我有以下PostgreSQL表和触发函数来实现表的历史记录：
CREATE TABLE "ps_counters"
(
"psid" integer NOT NULL,
"counter" bigint[] NOT NULL -- This is the array of 256 counters. Upon insertion of new PS all these values must set to array of 256 bigint elements all equal to 0.
);
CREATE TABLE "ps_counters_history"
(
"id" serial PRIMARY KEY,
"timestamp" timestamp NOT NULL DEFAULT clock_timestamp(),
"psid" integer NOT NULL,
"counter" bigint[] NOT NULL
);
CREATE OR REPLACE FUNCTION ps_counters_history_trigger()
RETURNS trigger AS
$BODY$
DECLARE
table_name text;
BEGIN
table_name := 'ps_counters_history_' || to_char(CURRENT_DATE, 'yyyy_mm');
IF NOT EXISTS (SELECT 1 FROM pg_class WHERE relname = table_name)
THEN
EXECUTE 'CREATE TABLE IF NOT EXISTS ' || table_name ||
' () INHERITS (ps_counters_history);';
END IF;
EXECUTE 'INSERT INTO ' || table_name ||
'(psid, counter) VALUES ($1.psid, $1.counter);' USING NEW;
RETURN NEW;
END
$BODY$
LANGUAGE plpgsql;
CREATE TRIGGER ps_counters_history_trigger
AFTER INSERT OR UPDATE ON ps_counters FOR EACH ROW
EXECUTE PROCEDURE ps_counters_history_trigger();
对于某些超出特定限制的查询，我遇到以下错误：
[2016-12-09 11:04:28.233844] [0x00007fc72ebaa700] [error]: PlayStation (ID: 5; DallasID: MC00-0497): ERROR: payload string too long
CONTEXT: SQL statement "SELECT pg_notify('addedrecord',json_build_object('dataNew',dataNew,'dataOld',dataOld,'table',TG_TABLE_NAME,'query',TG_OP,'schema',TG_TABLE_SCHEMA )::text )"
PL/pgSQL function ps_counters_history_trigger() line 13 at PERFORM
此类查询的示例如下：
UPDATE ps_counters SET
counter[0] = 2035400,
counter[1] = 723500,
counter[2] = 5105400,
counter[3] = 750900,
counter[4] = 750900,
counter[5] = 12,
counter[6] = 10,
counter[7] = 2,
counter[8] = 0,
counter[9] = 0,
counter[10] = 0,
counter[11] = 161500,
counter[12] = 0,
counter[13] = 0,
counter[14] = 0,
counter[15] = 0,
counter[16] = 0,
counter[17] = 0,
counter[18] = 0,
counter[19] = 0,
counter[20] = 0,
counter[21] = 0,
counter[22] = 0,
counter[23] = 1901300,
counter[24] = 0,
counter[25] = 0,
counter[26] = 0,
counter[27] = 0,
counter[28] = 723500,
counter[29] = 0,
counter[30] = 0,
counter[31] = 5105400,
counter[32] = 0,
counter[33] = 0,
counter[34] = 5828900,
counter[35] = 5856300,
counter[36] = 2062800,
counter[37] = 0,
counter[38] = 12,
counter[39] = 0,
counter[40] = 0,
counter[41] = 0,
counter[42] = 0,
counter[43] = 0,
counter[44] = 0,
counter[45] = 0,
counter[46] = 1901300,
counter[47] = 0,
counter[48] = 0,
counter[49] = 0,
counter[50] = 0,
counter[51] = 0,
counter[52] = 0,
counter[53] = 0,
counter[54] = 0,
counter[55] = 0,
counter[56] = 0,
counter[57] = 0,
counter[58] = 0,
counter[59] = 0,
counter[60] = 0,
counter[61] = 0,
counter[62] = 0,
counter[63] = 0,
counter[64] = 5,
counter[65] = 0,
counter[66] = 0,
counter[67] = 6,
counter[68] = 0,
counter[69] = 0,
counter[70] = 5,
counter[71] = 5,
counter[72] = 4,
counter[73] = 0,
counter[74] = 0,
counter[75] = 0,
counter[76] = 0,
counter[77] = 0,
counter[78] = 0,
counter[79] = 0,
counter[80] = 0,
counter[81] = 0,
counter[82] = 0,
counter[83] = 0,
counter[84] = 0,
counter[85] = 0,
counter[86] = 0,
counter[87] = 0,
counter[88] = 0,
counter[89] = 0,
counter[90] = 0,
counter[91] = 0,
counter[92] = 0,
counter[93] = 0,
counter[94] = 0,
counter[95] = 0,
counter[96] = 0,
counter[97] = 0,
counter[98] = 0,
counter[99] = 0,
counter[100] = 0,
counter[101] = 0,
counter[102] = 0,
counter[103] = 0,
counter[104] = 0,
counter[105] = 0,
counter[106] = 0,
counter[107] = 0,
counter[108] = 0,
counter[109] = 0,
counter[110] = 0,
counter[111] = 0,
counter[112] = 0,
counter[113] = 0,
