From f8f567cff5e18bfaa09ed8757783803a5a160050 Mon Sep 17 00:00:00 2001 From: mj Date: Wed, 26 Sep 2001 01:52:35 +0000 Subject: [PATCH] First version of the dupe prevention trigger. Works for INSERTs and UPDATEs. --- dbscripts/create_pg.sql | 1 + dbscripts/dupetrigger/INSTALL | 9 ++ dbscripts/dupetrigger/Makefile | 21 ++++ dbscripts/dupetrigger/README | 16 +++ dbscripts/dupetrigger/postgresql.sript | 5 + dbscripts/dupetrigger/trigger.c | 209 +++++++++++++++++++++++++++++++++ 6 files changed, 261 insertions(+) create mode 100755 dbscripts/dupetrigger/INSTALL create mode 100755 dbscripts/dupetrigger/Makefile create mode 100755 dbscripts/dupetrigger/README create mode 100755 dbscripts/dupetrigger/postgresql.sript create mode 100755 dbscripts/dupetrigger/trigger.c diff --git a/dbscripts/create_pg.sql b/dbscripts/create_pg.sql index 86bd6874..57a7ff4b 100755 --- a/dbscripts/create_pg.sql +++ b/dbscripts/create_pg.sql @@ -292,6 +292,7 @@ CREATE TABLE "comment" ( "to_language" integer DEFAULT '0' NOT NULL, "to_media" integer NOT NULL, "to_comment_status" smallint, + "checksum" integer, Constraint "comment_pkey" Primary Key ("id") ); diff --git a/dbscripts/dupetrigger/INSTALL b/dbscripts/dupetrigger/INSTALL new file mode 100755 index 00000000..8571231f --- /dev/null +++ b/dbscripts/dupetrigger/INSTALL @@ -0,0 +1,9 @@ +To install the trigger do the following: + +# make +(This makes the trigger binary and places it in /tmp with permissions 644) + +# psql -U postgres Mir < postgresql.script +(This installs the the trigger binary and creates a new trigger.) + +# rm /tmp/trigger.so diff --git a/dbscripts/dupetrigger/Makefile b/dbscripts/dupetrigger/Makefile new file mode 100755 index 00000000..ad1c52c7 --- /dev/null +++ b/dbscripts/dupetrigger/Makefile @@ -0,0 +1,21 @@ +# Makefile + +CC=gcc +PGINC=/usr/include/postgresql + +trigger.so: trigger.o + $(CC) -shared -dynamic -o trigger.so trigger.o + cp trigger.so /tmp + chmod 755 /tmp/trigger.so + +trigger.o: trigger.c + $(CC) -I$(PGINC) -c trigger.c -o trigger.o + + +clean: + rm -rf trigger.o trigger.so + + +tidy: clean + rm -rf *~ + \ No newline at end of file diff --git a/dbscripts/dupetrigger/README b/dbscripts/dupetrigger/README new file mode 100755 index 00000000..58561771 --- /dev/null +++ b/dbscripts/dupetrigger/README @@ -0,0 +1,16 @@ +Dupe check Trigger +by Matthias "Trigger Hippy" Jordan + +The files in this directory are needed to create a PostgreSQL trigger that +is used to ensure that no comment and no article is posted twice. This +happens very often by accident and is very disturbing so we have to prevent +this somehow. Because Indymedia databases will hopefully grow big very fast, +we want to do this check as fast as possible. + +So Mir simply issues the INSERT. By this INSERT statement, a trigger gets, +well, triggered that calculate a CRC-32 checksum of the comment and searches +for rows with the same checksum. If it finds the checksum, the INSERT gets +aborted. If the checksum isn't found, it is appended to the row and the +INSERT is executed. + +The trigger works for INSERTs and UPDATEs. diff --git a/dbscripts/dupetrigger/postgresql.sript b/dbscripts/dupetrigger/postgresql.sript new file mode 100755 index 00000000..d1f43c44 --- /dev/null +++ b/dbscripts/dupetrigger/postgresql.sript @@ -0,0 +1,5 @@ +\connect - postgres +DROP FUNCTION dupecheck(); +DROP TRIGGER dupetrigger ON comment; +CREATE FUNCTION dupecheck() RETURNS OPAQUE AS '/tmp/trigger.so' LANGUAGE 'C'; +CREATE TRIGGER dupetrigger BEFORE INSERT OR UPDATE ON comment FOR EACH ROW EXECUTE PROCEDURE dupecheck(); diff --git a/dbscripts/dupetrigger/trigger.c b/dbscripts/dupetrigger/trigger.c new file mode 100755 index 00000000..66f61e18 --- /dev/null +++ b/dbscripts/dupetrigger/trigger.c @@ -0,0 +1,209 @@ +// +// +// This File contructs a PostgreSQL trigger. +// The trigger is fired BEFORE an INSERT or UPDATE of an article +// or comment. It first calculates a CRC32 checksum of the row to be +// inserted or updated and checks whether there exists already another +// row with the same checksum and the same content. In this case, +// the trigger returns NULL and thus, aborts the SQL command. +// +// Author: Matthias Jordan +// + + +#include "executor/spi.h" +#include "commands/trigger.h" +#include "string.h" + +extern Datum dupecheck(PG_FUNCTION_ARGS); + +PG_FUNCTION_INFO_V1(dupecheck); + + + + +// +// +// CRC32 stuff +// + +// crc32 table based on the following polynom +#define CRC32_POLY 0x04c11db7 /* AUTODIN II, Ethernet, & FDDI */ + +u_long crc32_table[256] = + {0x0000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b, + 0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61, + 0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd, 0x4c11db70, 0x48d0c6c7, + 0x4593e01e, 0x4152fda9, 0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75, + 0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3, + 0x709f7b7a, 0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039, + 0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58, 0xbaea46ef, + 0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d, + 0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49, 0xc7361b4c, 0xc3f706fb, + 0xceb42022, 0xca753d95, 0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1, + 0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0, + 0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072, + 0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, 0x018aeb13, 0x54bf6a4, + 