--- /dev/null
+/*-------------------------------------------------------------------------
+ *
+ * sequence.c--
+ * PostgreSQL sequences support code.
+ *
+ *-------------------------------------------------------------------------
+ */
+#include <stdio.h>
+#include <string.h>
+
+#include <postgres.h>
+
+#include <storage/bufmgr.h>
+#include <storage/bufpage.h>
+#include <storage/lmgr.h>
+#include <access/heapam.h>
+#include <nodes/parsenodes.h>
+#include <commands/creatinh.h>
+#include <commands/sequence.h>
+#include <utils/builtins.h>
+
+#define SEQ_MAGIC 0x1717
+
+#define SEQ_MAXVALUE ((int4)0x7FFFFFFF)
+#define SEQ_MINVALUE -(SEQ_MAXVALUE)
+
+bool ItsSequenceCreation = false;
+
+typedef struct FormData_pg_sequence {
+ NameData sequence_name;
+ int4 last_value;
+ int4 increment_by;
+ int4 max_value;
+ int4 min_value;
+ int4 cache_value;
+ char is_cycled;
+ char is_called;
+} FormData_pg_sequence;
+
+typedef FormData_pg_sequence *SequenceTupleForm;
+
+typedef struct sequence_magic {
+ uint32 magic;
+} sequence_magic;
+
+typedef struct SeqTableData {
+ char *name;
+ Oid relid;
+ Relation rel;
+ int4 cached;
+ int4 last;
+ int4 increment;
+ struct SeqTableData *next;
+} SeqTableData;
+
+typedef SeqTableData *SeqTable;
+
+static SeqTable seqtab = NULL;
+
+static SeqTable init_sequence (char *caller, char *name);
+static SequenceTupleForm read_info (char * caller, SeqTable elm, Buffer * buf);
+static void init_params (CreateSeqStmt *seq, SequenceTupleForm new);
+static int get_param (DefElem *def);
+
+/*
+ * DefineSequence --
+ * Creates a new sequence relation
+ */
+void
+DefineSequence (CreateSeqStmt *seq)
+{
+ FormData_pg_sequence new;
+ CreateStmt *stmt = makeNode (CreateStmt);
+ ColumnDef *coldef;
+ TypeName *typnam;
+ Relation rel;
+ Buffer buf;
+ PageHeader page;
+ sequence_magic *sm;
+ HeapTuple tuple;
+ TupleDesc tupDesc;
+ Datum value[SEQ_COL_LASTCOL];
+ char null[SEQ_COL_LASTCOL];
+ int i;
+
+ /* Check and set values */
+ init_params (seq, &new);
+
+ /*
+ * Create relation (and fill null[] & value[])
+ */
+ stmt->tableElts = NIL;
+ for (i = SEQ_COL_FIRSTCOL; i <= SEQ_COL_LASTCOL; i++)
+ {
+ typnam = makeNode(TypeName);
+ typnam->setof = FALSE;
+ typnam->arrayBounds = NULL;
+ coldef = makeNode(ColumnDef);
+ coldef->typename = typnam;
+ null[i-1] = ' ';
+
+ switch (i)
+ {
+ case SEQ_COL_NAME:
+ typnam->name = "name";
+ coldef->colname = "sequence_name";
+ value[i-1] = PointerGetDatum (seq->seqname);
+ break;
+ case SEQ_COL_LASTVAL:
+ typnam->name = "int4";
+ coldef->colname = "last_value";
+ value[i-1] = Int32GetDatum (new.last_value);
+ break;
+ case SEQ_COL_INCBY:
+ typnam->name = "int4";
+ coldef->colname = "increment_by";
+ value[i-1] = Int32GetDatum (new.increment_by);
+ break;
+ case SEQ_COL_MAXVALUE:
+ typnam->name = "int4";
+ coldef->colname = "max_value";
+ value[i-1] = Int32GetDatum (new.max_value);
+ break;
+ case SEQ_COL_MINVALUE:
+ typnam->name = "int4";
+ coldef->colname = "min_value";
+ value[i-1] = Int32GetDatum (new.min_value);
+ break;
+ case SEQ_COL_CACHE:
+ typnam->name = "int4";
+ coldef->colname = "cache_value";
+ value[i-1] = Int32GetDatum (new.cache_value);
+ break;
+ case SEQ_COL_CYCLE:
+ typnam->name = "char";
+ coldef->colname = "is_cycled";
+ value[i-1] = CharGetDatum (new.is_cycled);
+ break;
+ case SEQ_COL_CALLED:
+ typnam->name = "char";
+ coldef->colname = "is_called";
+ value[i-1] = CharGetDatum ('f');
