgSQL_stmt_perform *stmt); static void dump_call(PLpgSQL_stmt_call *stmt); static void dump_commit(PLpgSQL_stmt_commit *stmt); static void dump_rollback(PLpgSQL_stmt_rollback *stmt); +static void dump_let(PLpgSQL_stmt_let *stmt); static void dump_expr(PLpgSQL_expr *expr); @@ -914,6 +927,9 @@ dump_stmt(PLpgSQL_stmt *stmt) case PLPGSQL_STMT_ROLLBACK: dump_rollback((PLpgSQL_stmt_rollback *) stmt); break; + case PLPGSQL_STMT_LET: + dump_let((PLpgSQL_stmt_let *) stmt); + break; default: elog(ERROR, "unrecognized cmd_type: %d", stmt->cmd_type); break; @@ -1590,6 +1606,14 @@ dump_getdiag(PLpgSQL_stmt_getdiag *stmt) printf("\n"); } +static void +dump_let(PLpgSQL_stmt_let *stmt) +{ + dump_ind(); + dump_expr(stmt->expr); + printf("\n"); +} + static void dump_expr(PLpgSQL_expr *expr) { diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y index 9783063258f..f09cc597def 100644 --- a/src/pl/plpgsql/src/pl_gram.y +++ b/src/pl/plpgsql/src/pl_gram.y @@ -200,7 +200,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt); %type stmt_return stmt_raise stmt_assert stmt_execsql %type stmt_dynexecute stmt_for stmt_perform stmt_call stmt_getdiag %type stmt_open stmt_fetch stmt_move stmt_close stmt_null -%type stmt_commit stmt_rollback +%type stmt_commit stmt_rollback stmt_let %type stmt_case stmt_foreach_a %type proc_exceptions @@ -307,6 +307,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt); %token K_INTO %token K_IS %token K_LAST +%token K_LET %token K_LOG %token K_LOOP %token K_MERGE @@ -876,6 +877,8 @@ proc_stmt : pl_block ';' { $$ = $1; } | stmt_rollback { $$ = $1; } + | stmt_let + { $$ = $1; } ; stmt_perform : K_PERFORM @@ -992,6 +995,29 @@ stmt_assign : T_DATUM } ; +stmt_let : K_LET + { + PLpgSQL_stmt_let *new; + RawParseMode pmode; + + pmode = RAW_PARSE_PLPGSQL_LET; + + new = palloc0(sizeof(PLpgSQL_stmt_let)); + new->cmd_type = PLPGSQL_STMT_LET; + new->lineno = plpgsql_location_to_lineno(@1); + new->stmtid = ++plpgsql_curr_compile->nstatements; + + /* push back the head name to include it in the stmt */ + plpgsql_push_back_token(K_LET); + new->expr = read_sql_construct(';', 0, 0, ";", + pmode, + false, true, + NULL, NULL); + + $$ = (PLpgSQL_stmt *)new; + } + ; + stmt_getdiag : K_GET getdiag_area_opt K_DIAGNOSTICS getdiag_list ';' { PLpgSQL_stmt_getdiag *new; diff --git a/src/pl/plpgsql/src/pl_reserved_kwlist.h b/src/pl/plpgsql/src/pl_reserved_kwlist.h index ce7b0c9d331..e266bd1cc46 100644 --- a/src/pl/plpgsql/src/pl_reserved_kwlist.h +++ b/src/pl/plpgsql/src/pl_reserved_kwlist.h @@ -40,6 +40,7 @@ PG_KEYWORD("from", K_FROM) PG_KEYWORD("if", K_IF) PG_KEYWORD("in", K_IN) PG_KEYWORD("into", K_INTO) +PG_KEYWORD("let", K_LET) PG_KEYWORD("loop", K_LOOP) PG_KEYWORD("not", K_NOT) PG_KEYWORD("null", K_NULL) diff --git a/src/pl/plpgsql/src/pl_unreserved_kwlist.h b/src/pl/plpgsql/src/pl_unreserved_kwlist.h index 98f99ec470c..ed14fd86c31 100644 --- a/src/pl/plpgsql/src/pl_unreserved_kwlist.h +++ b/src/pl/plpgsql/src/pl_unreserved_kwlist.h @@ -69,6 +69,7 @@ PG_KEYWORD("info", K_INFO) PG_KEYWORD("insert", K_INSERT) PG_KEYWORD("is", K_IS) PG_KEYWORD("last", K_LAST) +PG_KEYWORD("let", K_LET) PG_KEYWORD("log", K_LOG) PG_KEYWORD("merge", K_MERGE) PG_KEYWORD("message", K_MESSAGE) diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h index d00b9ce0da2..601c5e59229 100644 --- a/src/pl/plpgsql/src/plpgsql.h +++ b/src/pl/plpgsql/src/plpgsql.h @@ -128,6 +128,7 @@ typedef enum PLpgSQL_stmt_type PLPGSQL_STMT_CALL, PLPGSQL_STMT_COMMIT, PLPGSQL_STMT_ROLLBACK, + PLPGSQL_STMT_LET, } PLpgSQL_stmt_type; /* @@ -520,6 +521,17 @@ typedef struct PLpgSQL_stmt_assign PLpgSQL_expr *expr; } PLpgSQL_stmt_assign; +/* + * Let statement + */ +typedef struct PLpgSQL_stmt_let +{ + PLpgSQL_stmt_type cmd_type; + int lineno; + unsigned int stmtid; + PLpgSQL_expr *expr; +} PLpgSQL_stmt_let; + /* * PERFORM statement */ diff --git a/src/test/regress/expected/session_variables.out b/src/test/regress/expected/session_variables.out index a65311e9352..9dee21986fa 100644 --- a/src/test/regress/expected/session_variables.out +++ b/src/test/regress/expected/session_variables.out @@ -1125,8 +1125,7 @@ ERROR: permission denied for session variable var1 CONTEXT: PL/pgSQL function inline_code_block line 1 at RAISE DO $$ BEGIN LET var1.a = var1.a + 10; END $$; ERROR: permission denied for session variable var1 -CONTEXT: SQL statement "LET var1.a = var1.a + 10" -PL/pgSQL function inline_code_block line 1 at SQL statement +CONTEXT: PL/pgSQL function inline_code_block line 1 at LET SET ROLE TO DEFAULT; GRANT SELECT ON VARIABLE var1 TO regress_var_test_role; SET ROLE TO regress_var_test_role; @@ -1167,8 +1166,7 @@ ERROR: permission denied for session variable var1 CONTEXT: PL/pgSQL function inline_code_block line 1 at RAISE DO $$ BEGIN LET var1.a = var1.a + 10; END $$; ERROR: permission denied for session variable var1 -CONTEXT: SQL statement "LET var1.a = var1.a + 10" -PL/pgSQL function inline_code_block line 1 at SQL statement +CONTEXT: PL/pgSQL function inline_code_block line 1 at LET SET ROLE TO DEFAULT; DROP VARIABLE var1; DROP ROLE regress_var_test_role; diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 5c875ae6846..7ae5b88feb1 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -1893,6 +1893,7 @@ PLpgSQL_stmt_forq PLpgSQL_stmt_fors PLpgSQL_stmt_getdiag PLpgSQL_stmt_if +PLpgSQL_stmt_let PLpgSQL_stmt_loop PLpgSQL_stmt_open PLpgSQL_stmt_perform -- 2.47.1