diff options
Diffstat (limited to 'src/backend/utils/adt/int.c')
| -rw-r--r-- | src/backend/utils/adt/int.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/src/backend/utils/adt/int.c b/src/backend/utils/adt/int.c index ad8e6d02ee4..04825fc77de 100644 --- a/src/backend/utils/adt/int.c +++ b/src/backend/utils/adt/int.c @@ -30,11 +30,15 @@ #include <ctype.h> #include <limits.h> +#include <math.h> #include "catalog/pg_type.h" #include "common/int.h" #include "funcapi.h" #include "libpq/pqformat.h" +#include "nodes/nodeFuncs.h" +#include "nodes/supportnodes.h" +#include "optimizer/optimizer.h" #include "utils/array.h" #include "utils/builtins.h" @@ -1427,3 +1431,73 @@ generate_series_step_int4(PG_FUNCTION_ARGS) /* do when there is no more left */ SRF_RETURN_DONE(funcctx); } + +/* + * Planner support function for generate_series(int4, int4 [, int4]) + */ +Datum +generate_series_int4_support(PG_FUNCTION_ARGS) +{ + Node *rawreq = (Node *) PG_GETARG_POINTER(0); + Node *ret = NULL; + + if (IsA(rawreq, SupportRequestRows)) + { + /* Try to estimate the number of rows returned */ + SupportRequestRows *req = (SupportRequestRows *) rawreq; + + if (is_funcclause(req->node)) /* be paranoid */ + { + List *args = ((FuncExpr *) req->node)->args; + Node *arg1, + *arg2, + *arg3; + + /* We can use estimated argument values here */ + arg1 = estimate_expression_value(req->root, linitial(args)); + arg2 = estimate_expression_value(req->root, lsecond(args)); + if (list_length(args) >= 3) + arg3 = estimate_expression_value(req->root, lthird(args)); + else + arg3 = NULL; + + /* + * If any argument is constant NULL, we can safely assume that + * zero rows are returned. Otherwise, if they're all non-NULL + * constants, we can calculate the number of rows that will be + * returned. Use double arithmetic to avoid overflow hazards. + */ + if ((IsA(arg1, Const) && + ((Const *) arg1)->constisnull) || + (IsA(arg2, Const) && + ((Const *) arg2)->constisnull) || + (arg3 != NULL && IsA(arg3, Const) && + ((Const *) arg3)->constisnull)) + { + req->rows = 0; + ret = (Node *) req; + } + else if (IsA(arg1, Const) && + IsA(arg2, Const) && + (arg3 == NULL || IsA(arg3, Const))) + { + double start, + finish, + step; + + start = DatumGetInt32(((Const *) arg1)->constvalue); + finish = DatumGetInt32(((Const *) arg2)->constvalue); + step = arg3 ? DatumGetInt32(((Const *) arg3)->constvalue) : 1; + + /* This equation works for either sign of step */ + if (step != 0) + { + req->rows = floor((finish - start + step) / step); + ret = (Node *) req; + } + } + } + } + + PG_RETURN_POINTER(ret); +} |