From 2e2ea737629334cfee24e47f44dd5614ff9802d9 Mon Sep 17 00:00:00 2001 From: Alexander Pyhalov Date: Thu, 15 Jan 2026 09:20:51 +0300 Subject: [PATCH 3/3] Introduce memory limited cursors and use them in postgres_fdw Parameter "cursor_fetch_limit" limits the number of records, which is retrieved by FETCH from memory limited cursors statement, based on batch size. FETCH ALL is not limited. When cursor_fetch_limit >= 0 and records count is passed to ExecutorRun(), we can't longer rely on fact that when executor returned less records than expected, there's no more records to fetch, so we introduce additional EState field which after ExecutorRun() call says if there are more records. As we explicitly mark which cursors can be subject to memory limits, we avoid affecting some uncontrolled code. --- contrib/postgres_fdw/connection.c | 13 +++ contrib/postgres_fdw/postgres_fdw.c | 25 ++++- src/backend/executor/execMain.c | 37 +++++- src/backend/executor/execUtils.c | 1 + src/backend/parser/gram.y | 9 +- src/backend/tcop/pquery.c | 56 ++++++++-- src/backend/utils/misc/guc_parameters.dat | 9 ++ src/backend/utils/misc/guc_tables.c | 1 + src/backend/utils/misc/postgresql.conf.sample | 1 + src/include/executor/executor.h | 4 +- src/include/nodes/execnodes.h | 1 + src/include/nodes/parsenodes.h | 1 + src/include/parser/kwlist.h | 2 + src/test/regress/expected/portals.out | 105 ++++++++++++++++++ src/test/regress/sql/portals.sql | 28 +++++ 15 files changed, 275 insertions(+), 18 deletions(-) diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c index 487a1a23170..d6c6c26b393 100644 --- a/contrib/postgres_fdw/connection.c +++ b/contrib/postgres_fdw/connection.c @@ -802,6 +802,19 @@ configure_remote_session(PGconn *conn) do_sql_command(conn, "SET extra_float_digits = 3"); else do_sql_command(conn, "SET extra_float_digits = 2"); + /* + * Limit fetch size with work_mem to avoid uncontrolled memory + * consumption. + */ + if (remoteversion >= 190000) + { + char sql[64]; + int fetch_limit; + + fetch_limit = (work_mem * 1024 > MaxAllocSize) ? MaxAllocSize : work_mem * 1024; + snprintf(sql, sizeof(sql), "SET cursor_fetch_limit = %d", fetch_limit); + do_sql_command(conn, sql); + } } /* diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 3572689e33b..25d708fe4f5 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -3731,6 +3731,8 @@ create_cursor(ForeignScanState *node) PGconn *conn = fsstate->conn; StringInfoData buf; PGresult *res; + const char *memory_limited = ""; + int remoteversion; /* First, process a pending asynchronous request, if any. */ if (fsstate->conn_state->pendingAreq) @@ -3757,8 +3759,13 @@ create_cursor(ForeignScanState *node) /* Construct the DECLARE CURSOR command */ initStringInfo(&buf); - appendStringInfo(&buf, "DECLARE c%u CURSOR FOR\n%s", - fsstate->cursor_number, fsstate->query); + + remoteversion = PQserverVersion(conn); + if (remoteversion >= 190000) + memory_limited = "MEMORY LIMITED "; + + appendStringInfo(&buf, "DECLARE c%u %sCURSOR FOR\n%s", + fsstate->cursor_number, memory_limited, fsstate->query); /* * Notice that we pass NULL for paramTypes, thus forcing the remote