counter[114] = 0,
counter[115] = 0,
counter[116] = 0,
counter[117] = 0,
counter[118] = 0,
counter[119] = 0,
counter[120] = 0,
counter[121] = 0,
counter[122] = 0,
counter[123] = 0,
counter[124] = 0,
counter[125] = 0,
counter[126] = 0,
counter[127] = 0,
counter[128] = 0,
counter[129] = 0,
counter[130] = 0,
counter[131] = 0,
counter[132] = 0,
counter[133] = 0,
counter[134] = 0,
counter[135] = 0,
counter[136] = 0,
counter[137] = 0,
counter[138] = 0,
counter[139] = 0,
counter[140] = 0,
counter[141] = 0,
counter[142] = 0,
counter[143] = 0,
counter[144] = 0,
counter[145] = 0,
counter[146] = 0,
counter[147] = 0,
counter[148] = 0,
counter[149] = 0,
counter[150] = 0,
counter[151] = 0,
counter[152] = 0,
counter[153] = 0,
counter[154] = 0,
counter[155] = 0,
counter[156] = 0,
counter[157] = 0,
counter[158] = 0,
counter[159] = 0,
counter[160] = 0,
counter[161] = 0,
counter[162] = 0,
counter[163] = 0,
counter[164] = 0,
counter[165] = 0,
counter[166] = 0,
counter[167] = 0,
counter[168] = 0,
counter[169] = 0,
counter[170] = 0,
counter[171] = 0,
counter[172] = 0,
counter[173] = 0,
counter[174] = 0,
counter[175] = 0,
counter[176] = 0,
counter[177] = 0,
counter[178] = 0,
counter[179] = 0,
counter[180] = 0,
counter[181] = 0,
counter[182] = 0,
counter[183] = 0,
counter[184] = 0,
counter[185] = 0,
counter[186] = 0,
counter[187] = 0,
counter[188] = 0,
counter[189] = 0,
counter[190] = 0,
counter[191] = 0,
counter[192] = 2035400,
counter[193] = 0,
counter[194] = 2035400,
counter[195] = 0,
counter[196] = 2,
counter[197] = 0,
counter[198] = 0,
counter[199] = 0,
counter[200] = 0,
counter[201] = 0,
counter[202] = 0,
counter[203] = 0,
counter[204] = 0,
counter[205] = 0,
counter[206] = 0,
counter[207] = 0,
counter[208] = 0,
counter[209] = 0,
counter[210] = 0,
counter[211] = 0,
counter[212] = 0,
counter[213] = 0,
counter[214] = 0,
counter[215] = 0,
counter[216] = 0,
counter[217] = 0,
counter[218] = 0,
counter[219] = 0,
counter[220] = 0,
counter[221] = 0,
counter[222] = 0,
counter[223] = 0,
counter[224] = 0,
counter[225] = 0,
counter[226] = 0,
counter[227] = 0,
counter[228] = 0,
counter[229] = 0,
counter[230] = 0,
counter[231] = 0,
counter[232] = 0,
counter[233] = 0,
counter[234] = 0,
counter[235] = 0,
counter[236] = 0,
counter[237] = 0,
counter[238] = 0,
counter[239] = 0,
counter[240] = 0,
counter[241] = 0,
counter[242] = 0,
counter[243] = 0,
counter[244] = 0,
counter[245] = 0,
counter[246] = 0,
counter[247] = 0,
counter[248] = 0,
counter[249] = 0,
counter[250] = 1901300,
counter[251] = 0,
counter[252] = 0,
counter[253] = 0,
counter[254] = 0,
counter[255] = 0
WHERE psid = 5;
我发现max notify有效载荷有8000个字节的限制。我没有直接在触发器功能中使用notify，但似乎有些操作员间接使用它。
是否可以通过某种解决方法来克服此限制？
答案 0 :(得分：3)
不幸的是，8000似乎是硬限制 - https://www.postgresql.org/docs/9.4/static/sql-notify.html
payload
The "payload" string to be communicated along with the notification.
This must be specified as a simple string literal.
In the default configuration it must be shorter than 8000 bytes.
(If binary data or large amounts of information need to be communicated,
it's best to put it in a database table and send the key of the record.)
另见 - https://github.com/xstevens/pg_kafka
Before implementing this project I had looked into LISTEN/NOTIFY operations in PostgreSQL. NOTIFY is unfortunately limited to 8000 bytes for the total payload size. I also found several mentions in the PostgreSQL mailing lists that NOTIFY was never intended to send row data; rather it was intended to get change notifications on keys to clean up external caching, etc.