+ break;
+ }
+ stmt->tableElts = lappend (stmt->tableElts, coldef);
+ }
+
+ stmt->relname = seq->seqname;
+ stmt->archiveLoc = -1; /* default */
+ stmt->archiveType = ARCH_NONE;
+ stmt->inhRelnames = NIL;
+
+ ItsSequenceCreation = true; /* hack */
+
+ DefineRelation (stmt);
+
+ /* Xact abort calls CloseSequences, which turns ItsSequenceCreation off */
+ ItsSequenceCreation = false; /* hack */
+
+ rel = heap_openr (seq->seqname);
+ Assert ( RelationIsValid (rel) );
+
+ RelationSetLockForWrite (rel);
+
+ tupDesc = RelationGetTupleDescriptor(rel);
+
+ Assert ( RelationGetNumberOfBlocks (rel) == 0 );
+ buf = ReadBuffer (rel, P_NEW);
+
+ if ( !BufferIsValid (buf) )
+ elog (WARN, "DefineSequence: ReadBuffer failed");
+
+ page = (PageHeader) BufferGetPage (buf);
+
+ PageInit((Page)page, BufferGetPageSize(buf), sizeof(sequence_magic));
+ sm = (sequence_magic *) PageGetSpecialPointer (page);
+ sm->magic = SEQ_MAGIC;
+
+ /* Now - form & insert sequence tuple */
+ tuple = heap_formtuple (tupDesc, value, null);
+ heap_insert (rel, tuple);
+
+ if ( WriteBuffer (buf) == STATUS_ERROR )
+ elog (WARN, "DefineSequence: WriteBuffer failed");
+
+ RelationUnsetLockForWrite (rel);
+ heap_close (rel);
+
+ return;
+
+}
+
+
+int4
+nextval (struct varlena * seqin)
+{
+ char *seqname = textout(seqin);
+ SeqTable elm;
+ Buffer buf;
+ SequenceTupleForm seq;
+ ItemPointerData iptr;
+ int4 incby, maxv, minv, cache;
+ int4 result, next, rescnt = 0;
+
+ /* open and WIntentLock sequence */
+ elm = init_sequence ("nextval", seqname);
+
+ if ( elm->last != elm->cached ) /* some numbers were cached */
+ {
+ elm->last += elm->increment;
+ return (elm->last);
+ }
+
+ seq = read_info ("nextval", elm, &buf); /* lock page and read tuple */
+
+ next = result = seq->last_value;
+ incby = seq->increment_by;
+ maxv = seq->max_value;
+ minv = seq->min_value;
+ cache = seq->cache_value;
+
+ if ( seq->is_called != 't' )
+ rescnt++; /* last_value if not called */
+
+ while ( rescnt < cache ) /* try to fetch cache numbers */
+ {
+ /*
+ * Check MAXVALUE for ascending sequences
+ * and MINVALUE for descending sequences
+ */
+ if ( incby > 0 ) /* ascending sequence */
+ {
+ if ( ( maxv >= 0 && next > maxv - incby) ||
+ ( maxv < 0 && next + incby > maxv ) )
+ {
+ if ( rescnt > 0 )
+ break; /* stop caching */
+ if ( seq->is_cycled != 't' )
+ elog (WARN, "%s.nextval: got MAXVALUE (%d)",
+ seqname, maxv);
+ next = minv;
+ }
+ else
+ next += incby;
+ }
+ else /* descending sequence */
+ {
+ if ( ( minv < 0 && next < minv - incby ) ||
+ ( minv >= 0 && next + incby < minv ) )
+ {
+ if ( rescnt > 0 )
+ break; /* stop caching */
+ if ( seq->is_cycled != 't' )
+ elog (WARN, "%s.nextval: got MINVALUE (%d)",
+ seqname, minv);
+ next = maxv;
+ }
+ else
+ next += incby;
+ }
+ rescnt++; /* got result */
+ if ( rescnt == 1 ) /* if it's first one - */
+ result = next; /* it's what to return */
+ }
+
+ /* save info in local cache */
+ elm->last = result; /* last returned number */
+ elm->cached = next; /* last cached number */
+
+ /* save info in sequence relation */
+ seq->last_value = next; /* last fetched number */
+ seq->is_called = 't';
+
+ if ( WriteBuffer (buf) == STATUS_ERROR )
+ elog (WARN, "%s.nextval: WriteBuffer failed", elm->name);
+
+ ItemPointerSet(&iptr, 0, FirstOffsetNumber);
+ RelationUnsetSingleWLockPage (elm->rel, &iptr);
+
+ return (result);
+
+}
+
+
+int4