server @@ -3865,8 +3872,11 @@ fetch_more_data(ForeignScanState *node) if (fsstate->fetch_ct_2 < 2) fsstate->fetch_ct_2++; - /* Must be EOF if we didn't get as many tuples as we asked for. */ - fsstate->eof_reached = (numrows < fsstate->fetch_size); + /* + * Must be EOF if we got 0 rows. We can get less rows than we asked for + * even if there's more data if batch of "fetch_size" exceeds work_mem. + */ + fsstate->eof_reached = (numrows == 0); PQclear(res); @@ -5025,6 +5035,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel, char fetch_sql[64]; int fetch_size; ListCell *lc; + const char *memory_limited = ""; /* Initialize workspace state */ astate.rel = relation; @@ -5196,7 +5207,11 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel, */ cursor_number = GetCursorNumber(conn); initStringInfo(&sql); - appendStringInfo(&sql, "DECLARE c%u CURSOR FOR ", cursor_number); + + if (server_version_num >= 190000) + memory_limited = "MEMORY LIMITED "; + + appendStringInfo(&sql, "DECLARE c%u %sCURSOR FOR ", cursor_number, memory_limited); deparseAnalyzeSql(&sql, relation, method, sample_frac, &astate.retrieved_attrs); diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c index bfd3ebc601e..8295f7639cb 100644 --- a/src/backend/executor/execMain.c +++ b/src/backend/executor/execMain.c @@ -64,6 +64,9 @@ #include "utils/snapmgr.h" +/* max batch for fetching from cursor */ +int cursor_fetch_limit = 4096*1024; + /* Hooks for plugins to get control in ExecutorStart/Run/Finish/End */ ExecutorStart_hook_type ExecutorStart_hook = NULL; ExecutorRun_hook_type ExecutorRun_hook = NULL; @@ -343,6 +346,7 @@ standard_ExecutorRun(QueryDesc *queryDesc, * startup tuple receiver, if we will be emitting tuples */ estate->es_processed = 0; + estate->es_eof = false; sendTuples = (operation == CMD_SELECT || queryDesc->plannedstmt->hasReturning); @@ -1669,11 +1673,13 @@ ExecutePlan(QueryDesc *queryDesc, bool use_parallel_mode; TupleTableSlot *slot; uint64 current_tuple_count; + Size current_batch_size; /* * initialize local variables */ current_tuple_count = 0; + current_batch_size = 0; /* * Set the direction. @@ -1715,7 +1721,10 @@ ExecutePlan(QueryDesc *queryDesc, * process so we just end the loop... */ if (TupIsNull(slot)) + { + estate->es_eof = true; break; + } /* * If we have a junk filter, then project a new tuple with the junk @@ -1740,7 +1749,10 @@ ExecutePlan(QueryDesc *queryDesc, * end the loop. */ if (!dest->receiveSlot(slot, dest)) + { + estate->es_eof = true; break; + } } /* @@ -1757,8 +1769,29 @@ ExecutePlan(QueryDesc *queryDesc, * means no limit. */ current_tuple_count++; - if (numberTuples && numberTuples == current_tuple_count) - break; + if (numberTuples) + { + if (numberTuples == current_tuple_count) + break; + + /* + * If batch limit in bytes is specified, count current batch size + * and exit if limit is reached + */ + if (cursor_fetch_limit >= 0 && (estate->es_top_eflags & EXEC_FLAG_MEMORY_LIMITED)) + { + Size tuple_len; + + /* Compute length of the current tuple */ + slot_getallattrs(slot); + tuple_len = estimate_tuple_size(slot->tts_tupleDescriptor, slot->tts_values, slot->tts_isnull); + current_batch_size += tuple_len; + + if (current_batch_size > cursor_fetch_limit) + break; + } + } + } /* diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c index a7955e476f9..7f820388878 100644 --- a/src/backend/executor/execUtils.c +++ b/src/backend/executor/execUtils.c @@ -143,6 +143,7 @@ CreateExecutorState(void) estate->es_processed = 0; estate->es_total_processed = 0; + estate->es_eof = false; estate->es_top_eflags = 0; estate->es_instrument = 0; diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y index 713ee5c10a2..457c1c456ef 100644 --- a/src/backend/parser/gram.y +++ b/src/backend/parser/gram.y @@ -750,10 +750,10 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query); KEEP KEY KEYS LABEL LANGUAGE LARGE_P LAST_P LATERAL_P - LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL + LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LIMITED LISTEN LOAD LOCAL LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED LSN_P - MAPPING MATCH MATCHED MATERIALIZED MAXVALUE MERGE MERGE_ACTION METHOD + MAPPING MATCH MATCHED MATERIALIZED MAXVALUE MEMORY MERGE MERGE_ACTION METHOD MINUTE_P MINVALUE MODE MONTH_P MOVE NAME_P NAMES NATIONAL NATURAL NCHAR NESTED NEW NEXT NFC NFD NFKC NFKD NO @@ -12939,6 +12939,7 @@ cursor_options: /*EMPTY*/ { $$ = 0; } | cursor_options BINARY { $$ = $1 | CURSOR_OPT_BINARY; } | cursor_options ASENSITIVE { $$ = $1 | CURSOR_OPT_ASENSITIVE; } | cursor_options INSENSITIVE { $$ = $1 | CURSOR_OPT_INSENSITIVE; } + | cursor_options MEMORY LIMITED { $$ = $1 | CURSOR_OPT_MEMORY_LIMITED; } ; opt_hold: /* EMPTY */ { $$ = 0; } @@ -18039,6 +18040,7 @@ unreserved_keyword: | LAST_P | LEAKPROOF | LEVEL + | LIMITED | LISTEN | LOAD | LOCAL @@ -18052,6 +18054,7 @@ unreserved_keyword: | MATCHED | MATERIALIZED | MAXVALUE + | MEMORY | MERGE | METHOD | MINUTE_P @@ -18657,6 +18660,7 @@ bare_label_keyword: | LEFT | LEVEL | LIKE + | LIMITED | LISTEN | LOAD | LOCAL @@ -18672,6 +18676,7 @@ bare_label_keyword: | MATCHED | MATERIALIZED | MAXVALUE + | MEMORY | MERGE | MERGE_ACTION | METHOD diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c index d8fc75d0bb9..b6995d7e706 100644 --- a/src/backend/tcop/pquery.c +++ b/src/backend/tcop/pquery.c @@ -17,6 +17,7 @@ #include +#include "access/htup_details.h" #include "access/xact.h" #include "commands/prepare.h" #include "executor/executor.h" @@ -44,7 +45,7 @@ static void ProcessQuery(PlannedStmt *plan, QueryCompletion *qc); static void FillPortalStore(Portal portal, bool isTopLevel); static uint64 RunFromStore(Portal portal, ScanDirection direction, uint64 count, - DestReceiver *dest); + DestReceiver *dest, bool *eof); static uint64 PortalRunSelect(Portal portal, bool forward, long count, DestReceiver *dest); static void PortalRunUtility(Portal portal, PlannedStmt *pstmt, @@ -507,6 +508,8 @@ PortalStart(Portal portal, ParamListInfo params, else myeflags = eflags; + if (portal->cursorOptions & CURSOR_OPT_MEMORY_LIMITED) + myeflags |= EXEC_FLAG_MEMORY_LIMITED; /* * Call ExecutorStart to prepare the plan for execution */ @@ -864,6 +867,7 @@ PortalRunSelect(Portal portal, QueryDesc *queryDesc; ScanDirection direction; uint64 