From dd8d5a6c037b6d761ef3af1b5c3440537215ee80 Mon Sep 17 00:00:00 2001 From: Laurenz Albe Date: Wed, 13 Nov 2024 15:07:03 +0100 Subject: [PATCH 16/22] allow read an value of session variable directly from expression executor The expression executor can be called directly (not inside query executor) when expression is evaluated as simple expression in plpgsql or when expression is an argument of CALL or EXECUTE statements. For these cases we need to allow direct access to content of session variables from executor. We can do it, because we know so the expression is not evaluated under query and cannot be evaluated inside parallel worker. This patch enables session variables for simple expression evaluation. This patch enables usage session variables in arguments of CALL stmt. --- src/backend/commands/prepare.c | 8 -- src/backend/executor/execExpr.c | 92 +++++++++++++++---- src/backend/executor/execExprInterp.c | 16 ++++ src/backend/jit/llvm/llvmjit_expr.c | 6 ++ src/backend/parser/analyze.c | 8 -- src/include/executor/execExpr.h | 12 ++- .../src/expected/plpgsql_session_variable.out | 3 +- src/pl/plpgsql/src/pl_exec.c | 3 +- .../regress/expected/session_variables.out | 41 ++++----- src/test/regress/sql/session_variables.sql | 12 +-- 10 files changed, 132 insertions(+), 69 deletions(-) diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c index 88c2135ac88..70f03099996 100644 --- a/src/backend/commands/prepare.c +++ b/src/backend/commands/prepare.c @@ -338,14 +338,6 @@ EvaluateParams(ParseState *pstate, PreparedStatement *pstmt, List *params, i++; } - /* - * The arguments of EXECUTE are evaluated by a direct expression - * executor call. This mode doesn't support session variables yet. - * It will be enabled later. - */ - if (pstate->p_hasSessionVariables) - elog(ERROR, "session variable cannot be used as an argument"); - /* Prepare the expressions for execution */ exprstates = ExecPrepareExprList(params, estate); diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c index c92a36b034b..bb50fe26d37 100644 --- a/src/backend/executor/execExpr.c +++ b/src/backend/executor/execExpr.c @@ -1009,25 +1009,79 @@ ExecInitExprRec(Expr *node, ExprState *state, es_num_session_variables = state->parent->state->es_num_session_variables; } - Assert(es_session_variables); - - /* parameter sanity checks */ - if (param->paramid >= es_num_session_variables) - elog(ERROR, "paramid of PARAM_VARIABLE param is out of range"); - - var = &es_session_variables[param->paramid]; - - if (var->typid != param->paramtype) - elog(ERROR, "type of buffered value is different than PARAM_VARIABLE type"); - - /* - * In this case, pass the value like a - * constant. - */ - scratch.opcode = EEOP_CONST; - scratch.d.constval.value = var->value; - scratch.d.constval.isnull = var->isnull; - ExprEvalPushStep(state, &scratch); + if (es_session_variables) + { + /* + * This path is used when expression is + * evaluated inside query evaluation. For + * ensuring of immutability of session variable + * inside query we use special buffer with copy + * of used session variables. This method helps + * with parallel execution too. + */ + + /* parameter sanity checks */ + if (param->paramid >= es_num_session_variables) + elog(ERROR, "paramid of PARAM_VARIABLE param is out of range"); + + var = &es_session_variables[param->paramid]; + + if (var->typid != param->paramtype) + elog(ERROR, "type of buffered value is different than PARAM_VARIABLE type"); + + /* + * In this case, pass the value like a + * constant. + */ + scratch.opcode = EEOP_CONST; + scratch.d.constval.value = var->value; + scratch.d.constval.isnull = var->isnull; + ExprEvalPushStep(state, &scratch); + } + else + { + Oid varid = param->paramvarid; + Oid vartype = param->paramtype; + + Assert(!IsParallelWorker()); + + /* + * In some cases (plpgsql's simple expression + * evaluation or evaluation of CALL arguments), + * the expression executor is called directly. + * We can allow direct access to session + * variables (copy only), because we know, so + * outside is not any query (and expression + * cannot be executed parallel). + * + * In this case we should to do aclcheck, + * because usual aclcheck from + * standard_ExecutorStart is not executed in + * this case. Fortunately it is just once per + * transaction. + * + * Don't do permission check, when variable is + * used like base node for assignment indirection. + */ + if (!param->parambasenode) + { + AclResult aclresult; + + aclresult = object_aclcheck( + VariableRelationId, varid, + GetUserId(), ACL_SELECT); + + if (aclresult != ACLCHECK_OK) + aclcheck_error(aclresult, + OBJECT_VARIABLE, + get_session_variable_name(varid)); + } + + scratch.opcode = EEOP_PARAM_VARIABLE; + scratch.d.vparam.varid = varid; + scratch.d.vparam.vartype = vartype; + ExprEvalPushStep(state, &scratch); + } } break; diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c index b2c00a0a1b1..c1287efb4b1 100644 --- a/src/backend/executor/execExprInterp.c +++ b/src/backend/executor/execExprInterp.c @@ -59,6 +59,7 @@ #include "access/heaptoast.h" #include "catalog/pg_type.h" #include "commands/sequence.h" +#include "commands/session_variable.h" #include "executor/execExpr.h" #include "executor/nodeSubplan.h" #include "funcapi.h" @@ -512,6 +513,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull) &&CASE_EEOP_PARAM_EXEC, &&CASE_EEOP_PARAM_EXTERN, &&CASE_EEOP_PARAM_CALLBACK, + &&CASE_EEOP_PARAM_VARIABLE, &&CASE_EEOP_PARAM_SET, &&CASE_EEOP_CASE_TESTVAL, &&CASE_EEOP_MAKE_READONLY, @@ -1161,6 +1163,20 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull) EEO_NEXT(); } + EEO_CASE(EEOP_PARAM_VARIABLE) + { + /* + * Direct access to session variable (without buffering). Because + * returned value can be used (without an assignement) after the + * referenced session variables is updated, we have to use an copy + * of stored value every time. + */ + *op->resvalue = GetSessionVariableWithTypeCheck(op->d.vparam.varid, + op->resnull, + op->d.vparam.vartype); + EEO_NEXT(); + } + EEO_CASE(EEOP_PARAM_SET) { /* out of line, unlikely to matter performance-wise */ diff --git a/src/backend/jit/llvm/llvmjit_expr.c b/src/backend/jit/llvm/llvmjit_expr.c index 6c4915e3731..0b73c5f3545 100644 --- a/src/backend/jit/llvm/llvmjit_expr.c +++ b/src/backend/jit/llvm/llvmjit_expr.c @@ -1136,6 +1136,12 @@ llvm_compile_expr(ExprState *state) break; } + case EEOP_PARAM_VARIABLE: + build_EvalXFunc(b, mod, "ExecEvalParamVariable", + v_state, op, v_econtext); + LLVMBuildBr(b, opblocks[opno + 1]); + break; + case EEOP_PARAM_SET: build_EvalXFunc(b, mod, "ExecEvalParamSet", v_state, op, v_econtext); diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c index 47df024cdf9..b8df16e4f09 100644 --- a/src/backend/parser/analyze.c +++ b/src/backend/parser/analyze.c @@ -3469,14 +3469,6 @@ transformCallStmt(ParseState *pstate, CallStmt *stmt) true, stmt->funccall->location); - /* - * The arguments of CALL statement are evaluated by a direct expression - * executor call. This path is unsupported yet, so block it. It will be - * enabled later. - */ - if (pstate->p_hasSessionVariables) - elog(ERROR, "session variable cannot be used as an argument"); - assign_expr_collations(pstate, node); fexpr = castNode(FuncExpr, node); diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h index 8019e5490e9..431457ee7bc 100644 --- a/src/include/executor/execExpr.h +++ b/src/include/executor/execExpr.h @@ -156,10 +156,11 @@ typedef enum ExprEvalOp EEOP_BOOLTEST_IS_FALSE, EEOP_BOOLTEST_IS_NOT_FALSE, - /* evaluate PARAM_EXEC/EXTERN parameters */ + /* evaluate PARAM_EXEC/EXTERN/VARIABLE parameters */ EEOP_PARAM_EXEC, EEOP_PARAM_EXTERN, EEOP_PARAM_CALLBACK, + EEOP_PARAM_VARIABLE, /* set PARAM_EXEC value */ EEOP_PARAM_SET, @@ -410,6 +411,13 @@ typedef struct ExprEvalStep Oid paramtype; /* OID of parameter's datatype */ } cparam; + /* for EEOP_PARAM_VARIABLE */ + struct + { + Oid varid; /* OID of assigned variable */ + Oid vartype; /* OID of parameter's datatype */ + } vparam; + /* for EEOP_CASE_TESTVAL/DOMAIN_TESTVAL */ struct { @@ -832,6 +840,8 @@ extern void ExecEvalParamSet(ExprState *state, ExprEvalStep *op, ExprContext *econtext); extern void ExecEvalParamExtern(ExprState *state, ExprEvalStep *op, ExprContext *econtext); +extern void ExecEvalParamVariable(ExprState *state, ExprEvalStep *op, + ExprContext *econtext); extern void ExecEvalCoerceViaIOSafe(ExprState *state, ExprEvalStep *op); extern void ExecEvalSQLValueFunction(ExprState *state, ExprEvalStep *op); extern void ExecEvalCurrentOfExpr(ExprState *state, ExprEvalStep *op); diff --git a/src/pl/plpgsql/src/expected/plpgsql_session_variable.out b/src/pl/plpgsql/src/expected/plpgsql_session_variable.out index a6523f7afe2..ecac64fcfb4 100644 --- a/src/pl/plpgsql/src/expected/plpgsql_session_variable.out +++ b/src/pl/plpgsql/src/expected/plpgsql_session_variable.out @@ -211,8 +211,7 @@ SET ROLE TO regress_var_exec_role; -- should fail SELECT var_read_func(); ERROR: permission denied for session variable plpgsql_sv_var1 -CONTEXT: PL/pgSQL expression "plpgsql_sv_var1" -PL/pgSQL function var_read_func() line 3 at RAISE +CONTEXT: PL/pgSQL function var_read_func() line 3 at RAISE SET ROLE TO DEFAULT; SET ROLE TO regress_var_owner_role; GRANT SELECT ON VARIABLE plpgsql_sv_var1 TO regress_var_reader_role; diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c index 3f901cd8fcd..e5b0da04e3c 100644 --- a/src/pl/plpgsql/src/pl_exec.c +++ b/src/pl/plpgsql/src/pl_exec.c @@ -8099,8 +8099,7 @@ exec_is_simple_query(PLpgSQL_expr *expr) query->sortClause || query->limitOffset || query->limitCount || - query->setOperations || - query->hasSessionVariables) + query->setOperations) return false; /* diff --git a/src/test/regress/expected/session_variables.out b/src/test/regress/expected/session_variables.out index dd667d50c81..1f4e2b5d8c5 100644 --- a/src/test/regress/expected/session_variables.out +++ b/src/test/regress/expected/session_variables.out @@ -459,8 +459,7 @@ ERROR: permission denied for session variable var1 CONTEXT: SQL function "sqlfx" statement 1 SELECT plpgsqlfx(20); ERROR: permission denied for session variable var1 -CONTEXT: PL/pgSQL expression "$1 + var1" -PL/pgSQL function plpgsqlfx(integer) line 1 at RETURN +CONTEXT: PL/pgSQL function plpgsqlfx(integer) line 1 at RETURN -- should be ok SELECT sqlfx_sd(20); sqlfx_sd @@ -662,27 +661,28 @@ $$; NOTICE: result array: {1,2,3,4,5,6,7,8,9,10} DROP VARIABLE var1; DROP VARIABLE var2; --- CALL statement is not supported yet --- requires direct access to session variable from expression executor +-- CALL statement is supported CREATE VARIABLE v int; +LET v = 1; CREATE PROCEDURE p(arg int) AS $$ BEGIN RAISE NOTICE '%', arg; END $$ LANGUAGE plpgsql; --- should not crash (but is not supported yet) +-- should to work CALL p(v); -ERROR: session variable cannot be used as an argument +NOTICE: 1 DO $$ BEGIN CALL p(v); END $$; -ERROR: session variable cannot be used as an argument -CONTEXT: SQL statement "CALL p(v)" -PL/pgSQL function inline_code_block line 1 at CALL +NOTICE: 1 DROP PROCEDURE p(int); DROP VARIABLE v; --- EXECUTE statement is not supported yet --- requires direct access to session variable from expression executor +-- EXECUTE statement CREATE VARIABLE v int; LET v = 20; PREPARE ptest(int) AS SELECT $1; --- should fail +-- should be ok EXECUTE ptest(v); -ERROR: session variable cannot be used as an argument + ?column? +---------- + 20 +(1 row) + DEALLOCATE ptest; DROP VARIABLE v; -- test search path @@ -1001,12 +1001,10 @@ LET var1.a = var1.a + 10; ERROR: permission denied for session variable var1 DO $$ BEGIN RAISE NOTICE '%', var1; END $$; ERROR: permission denied for session variable var1 -CONTEXT: PL/pgSQL expression "var1" -PL/pgSQL function inline_code_block line 1 at RAISE +CONTEXT: PL/pgSQL function inline_code_block line 1 at RAISE DO $$ BEGIN RAISE NOTICE '%', var1.a; END $$; ERROR: permission denied for session variable var1 -CONTEXT: PL/pgSQL expression "var1.a" -PL/pgSQL function inline_code_block line 1 at RAISE +CONTEXT: PL/pgSQL function inline_code_block line 1 at RAISE DO $$ BEGIN LET var1.a = var1.a + 10; END $$; ERROR: permission denied for session variable var1 CONTEXT: SQL statement "LET var1.a = var1.a + 10" @@ -1045,12 +1043,10 @@ LET var1.a = var1.a + 10; ERROR: permission denied for session variable var1 DO $$ BEGIN RAISE NOTICE '%', var1; END $$; ERROR: permission denied for session variable var1 -CONTEXT: PL/pgSQL expression "var1" -PL/pgSQL function inline_code_block line 1 at RAISE +CONTEXT: PL/pgSQL function inline_code_block line 1 at RAISE DO $$ BEGIN RAISE NOTICE '%', var1.a; END $$; ERROR: permission denied for session variable var1 -CONTEXT: PL/pgSQL expression "var1.a" -PL/pgSQL function inline_code_block line 1 at RAISE +CONTEXT: PL/pgSQL function inline_code_block line 1 at RAISE DO $$ BEGIN LET var1.a = var1.a + 10; END $$; ERROR: permission denied for session variable var1 CONTEXT: SQL statement "LET var1.a = var1.a + 10" @@ -1954,8 +1950,7 @@ $$; ERROR: session variable "public.var1" is not used inside variable fence DETAIL: There is a risk of unwanted usage of session variable. HINT: Use variable fence "VARIABLE(varname) for access to variable". -CONTEXT: PL/pgSQL expression "var1" -PL/pgSQL function inline_code_block line 4 at RAISE +CONTEXT: PL/pgSQL function inline_code_block line 4 at RAISE -- should be ok SELECT VARIABLE(var1), VARIABLE(var1); var1 | var1 diff --git a/src/test/regress/sql/session_variables.sql b/src/test/regress/sql/session_variables.sql index a1d1abaa3dc..207013fbae0 100644 --- a/src/test/regress/sql/session_variables.sql +++ b/src/test/regress/sql/session_variables.sql @@ -438,13 +438,14 @@ $$; DROP VARIABLE var1; DROP VARIABLE var2; --- CALL statement is not supported yet --- requires direct access to session variable from expression executor +-- CALL statement is supported CREATE VARIABLE v int; +LET v = 1; + CREATE PROCEDURE p(arg int) AS $$ BEGIN RAISE NOTICE '%', arg; END $$ LANGUAGE plpgsql; --- should not crash (but is not supported yet) +-- should to work CALL p(v); DO $$ BEGIN CALL p(v); END $$; @@ -452,13 +453,12 @@ DO $$ BEGIN CALL p(v); END $$; DROP PROCEDURE p(int); DROP VARIABLE v; --- EXECUTE statement is not supported yet --- requires direct access to session variable from expression executor +-- EXECUTE statement CREATE VARIABLE v int; LET v = 20; PREPARE ptest(int) AS SELECT $1; --- should fail +-- should be ok EXECUTE ptest(v); DEALLOCATE ptest; -- 2.47.1