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Commitf8e5f15

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Rearm statement_timeout after each executed query.
Previously statement_timeout, in the extended protocol, affected allmessages till a Sync message. For clients that pipeline/batch queryexecution that's problematic.Instead disable timeout after each Execute message, and enable, ifnecessary, the timer in start_xact_command(). As that's done only forExecute and not Parse / Bind, pipelining the latter two could stillcause undesirable timeouts. But a survey of protocol implementationsshows that all drivers issue Sync messages when preparing, and addingtimeout rearming to both is fairly expensive for the common parse /bind / execute sequence.Author: Tatsuo Ishii, editorialized by Andres FreundReviewed-By: Takayuki Tsunakawa, Andres FreundDiscussion:https://postgr.es/m/20170222.115044.1665674502985097185.t-ishii@sraoss.co.jp
1 parent0fb9e4a commitf8e5f15

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+65
-12
lines changed

1 file changed

+65
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‎src/backend/tcop/postgres.c

Lines changed: 65 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -143,6 +143,11 @@ static bool DoingCommandRead = false;
143143
staticbooldoing_extended_query_message= false;
144144
staticboolignore_till_sync= false;
145145

146+
/*
147+
* Flag to keep track of whether statement timeout timer is active.
148+
*/
149+
staticboolstmt_timeout_active= false;
150+
146151
/*
147152
* If an unnamed prepared statement exists, it's stored here.
148153
* We keep it separate from the hashtable kept by commands/prepare.c
@@ -182,6 +187,8 @@ static bool IsTransactionExitStmtList(List *pstmts);
182187
staticboolIsTransactionStmtList(List*pstmts);
183188
staticvoiddrop_unnamed_stmt(void);
184189
staticvoidlog_disconnections(intcode,Datumarg);
190+
staticvoidenable_statement_timeout(void);
191+
staticvoiddisable_statement_timeout(void);
185192

186193

187194
/* ----------------------------------------------------------------
@@ -1241,7 +1248,8 @@ exec_parse_message(const char *query_string,/* string to execute */
12411248
/*
12421249
* Start up a transaction command so we can run parse analysis etc. (Note
12431250
* that this will normally change current memory context.) Nothing happens
1244-
* if we are already in one.
1251+
* if we are already in one. This also arms the statement timeout if
1252+
* necessary.
12451253
*/
12461254
start_xact_command();
12471255

@@ -1529,7 +1537,8 @@ exec_bind_message(StringInfo input_message)
15291537
/*
15301538
* Start up a transaction command so we can call functions etc. (Note that
15311539
* this will normally change current memory context.) Nothing happens if
1532-
* we are already in one.
1540+
* we are already in one. This also arms the statement timeout if
1541+
* necessary.
15331542
*/
15341543
start_xact_command();
15351544

@@ -2021,6 +2030,9 @@ exec_execute_message(const char *portal_name, long max_rows)
20212030
* those that start or end a transaction block.
20222031
*/
20232032
CommandCounterIncrement();
2033+
2034+
/* full command has been executed, reset timeout */
2035+
disable_statement_timeout();
20242036
}
20252037

20262038
/* Send appropriate CommandComplete to client */
@@ -2450,25 +2462,27 @@ start_xact_command(void)
24502462
{
24512463
StartTransactionCommand();
24522464

2453-
/* Set statement timeout running, if any */
2454-
/* NB: this mustn't be enabled until we are within an xact */
2455-
if (StatementTimeout>0)
2456-
enable_timeout_after(STATEMENT_TIMEOUT,StatementTimeout);
2457-
else
2458-
disable_timeout(STATEMENT_TIMEOUT, false);
2459-
24602465
xact_started= true;
24612466
}
2467+
2468+
/*
2469+
* Start statement timeout if necessary. Note that this'll intentionally
2470+
* not reset the clock on an already started timeout, to avoid the timing
2471+
* overhead when start_xact_command() is invoked repeatedly, without an
2472+
* interceding finish_xact_command() (e.g. parse/bind/execute). If that's
2473+
* not desired, the timeout has to be disabled explicitly.
2474+
*/
2475+
enable_statement_timeout();
24622476
}
24632477

24642478
staticvoid
24652479
finish_xact_command(void)
24662480
{
2481+
/* cancel active statement timeout after each command */
2482+
disable_statement_timeout();
2483+
24672484
if (xact_started)
24682485
{
2469-
/* Cancel any active statement timeout before committing */
2470-
disable_timeout(STATEMENT_TIMEOUT, false);
2471-
24722486
CommitTransactionCommand();
24732487

24742488
#ifdefMEMORY_CONTEXT_CHECKING
@@ -4537,3 +4551,42 @@ log_disconnections(int code, Datum arg)
45374551
port->user_name,port->database_name,port->remote_host,
45384552
port->remote_port[0] ?" port=" :"",port->remote_port)));
45394553
}
4554+
4555+
/*
4556+
* Start statement timeout timer, if enabled.
4557+
*
4558+
* If there's already a timeout running, don't restart the timer. That
4559+
* enables compromises between accuracy of timeouts and cost of starting a
4560+
* timeout.
4561+
*/
4562+
staticvoid
4563+
enable_statement_timeout(void)
4564+
{
4565+
/* must be within an xact */
4566+
Assert(xact_started);
4567+
4568+
if (StatementTimeout>0)
4569+
{
4570+
if (!stmt_timeout_active)
4571+
{
4572+
enable_timeout_after(STATEMENT_TIMEOUT,StatementTimeout);
4573+
stmt_timeout_active= true;
4574+
}
4575+
}
4576+
else
4577+
disable_timeout(STATEMENT_TIMEOUT, false);
4578+
}
4579+
4580+
/*
4581+
* Disable statement timeout, if active.
4582+
*/
4583+
staticvoid
4584+
disable_statement_timeout(void)
4585+
{
4586+
if (stmt_timeout_active)
4587+
{
4588+
disable_timeout(STATEMENT_TIMEOUT, false);
4589+
4590+
stmt_timeout_active= false;
4591+
}
4592+
}

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