nprocessed; + bool eof; /* * NB: queryDesc will be NULL if we are fetching from a held cursor or a @@ -909,20 +913,23 @@ PortalRunSelect(Portal portal, count = 0; if (portal->holdStore) - nprocessed = RunFromStore(portal, direction, (uint64) count, dest); + { + nprocessed = RunFromStore(portal, direction, (uint64) count, dest, &eof); + } else { PushActiveSnapshot(queryDesc->snapshot); ExecutorRun(queryDesc, direction, (uint64) count); nprocessed = queryDesc->estate->es_processed; PopActiveSnapshot(); + eof = queryDesc->estate->es_eof; } if (!ScanDirectionIsNoMovement(direction)) { if (nprocessed > 0) portal->atStart = false; /* OK to go backward now */ - if (count == 0 || nprocessed < (uint64) count) + if (count == 0 || eof) portal->atEnd = true; /* we retrieved 'em all */ portal->portalPos += nprocessed; } @@ -948,13 +955,16 @@ PortalRunSelect(Portal portal, count = 0; if (portal->holdStore) - nprocessed = RunFromStore(portal, direction, (uint64) count, dest); + { + nprocessed = RunFromStore(portal, direction, (uint64) count, dest, &eof); + } else { PushActiveSnapshot(queryDesc->snapshot); ExecutorRun(queryDesc, direction, (uint64) count); nprocessed = queryDesc->estate->es_processed; PopActiveSnapshot(); + eof = queryDesc->estate->es_eof; } if (!ScanDirectionIsNoMovement(direction)) @@ -964,7 +974,7 @@ PortalRunSelect(Portal portal, portal->atEnd = false; /* OK to go forward now */ portal->portalPos++; /* adjust for endpoint case */ } - if (count == 0 || nprocessed < (uint64) count) + if (count == 0 || eof) { portal->atStart = true; /* we retrieved 'em all */ portal->portalPos = 0; @@ -1049,15 +1059,18 @@ FillPortalStore(Portal portal, bool isTopLevel) */ static uint64 RunFromStore(Portal portal, ScanDirection direction, uint64 count, - DestReceiver *dest) + DestReceiver *dest, bool *eof) { uint64 current_tuple_count = 0; + Size current_batch_size = 0; TupleTableSlot *slot; slot = MakeSingleTupleTableSlot(portal->tupDesc, &TTSOpsMinimalTuple); dest->rStartup(dest, CMD_SELECT, portal->tupDesc); + *eof = false; + if (ScanDirectionIsNoMovement(direction)) { /* do nothing except start/stop the destination */ @@ -1079,7 +1092,10 @@ RunFromStore(Portal portal, ScanDirection direction, uint64 count, MemoryContextSwitchTo(oldcontext); if (!ok) + { + *eof = true; break; + } /* * If we are not able to send the tuple, we assume the destination @@ -1087,7 +1103,24 @@ RunFromStore(Portal portal, ScanDirection direction, uint64 count, * end the loop. */ if (!dest->receiveSlot(slot, dest)) + { + *eof = true; break; + } + + /* + * If batch limit in bytes is specified, count current batch + * size. + */ + if (cursor_fetch_limit > 0 && count && (portal->cursorOptions & CURSOR_OPT_MEMORY_LIMITED)) + { + Size tuple_len; + + /* Compute length of the current tuple. */ + slot_getallattrs(slot); + tuple_len = estimate_tuple_size(slot->tts_tupleDescriptor, slot->tts_values, slot->tts_isnull); + current_batch_size += tuple_len; + } ExecClearTuple(slot); @@ -1097,8 +1130,15 @@ RunFromStore(Portal portal, ScanDirection direction, uint64 count, * means no limit. */ current_tuple_count++; - if (count && count == current_tuple_count) - break; + if (count) + { + if (count == current_tuple_count) + break; + + /* Exit if batch limit is reached */ + if (current_batch_size > cursor_fetch_limit) + break; + } } } diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat index 7c60b125564..502e965843e 100644 --- a/src/backend/utils/misc/guc_parameters.dat +++ b/src/backend/utils/misc/guc_parameters.dat @@ -522,6 +522,15 @@ assign_hook => 'assign_createrole_self_grant', }, +{ name => 'cursor_fetch_limit', type => 'int', context => 'PGC_USERSET', group => 'RESOURCES_MEM', + short_desc => 'Sets the maximum size in bytes for fetching from cursor', + flags => 'GUC_UNIT_BYTE', + variable => 'cursor_fetch_limit', + boot_val => '4194304', + min => '-1', + max => 'MaxAllocSize', +}, + { name => 'cursor_tuple_fraction', type => 'real', context => 'PGC_USERSET', group => 'QUERY_TUNING_OTHER', short_desc => 'Sets the planner\'s estimate of the fraction of a cursor\'s rows that will be retrieved.', flags => 'GUC_EXPLAIN', diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c index 73ff6ad0a32..bf40d407494 100644 --- a/src/backend/utils/misc/guc_tables.c +++ b/src/backend/utils/misc/guc_tables.c @@ -50,6 +50,7 @@ #include "commands/vacuum.h" #include "common/file_utils.h" #include "common/scram-common.h" +#include "executor/executor.h" #include "jit/jit.h" #include "libpq/auth.h" #include "libpq/libpq.h" diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index dc9e2255f8a..d0ce6f52e39 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -468,6 +468,7 @@ #default_statistics_target = 100 # range 1-10000 #constraint_exclusion = partition # on, off, or partition #cursor_tuple_fraction = 0.1 # range 0.0-1.0 +#cursor_fetch_limit = 4MB # maximum size in bytes for fetching from cursor #from_collapse_limit = 8 #jit = on # allow JIT compilation #join_collapse_limit = 8 # 1 disables collapsing of explicit diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h index 5929aabc353..ef6ff711092 100644 --- a/src/include/executor/executor.h +++ b/src/include/executor/executor.h @@ -70,7 +70,7 @@ #define EXEC_FLAG_MARK 0x0010 /* need mark/restore */ #define EXEC_FLAG_SKIP_TRIGGERS 0x0020 /* skip AfterTrigger setup */ #define EXEC_FLAG_WITH_NO_DATA 0x0040 /* REFRESH ... WITH NO DATA */ - +#define EXEC_FLAG_MEMORY_LIMITED 0x0080 /* memory limited */ /* Hook for plugins to get control in ExecutorStart() */ typedef void (*ExecutorStart_hook_type) (QueryDesc *queryDesc, int eflags); @@ -96,6 +96,8 @@ typedef bool (*ExecutorCheckPerms_hook_type) (List *rangeTable, bool ereport_on_violation); extern PGDLLIMPORT ExecutorCheckPerms_hook_type ExecutorCheckPerms_hook; +/* GUC variables */ +extern PGDLLIMPORT int cursor_fetch_limit; /* * prototypes from functions in execAmi.c diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h index 3220f9b2574..ecd0edd390c 100644 --- a/src/include/nodes/execnodes.h +++ b/src/include/nodes/execnodes.h @@ -719,6 +719,7 @@ typedef struct EState * ExecutorRun() call. */ uint64 es_total_processed; /* total # of tuples aggregated across all * ExecutorRun() calls. */ + bool es_eof; /* true if no