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authorRobert Haas <rhaas@postgresql.org>2012-02-07 12:41:42 -0500
committerRobert Haas <rhaas@postgresql.org>2012-02-07 12:42:50 -0500
commitf7d7dade8afe19847510efe44be191c35e1ce26c (patch)
tree7fcf4ebc6f73c83acc6875ffc6634581c1c6814b /src/backend/utils/adt/varbit.c
parent3cc0800829a6dda5347497337b0cf43848da4acf (diff)
downloadpostgresql-f7d7dade8afe19847510efe44be191c35e1ce26c.tar.gz
postgresql-f7d7dade8afe19847510efe44be191c35e1ce26c.zip
Add a transform function for varbit typmod coercisions.
This enables ALTER TABLE to skip table and index rebuilds when the new type is unconstraint varbit, or when the allowable number of bits is not decreasing. Noah Misch, with review and a fix for an OID collision by me.
Diffstat (limited to 'src/backend/utils/adt/varbit.c')
-rw-r--r--src/backend/utils/adt/varbit.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/src/backend/utils/adt/varbit.c b/src/backend/utils/adt/varbit.c
index adb08369ed2..1227e5a5082 100644
--- a/src/backend/utils/adt/varbit.c
+++ b/src/backend/utils/adt/varbit.c
@@ -18,6 +18,8 @@
#include "access/htup.h"
#include "libpq/pqformat.h"
+#include "nodes/nodeFuncs.h"
+#include "parser/parse_clause.h"
#include "utils/array.h"
#include "utils/varbit.h"
@@ -646,6 +648,39 @@ varbit_send(PG_FUNCTION_ARGS)
}
/*
+ * varbit_transform()
+ * Flatten calls to our length coercion function that leave the new maximum
+ * length >= the previous maximum length. We ignore the isExplicit argument,
+ * which only affects truncation.
+ */
+Datum
+varbit_transform(PG_FUNCTION_ARGS)
+{
+ FuncExpr *expr = (FuncExpr *) PG_GETARG_POINTER(0);
+ Node *typmod;
+ Node *ret = NULL;
+
+ if (!IsA(expr, FuncExpr))
+ PG_RETURN_POINTER(ret);
+
+ Assert(list_length(expr->args) == 3);
+ typmod = lsecond(expr->args);
+
+ if (IsA(typmod, Const))
+ {
+ Node *source = linitial(expr->args);
+ int32 new_typmod = DatumGetInt32(((Const *) typmod)->constvalue);
+ int32 old_max = exprTypmod(source);
+ int32 new_max = new_typmod;
+
+ if (new_max <= 0 || (old_max >= 0 && old_max <= new_max))
+ ret = relabel_to_typmod(source, new_typmod);
+ }
+
+ PG_RETURN_POINTER(ret);
+}
+
+/*
* varbit()
* Converts a varbit() type to a specific internal length.
* len is the maximum bitlength specified in the column definition.