diff options
| -rw-r--r-- | src/backend/nodes/outfuncs.c | 8 | ||||
| -rw-r--r-- | src/backend/nodes/readfuncs.c | 4 | ||||
| -rw-r--r-- | src/man/create_sequence.l | 85 |
3 files changed, 60 insertions, 37 deletions
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c index a8746470bf9..d99fefd03d0 100644 --- a/src/backend/nodes/outfuncs.c +++ b/src/backend/nodes/outfuncs.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/nodes/outfuncs.c,v 1.38 1998/07/13 21:27:58 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/nodes/outfuncs.c,v 1.39 1998/07/14 01:45:24 momjian Exp $ * * NOTES * Every (plan) node in POSTGRES has an associated "out" routine which @@ -660,10 +660,7 @@ _outResdom(StringInfo str, Resdom *node) sprintf(buf, " :restypmod %d ", node->restypmod); appendStringInfo(str, buf); appendStringInfo(str, " :resname "); - if (*node->resname) - sprintf(buf,"\"%s\"", node->resname); /* fix for SELECT col AS "my name" */ - else - buf[0] = '\0'; + sprintf(buf,"\"%s\"", node->resname); /* fix for SELECT col AS "my name" */ appendStringInfo(str, buf); sprintf(buf, " :reskey %d ", node->reskey); appendStringInfo(str, buf); @@ -1506,7 +1503,6 @@ _outDatum(StringInfo str, Datum value, Oid type) appendStringInfo(str, buf); } } - } static void diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c index 514d0a09c95..fc697d394e2 100644 --- a/src/backend/nodes/readfuncs.c +++ b/src/backend/nodes/readfuncs.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.30 1998/06/15 19:28:33 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/nodes/readfuncs.c,v 1.31 1998/07/14 01:45:24 momjian Exp $ * * NOTES * Most of the read functions for plan nodes are tested. (In fact, they @@ -716,7 +716,7 @@ _readResdom() else { local_node->resname = (char *) palloc(length + 1); - StrNCpy(local_node->resname, token, length + 1); + StrNCpy(local_node->resname, token+1, length + 1 - 2);/* strip quotes */ } token = lsptok(NULL, &length); /* eat :reskey */ diff --git a/src/man/create_sequence.l b/src/man/create_sequence.l index af30a0e1ebe..0a695fa6bf4 100644 --- a/src/man/create_sequence.l +++ b/src/man/create_sequence.l @@ -1,7 +1,7 @@ .\" This is -*-nroff-*- .\" XXX standard disclaimer belongs here.... -.\" $Header: /cvsroot/pgsql/src/man/Attic/create_sequence.l,v 1.4 1998/06/23 17:52:32 momjian Exp $ -.TH "CREATE SEQUENCE" SQL 04/01/97 PostgreSQL PostgreSQL +.\" $Header: /cvsroot/pgsql/src/man/Attic/create_sequence.l,v 1.5 1998/07/14 01:45:25 momjian Exp $ +.TH "CREATE SEQUENCE" SQL 07/13/98 PostgreSQL PostgreSQL .SH NAME create sequence - create a new sequence number generator .SH SYNOPSIS @@ -17,7 +17,7 @@ create sequence - create a new sequence number generator .SH DESCRIPTION .BR "Create sequence" will enter a new sequence number generator into the current data base. -Actually, new single block +Actually, a new single-record .BR table with name .IR seqname @@ -26,23 +26,23 @@ The generator will be \*(lqowned\*(rq by the user issuing the command. .PP The -.BR "increment" -is optional clause. Positive value will make ascending sequence, +.BR increment +clause is optional. A positive value will make an ascending sequence, negative - descending. Default value is 1. .PP The optional integer .BR minvalue -determines the minimum value a sequence can be. Defaults are +determines the minimum value the sequence can generate. Defaults are 1/-2147483647 for ascending/descending sequences. .PP -Use optional integer +The optional integer .BR maxvalue -to determine the maximum value for sequence. Defaults are +determines the maximum value the sequence can generate. Defaults are 2147483647/-1 for ascending/descending sequences. .PP -The optinal -.BR "start" -value enables sequence to begin anywhere. Default is +The optional +.BR start +value sets the first value to be generated. Default is .BR minvalue for ascending sequences and .BR maxvalue @@ -52,14 +52,12 @@ The .BR cache option enables sequence numbers to be preallocated and stored in memory for faster access. The minimum value is 1 -(i.e. - no cache) and it is default. -.BR NOTE: -each backend uses own cache to store allocated numbers. -Cached but not used in current session numbers will be lost. +(one value will be allocated at a time, i.e., no cache) +and that is the default. See below for details. .PP The optional .BR cycle -keyword may be used to enable sequence to continue when the +keyword may be used to enable the sequence to continue after the .BR maxvalue/minvalue has been reached by ascending/descending sequence. If the limit is reached, the next number generated will be @@ -67,27 +65,56 @@ whatever the .BR minvalue/maxvalue is. .PP -After sequence created, You may use function +After a sequence object has been created, you may use the function .BR nextval -with sequence name as argument to get new number from sequence -specified. -Function +with the sequence name as argument to generate a new number from the +specified sequence. +.PP +The function .BR currval ('sequence_name') -may be used to determine number returned by last call to +may be used to re-fetch the number returned by the last call to .BR nextval -for specified sequence in current session. +for the specified sequence in the current session. +.BR NOTE: +currval will return an error if nextval has never been called for the +given sequence in the current backend session. Also beware that it +does not give the last number ever allocated, only the last one allocated +by this backend. .PP +Use a query like .nf -Use query like - -select * from <sequence_name>; - -to get parameters of a sequence. +SELECT * FROM <sequence_name>; .fi +to get the parameters of a sequence. Aside from fetching the original +parameters, you can use +.nf +SELECT last_value FROM <sequence_name>; +.fi +to obtain the last value allocated by any backend. .PP -Low-level locking is used to enable multiple simultaneous calls -to a generator. +Low-level locking is used to ensure that multiple backends can safely use +a sequence object concurrently. +.PP +.BR NOTE: +Unexpected results may be obtained if a cache setting greater than one +is used for a sequence object that will be used concurrently by multiple +backends. Each backend will allocate "cache" successive sequence values +during one access to the sequence object and increase the sequence +object's last_value accordingly. Then, the next cache-1 uses of nextval +within that backend simply return the preallocated values without touching +the shared object. So, numbers allocated but not used in the current session +will be lost. Furthermore, although multiple backends are guaranteed to +allocate distinct sequence values, the values may be generated out of +sequence when all the backends are considered. (For example, with a cache +setting of 10, backend A might reserve values 1..10 and return nextval=1, then +backend B might reserve values 11..20 and return nextval=11 before backend +A has generated nextval=2.) Thus, with a cache setting of one it is safe +to assume that nextval values are generated sequentially; with a cache +setting greater than one you should only assume that the nextval values +are all distinct, not that they are generated purely sequentially. +Also, last_value will reflect the latest value reserved by any backend, +whether or not it has yet been returned by nextval. .PP .SH EXAMPLES .nf |