+currval (struct varlena * seqin)
+{
+ char *seqname = textout(seqin);
+ SeqTable elm;
+ Buffer buf;
+ SequenceTupleForm seq;
+ ItemPointerData iptr;
+ int4 result;
+
+ /* open and WIntentLock sequence */
+ elm = init_sequence ("currval", seqname);
+
+ if ( elm->last != elm->cached ) /* some numbers were cached */
+ {
+ return (elm->last); /* return last returned by nextval */
+ }
+
+ seq = read_info ("currval", elm, &buf);
+
+ if ( seq->is_called != 't' )
+ {
+ elog (WARN, "%s.currval: yet undefined (%s.nextval never called)",
+ seqname, seqname);
+ }
+ result = seq->last_value;
+
+ if ( ReleaseBuffer (buf) == STATUS_ERROR )
+ elog (WARN, "%s.currval: ReleaseBuffer failed", seqname);
+
+ ItemPointerSet(&iptr, 0, FirstOffsetNumber);
+ RelationUnsetSingleWLockPage (elm->rel, &iptr);
+
+ return (result);
+
+}
+
+static SequenceTupleForm
+read_info (char * caller, SeqTable elm, Buffer * buf)
+{
+ ItemPointerData iptr;
+ PageHeader page;
+ ItemId lp;
+ HeapTuple tuple;
+ sequence_magic *sm;
+ SequenceTupleForm seq;
+
+ ItemPointerSet(&iptr, 0, FirstOffsetNumber);
+ RelationSetSingleWLockPage (elm->rel, &iptr);
+
+ if ( RelationGetNumberOfBlocks (elm->rel) != 1 )
+ elog (WARN, "%s.%s: invalid number of blocks in sequence",
+ elm->name, caller);
+
+ *buf = ReadBuffer (elm->rel, 0);
+ if ( !BufferIsValid (*buf) )
+ elog (WARN, "%s.%s: ReadBuffer failed", elm->name, caller);
+
+ page = (PageHeader) BufferGetPage (*buf);
+ sm = (sequence_magic *) PageGetSpecialPointer (page);
+
+ if ( sm->magic != SEQ_MAGIC )
+ elog (WARN, "%s.%s: bad magic (%08X)", elm->name, caller, sm->magic);
+
+ lp = PageGetItemId (page, FirstOffsetNumber);
+ Assert (ItemIdIsUsed (lp));
+ tuple = (HeapTuple) PageGetItem ((Page) page, lp);
+
+ seq = (SequenceTupleForm) GETSTRUCT(tuple);
+
+ elm->increment = seq->increment_by;
+
+ return (seq);
+
+}
+
+
+static SeqTable
+init_sequence (char * caller, char * name)
+{
+ SeqTable elm, priv = (SeqTable) NULL;
+ SeqTable temp;
+
+ for (elm = seqtab; elm != (SeqTable) NULL; )
+ {
+ if ( strcmp (elm->name, name) == 0 )
+ break;
+ priv = elm;
+ elm = elm->next;
+ }
+
+ if ( elm == (SeqTable) NULL ) /* not found */
+ {
+ temp = (SeqTable) malloc (sizeof(SeqTableData));
+ temp->name = malloc (strlen(name) + 1);
+ strcpy (temp->name, name);
+ temp->rel = (Relation) NULL;
+ temp->cached = temp->last = temp->increment = 0;
+ temp->next = (SeqTable) NULL;
+ }
+ else /* found */
+ {
+ if ( elm->rel != (Relation) NULL) /* already opened */
+ return (elm);
+ temp = elm;
+ }
+
+ temp->rel = heap_openr (name);
+
+ if ( ! RelationIsValid (temp->rel) )
+ elog (WARN, "%s.%s: sequence does not exist", name, caller);
+
+ RelationSetWIntentLock (temp->rel);
+
+ if ( temp->rel->rd_rel->relkind != RELKIND_SEQUENCE )
+ elog (WARN, "%s.%s: %s is not sequence !", name, caller, name);
+
+ if ( elm != (SeqTable) NULL ) /* we opened sequence from our */
+ { /* SeqTable - check relid ! */
+ if ( RelationGetRelationId (elm->rel) != elm->relid )
+ {
+ elog (NOTICE, "%s.%s: sequence was re-created",
+ name, caller, name);
+ elm->cached = elm->last = elm->increment = 0;
+ elm->relid = RelationGetRelationId (elm->rel);
+ }
+ }
+ else
+ {
+ elm = temp;
+ elm->relid = RelationGetRelationId (elm->rel);
+ if ( seqtab == (SeqTable) NULL )
+ seqtab = elm;
+ else
+ priv->next = elm;
+ }
+
+ return (elm);
+
+}
+
+
+/*
+ * CloseSequences --
+ * is calling by xact mgr at commit/abort.