more data to process */ int es_top_eflags; /* eflags passed to ExecutorStart */ int es_instrument; /* OR of InstrumentOption flags */ diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h index 646d6ced763..1bf77513bb6 100644 --- a/src/include/nodes/parsenodes.h +++ b/src/include/nodes/parsenodes.h @@ -3418,6 +3418,7 @@ typedef struct SecLabelStmt #define CURSOR_OPT_INSENSITIVE 0x0008 /* INSENSITIVE */ #define CURSOR_OPT_ASENSITIVE 0x0010 /* ASENSITIVE */ #define CURSOR_OPT_HOLD 0x0020 /* WITH HOLD */ +#define CURSOR_OPT_MEMORY_LIMITED 0x0040 /* MEMORY LIMITED */ /* these planner-control flags do not correspond to any SQL grammar: */ #define CURSOR_OPT_FAST_PLAN 0x0100 /* prefer fast-start plan */ #define CURSOR_OPT_GENERIC_PLAN 0x0200 /* force use of generic plan */ diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h index f7753c5c8a8..0f37469bb21 100644 --- a/src/include/parser/kwlist.h +++ b/src/include/parser/kwlist.h @@ -261,6 +261,7 @@ PG_KEYWORD("left", LEFT, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL) PG_KEYWORD("level", LEVEL, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("like", LIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL) PG_KEYWORD("limit", LIMIT, RESERVED_KEYWORD, AS_LABEL) +PG_KEYWORD("limited", LIMITED, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("listen", LISTEN, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("load", LOAD, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("local", LOCAL, UNRESERVED_KEYWORD, BARE_LABEL) @@ -276,6 +277,7 @@ PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("matched", MATCHED, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD, BARE_LABEL) +PG_KEYWORD("memory", MEMORY, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("merge", MERGE, UNRESERVED_KEYWORD, BARE_LABEL) PG_KEYWORD("merge_action", MERGE_ACTION, COL_NAME_KEYWORD, BARE_LABEL) PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD, BARE_LABEL) diff --git a/src/test/regress/expected/portals.out b/src/test/regress/expected/portals.out index 31f77abc446..c1fc04761dc 100644 --- a/src/test/regress/expected/portals.out +++ b/src/test/regress/expected/portals.out @@ -1561,3 +1561,108 @@ fetch all in held_portal; (1 row) reset default_toast_compression; +-- Check memory limit for fetching from cursor +set cursor_fetch_limit = '512B'; +BEGIN; +DECLARE foo1 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk1 ORDER BY unique2; +DECLARE foo2 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk2; +DECLARE foo3 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk1 ORDER BY unique2; +DECLARE foo4 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk2; +FETCH 1 in foo1; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 8800 | 0 | 0 | 0 | 0 | 0 | 0 | 800 | 800 | 3800 | 8800 | 0 | 1 | MAAAAA | AAAAAA | AAAAxx +(1 row) + +FETCH 2 in foo2; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 8800 | 0 | 0 | 0 | 0 | 0 | 0 | 800 | 800 | 3800 | 8800 | 0 | 1 | MAAAAA | AAAAAA | AAAAxx + 1891 | 1 | 1 | 3 | 1 | 11 | 91 | 891 | 1891 | 1891 | 1891 | 182 | 183 | TUAAAA | BAAAAA | HHHHxx +(2 rows) + +FETCH 3 in