0x0808d07d, 0x0cc9cdca, 0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde, + 0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08, + 0x571d7dd1, 0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba, + 0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b, 0xbb60adfc, + 0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6, + 0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a, 0xe0b41de7, 0xe4750050, + 0xe9362689, 0xedf73b3e, 0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2, + 0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34, + 0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637, + 0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb, 0x4f040d56, 0x4bc510e1, + 0x46863638, 0x42472b8f, 0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53, + 0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5, + 0x3f9b762c, 0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0xe56f0ff, + 0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e, 0xf5ee4bb9, + 0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b, + 0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f, 0xc423cd6a, 0xc0e2d0dd, + 0xcda1f604, 0xc960ebb3, 0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7, + 0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71, + 0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3, + 0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640, 0x4e8ee645, 0x4a4ffbf2, + 0x470cdd2b, 0x43cdc09c, 0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8, + 0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e, + 0x18197087, 0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0xfdc1bec, + 0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d, 0x2056cd3a, + 0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0, + 0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c, 0xe3a1cbc1, 0xe760d676, + 0xea23f0af, 0xeee2ed18, 0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4, + 0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662, + 0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668, + 0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4}; + + +static u_long crc32(u_char *buf, unsigned len) +{ + u_char *p; + u_long crc; + + crc = 0xffffffff; /* preload shift register, per CRC-32 spec */ + for (p = buf; len > 0; ++p, --len) + { + crc = (crc << 8) ^ crc32_table[(crc >> 24) ^ *p]; + } + return ~crc; /* transmit complement, per CRC-32 spec */ +} /* crc32 */ + + + + + +// +// +// Trigger stuff +// + + + + +Datum dupecheck(PG_FUNCTION_ARGS) +{ + TriggerData *trigdata = (TriggerData *) fcinfo->context; + TupleDesc tupdesc; + HeapTuple rettuple; + bool isnull; + int ret = 0, i, fnumber; + long rowstrlen = 0, + crc; + int maxitems = 3, + num; + char *items[maxitems], + *rowstring, + *query; + + + /* Make sure trigdata is pointing at what I expect */ + if (!CALLED_AS_TRIGGER(fcinfo)) + elog(ERROR, "dupecheck: not fired by trigger manager"); + + /* tuple to return to Executor */ + if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event)) + rettuple = trigdata->tg_newtuple; + else + rettuple = trigdata->tg_trigtuple; + + if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event)) + return PointerGetDatum(NULL); + + tupdesc = trigdata->tg_relation->rd_att; + + /* Connect to SPI manager */ + if ((ret = SPI_connect()) < 0) + ret = SPI_connect(); + elog(NOTICE, "dupecheck: SPI_connect returned %d", ret); + + // Now we are connected to the database's SPI manager + // We will now construct a string of some important row values. + // First, we determine how long the string will be to allocate memory + // To include an additional item, add another SPI_getvalue line and + // increase maxitems above by 1 + + items[0] = SPI_getvalue(rettuple, tupdesc, SPI_fnumber(tupdesc, "creator")); + items[1] = SPI_getvalue(rettuple, tupdesc, SPI_fnumber(tupdesc, "title")); + items[2] = SPI_getvalue(rettuple, tupdesc, SPI_fnumber(tupdesc, "description")); + + for (i=0; (i < maxitems); i++) + { + rowstrlen += strlen(items[i]); + } + rowstrlen++; // add space for 0-terminator + + rowstring = malloc(rowstrlen); + if (rowstring == NULL) + { + // Big problem. + return PointerGetDatum(NULL); + } + + *rowstring = 0; + for (i=0; (i < maxitems); i++) + { + strcat(rowstring, items[i]); + } + + // rowstring now contains the data of the maxitems important + // items of the table record. Now we calculate the CRC-32 checksum + // of the rowstring + + crc = crc32(rowstring, rowstrlen - 1); + + // Now we allocate some space and construct the SQL query + query = malloc(47 + 11 + 2 + 1); // SELECT part + crc32 + "';" + 0-term + if (query == NULL) + { + // Big problem + return PointerGetDatum(NULL); + } + + sprintf(query, "SELECT count(*) FROM comment WHERE checksum='%ld';", crc); + ret = SPI_exec(query, 2); + num = SPI_getbinval(SPI_tuptable->vals[0], SPI_tuptable->tupdesc, 1, &isnull); + + if ((ret == SPI_OK_SELECT) && (num > 0)) + { + elog(NOTICE, "dupecheck: UBD prevented (dupe dropped)"); + return PointerGetDatum(NULL); + } + else + { + // The checksum wasn't found. So we modify the tuple to be + // inserted and add the fresh checksum. + int attnum; + Datum value; + char nulls = 0; + + elog(NOTICE, "dupecheck: Adding checksum to INSERT"); + attnum = SPI_fnumber(tupdesc, "checksum"); + value = (Datum) crc; + rettuple = SPI_modifytuple(trigdata->tg_relation, rettuple, 1, &attnum, &value, &nulls); + } + + SPI_finish(); + return PointerGetDatum(rettuple); +} + -- 2.11.0