+ */
+void
+CloseSequences (void)
+{
+ SeqTable elm;
+ Relation rel;
+
+ ItsSequenceCreation = false;
+
+ for (elm = seqtab; elm != (SeqTable) NULL; )
+ {
+ if ( elm->rel != (Relation) NULL ) /* opened in current xact */
+ {
+ rel = elm->rel;
+ elm->rel = (Relation) NULL;
+ RelationUnsetWIntentLock (rel);
+ heap_close (rel);
+ }
+ elm = elm->next;
+ }
+
+ return;
+
+}
+
+
+static void
+init_params (CreateSeqStmt *seq, SequenceTupleForm new)
+{
+ DefElem *last_value = NULL;
+ DefElem *increment_by = NULL;
+ DefElem *max_value = NULL;
+ DefElem *min_value = NULL;
+ DefElem *cache_value = NULL;
+ List *option;
+
+ new->is_cycled = 'f';
+ foreach (option, seq->options)
+ {
+ DefElem *defel = (DefElem *)lfirst(option);
+
+ if ( !strcasecmp(defel->defname, "increment") )
+ increment_by = defel;
+ else if ( !strcasecmp(defel->defname, "start") )
+ last_value = defel;
+ else if ( !strcasecmp(defel->defname, "maxvalue") )
+ max_value = defel;
+ else if ( !strcasecmp(defel->defname, "minvalue") )
+ min_value = defel;
+ else if ( !strcasecmp(defel->defname, "cache") )
+ cache_value = defel;
+ else if ( !strcasecmp(defel->defname, "cycle") )
+ {
+ if ( defel->arg != (Node*) NULL )
+ elog (WARN, "DefineSequence: CYCLE ??");
+ new->is_cycled = 't';
+ }
+ else
+ elog (WARN, "DefineSequence: option \"%s\" not recognized",
+ defel->defname);
+ }
+
+ if ( increment_by == (DefElem*) NULL ) /* INCREMENT BY */
+ new->increment_by = 1;
+ else if ( ( new->increment_by = get_param (increment_by) ) == 0 )
+ elog (WARN, "DefineSequence: can't INCREMENT by 0");
+
+ if ( max_value == (DefElem*) NULL ) /* MAXVALUE */
+ if ( new->increment_by > 0 )
+ new->max_value = SEQ_MAXVALUE; /* ascending seq */
+ else
+ new->max_value = -1; /* descending seq */
+ else
+ new->max_value = get_param (max_value);
+
+ if ( min_value == (DefElem*) NULL ) /* MINVALUE */
+ if ( new->increment_by > 0 )
+ new->min_value = 1; /* ascending seq */
+ else
+ new->min_value = SEQ_MINVALUE; /* descending seq */
+ else
+ new->min_value = get_param (min_value);
+
+ if ( new->min_value >= new->max_value )
+ elog (WARN, "DefineSequence: MINVALUE (%d) can't be >= MAXVALUE (%d)",
+ new->min_value, new->max_value);
+
+ if ( last_value == (DefElem*) NULL ) /* START WITH */
+ if ( new->increment_by > 0 )
+ new->last_value = new->min_value; /* ascending seq */
+ else
+ new->last_value = new->max_value; /* descending seq */
+ else
+ new->last_value = get_param (last_value);
+
+ if ( new->last_value < new->min_value )
+ elog (WARN, "DefineSequence: START value (%d) can't be < MINVALUE (%d)",
+ new->last_value, new->min_value);
+ if ( new->last_value > new->max_value )
+ elog (WARN, "DefineSequence: START value (%d) can't be > MAXVALUE (%d)",
+ new->last_value, new->max_value);
+
+ if ( cache_value == (DefElem*) NULL ) /* CACHE */
+ new->cache_value = 1;
+ else if ( ( new->cache_value = get_param (cache_value) ) <= 0 )
+ elog (WARN, "DefineSequence: CACHE (%d) can't be <= 0",
+ new->cache_value);
+
+}
+
+
+static int
+get_param (DefElem *def)
+{
+ if ( def->arg == (Node*) NULL )
+ elog (WARN, "DefineSequence: \"%s\" value unspecified", def->defname);
+
+ if ( nodeTag (def->arg) == T_Integer )
+ return (intVal (def->arg));
+
+ elog (WARN, "DefineSequence: \"%s\" is to be integer", def->defname);
+ return (-1);
+}
OSDN Git Service