foo3; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 8800 | 0 | 0 | 0 | 0 | 0 | 0 | 800 | 800 | 3800 | 8800 | 0 | 1 | MAAAAA | AAAAAA | AAAAxx + 1891 | 1 | 1 | 3 | 1 | 11 | 91 | 891 | 1891 | 1891 | 1891 | 182 | 183 | TUAAAA | BAAAAA | HHHHxx + 3420 | 2 | 0 | 0 | 0 | 0 | 20 | 420 | 1420 | 3420 | 3420 | 40 | 41 | OBAAAA | CAAAAA | OOOOxx +(3 rows) + +-- Well, we've reached the limit +FETCH 4 in foo4; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 8800 | 0 | 0 | 0 | 0 | 0 | 0 | 800 | 800 | 3800 | 8800 | 0 | 1 | MAAAAA | AAAAAA | AAAAxx + 1891 | 1 | 1 | 3 | 1 | 11 | 91 | 891 | 1891 | 1891 | 1891 | 182 | 183 | TUAAAA | BAAAAA | HHHHxx + 3420 | 2 | 0 | 0 | 0 | 0 | 20 | 420 | 1420 | 3420 | 3420 | 40 | 41 | OBAAAA | CAAAAA | OOOOxx +(3 rows) + +-- Fetch the next batch +FETCH 4 in foo4; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 9850 | 3 | 0 | 2 | 0 | 10 | 50 | 850 | 1850 | 4850 | 9850 | 100 | 101 | WOAAAA | DAAAAA | VVVVxx + 7164 | 4 | 0 | 0 | 4 | 4 | 64 | 164 | 1164 | 2164 | 7164 | 128 | 129 | OPAAAA | EAAAAA | AAAAxx + 8009 | 5 | 1 | 1 | 9 | 9 | 9 | 9 | 9 | 3009 | 8009 | 18 | 19 | BWAAAA | FAAAAA | HHHHxx +(3 rows) + +FETCH backward 4 in foo4; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 7164 | 4 | 0 | 0 | 4 | 4 | 64 | 164 | 1164 | 2164 | 7164 | 128 | 129 | OPAAAA | EAAAAA | AAAAxx + 9850 | 3 | 0 | 2 | 0 | 10 | 50 | 850 | 1850 | 4850 | 9850 | 100 | 101 | WOAAAA | DAAAAA | VVVVxx + 3420 | 2 | 0 | 0 | 0 | 0 | 20 | 420 | 1420 | 3420 | 3420 | 40 | 41 | OBAAAA | CAAAAA | OOOOxx +(3 rows) + +-- Check cursor with hold +DECLARE foo5 MEMORY LIMITED CURSOR WITH HOLD FOR SELECT * FROM tenk2 LIMIT 30; +commit; +FETCH 5 FROM foo5; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 8800 | 0 | 0 | 0 | 0 | 0 | 0 | 800 | 800 | 3800 | 8800 | 0 | 1 | MAAAAA | AAAAAA | AAAAxx + 1891 | 1 | 1 | 3 | 1 | 11 | 91 | 891 | 1891 | 1891 | 1891 | 182 | 183 | TUAAAA | BAAAAA | HHHHxx + 3420 | 2 | 0 | 0 | 0 | 0 | 20 | 420 | 1420 | 3420 | 3420 | 40 | 41 | OBAAAA | CAAAAA | OOOOxx +(3 rows) + +FETCH 5 FROM foo5; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 9850 | 3 | 0 | 2 | 0 | 10 | 50 | 850 | 1850 | 4850 | 9850 | 100 | 101 | WOAAAA | DAAAAA | VVVVxx + 7164 | 4 | 0 | 0 | 4 | 4 | 64 | 164 | 1164 | 2164 | 7164 | 128 | 129 | OPAAAA | EAAAAA | AAAAxx + 8009 | 5 | 1 | 1 | 9 | 9 | 9 | 9 | 9 | 3009 | 8009 | 18 | 19 | BWAAAA | FAAAAA | HHHHxx +(3 rows) + +-- FETCH ALL is not limited by cursor_fetch_limit +FETCH ALL FROM foo5; + unique1 | unique2 | two | four | ten | twenty | hundred | thousand | twothousand | fivethous | tenthous | odd | even | stringu1 | stringu2 | string4 +---------+---------+-----+------+-----+--------+---------+----------+-------------+-----------+----------+-----+------+----------+----------+--------- + 5057 | 6 | 1 | 1 | 7 | 17 | 57 | 57 | 1057 | 57 | 5057 | 114 | 115 | NMAAAA | GAAAAA | OOOOxx + 6701 | 7 | 1 | 1 | 1 | 1 | 1 | 701 | 701 | 1701 | 6701 | 2 | 3 | TXAAAA | HAAAAA | VVVVxx + 4321 | 8 | 1 | 1 | 1 | 1 | 21 | 321 | 321 | 4321 | 4321 | 42 | 43 | FKAAAA | IAAAAA | AAAAxx + 3043 | 9 | 1 | 3 | 3 | 3 | 43 | 43 | 1043 | 3043 | 3043 | 86 | 87 | BNAAAA | JAAAAA | HHHHxx + 1314 | 10 | 0 | 2 | 4 | 14 | 14 | 314 | 1314 | 1314 | 1314 | 28 | 29 | OYAAAA | KAAAAA | OOOOxx + 1504 | 11 | 0 | 0 | 4 | 4 | 4 | 504 | 1504 | 1504 | 1504 | 8 | 9 | WFAAAA | LAAAAA | VVVVxx + 5222 | 12 | 0 | 2 | 2 | 2 | 22 | 222 | 1222 | 222 | 5222 | 44 | 45 | WSAAAA | MAAAAA | AAAAxx + 6243 | 13 | 1 | 3 | 3 | 3 | 43 | 243 | 243 | 1243 | 6243 | 86 | 87 | DGAAAA | NAAAAA | HHHHxx + 5471 | 14 | 1 | 3 | 1 | 11 | 71 | 471 | 1471 | 471 | 5471 | 142 | 143 | LCAAAA | OAAAAA | OOOOxx + 5006 | 15 | 0 | 2 | 6 | 6 | 6 | 6 | 1006 | 6 | 5006 | 12 | 13 | OKAAAA | PAAAAA | VVVVxx + 5387 | 16 | 1 | 3 | 7 | 7 | 87 | 387 | 1387 | 387 | 5387 | 174 | 175 | FZAAAA | QAAAAA | AAAAxx + 5785 | 17 | 1 | 1 | 5 | 5 | 85 | 785 | 1785 | 785 | 5785 | 170 | 171 | NOAAAA | RAAAAA | HHHHxx + 6621 | 18 | 1 | 1 | 1 | 1 | 21 | 621 | 621 | 1621 | 6621 | 42 | 43 | RUAAAA | SAAAAA | OOOOxx + 6969 | 19 | 1 | 1 | 9 | 9 | 69 | 969 | 969 | 1969 | 6969 | 138 | 139 | BIAAAA | TAAAAA | VVVVxx + 9460 | 20 | 0 | 0 | 0 | 0 | 60 | 460 | 1460 | 4460 | 9460 | 120 | 121 | WZAAAA | UAAAAA | AAAAxx + 59 | 21 | 1 | 3 | 9 | 19 | 59 | 59 | 59 | 59 | 59 | 118 | 119 | HCAAAA | VAAAAA | HHHHxx + 8020 | 22 | 0 | 0 | 0 | 0 | 20 | 20 | 20 | 3020 | 8020 | 40 | 41 | MWAAAA | WAAAAA | OOOOxx + 7695 | 23 | 1 | 3 | 5 | 15 | 95 | 695 | 1695 | 2695 | 7695 | 190 | 191 | ZJAAAA | XAAAAA | VVVVxx + 3442 | 24 | 0 | 2 | 2 | 2 | 42 | 442 | 1442 | 3442 | 3442 | 84 | 85 | KCAAAA | YAAAAA | AAAAxx + 5119 | 25 | 1 | 3 | 9 | 19 | 19 | 119 | 1119 | 119 | 5119 | 38 | 39 | XOAAAA | ZAAAAA | HHHHxx + 646 | 26 | 0 | 2 | 6 | 6 | 46 | 646 | 646 | 646 | 646 | 92 | 93 | WYAAAA | ABAAAA | OOOOxx + 9605 | 27 | 1 | 1 | 5 | 5 | 5 | 605 | 1605 | 4605 | 9605 | 10 | 11 | LFAAAA | BBAAAA | VVVVxx + 263 | 28 | 1 | 3 | 3 | 3 | 63 | 263 | 263 | 263 | 263 | 126 | 127 | DKAAAA | CBAAAA | AAAAxx + 3269 | 29 | 1 | 1 | 9 | 9 | 69 | 269 | 1269 | 3269 | 3269 | 138 | 139 | TVAAAA | DBAAAA | HHHHxx +(24 rows) + +CLOSE foo5; +reset cursor_fetch_limit; diff --git a/src/test/regress/sql/portals.sql b/src/test/regress/sql/portals.sql index fc4cccb96c0..6d77c89137e 100644 --- a/src/test/regress/sql/portals.sql +++ b/src/test/regress/sql/portals.sql @@ -605,3 +605,31 @@ drop table toasted_data; fetch all in held_portal; reset default_toast_compression; + +-- Check memory limit for fetching from cursor +set cursor_fetch_limit = '512B'; + +BEGIN; +DECLARE foo1 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk1 ORDER BY unique2; +DECLARE foo2 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk2; +DECLARE foo3 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk1 ORDER BY unique2; +DECLARE foo4 SCROLL MEMORY LIMITED CURSOR FOR SELECT * FROM tenk2; + +FETCH 1 in foo1; +FETCH 2 in foo2; +FETCH 3 in foo3; +-- Well, we've reached the limit +FETCH 4 in foo4; +-- Fetch the next batch +FETCH 4 in foo4; +FETCH backward 4 in foo4; + +-- Check cursor with hold +DECLARE foo5 MEMORY LIMITED CURSOR WITH HOLD FOR SELECT * FROM tenk2 LIMIT 30; +commit; +FETCH 5 FROM foo5; +FETCH 5 FROM foo5; +-- FETCH ALL is not limited by cursor_fetch_limit +FETCH ALL FROM foo5; +CLOSE foo5; +reset cursor_fetch_limit; -- 2.43.0