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Commitf7d7dad

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Add a transform function for varbit typmod coercisions.
This enables ALTER TABLE to skip table and index rebuilds when thenew type is unconstraint varbit, or when the allowable number of bitsis not decreasing.Noah Misch, with review and a fix for an OID collision by me.
1 parent3cc0800 commitf7d7dad

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4 files changed

+40
-2
lines changed

4 files changed

+40
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lines changed

‎src/backend/utils/adt/varbit.c‎

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Original file line numberDiff line numberDiff line change
@@ -18,6 +18,8 @@
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#include"access/htup.h"
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#include"libpq/pqformat.h"
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#include"nodes/nodeFuncs.h"
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#include"parser/parse_clause.h"
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#include"utils/array.h"
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#include"utils/varbit.h"
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@@ -645,6 +647,39 @@ varbit_send(PG_FUNCTION_ARGS)
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PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
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}
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/*
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* varbit_transform()
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* Flatten calls to our length coercion function that leave the new maximum
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* length >= the previous maximum length. We ignore the isExplicit argument,
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* which only affects truncation.
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*/
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Datum
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varbit_transform(PG_FUNCTION_ARGS)
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{
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FuncExpr*expr= (FuncExpr*)PG_GETARG_POINTER(0);
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Node*typmod;
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Node*ret=NULL;
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if (!IsA(expr,FuncExpr))
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PG_RETURN_POINTER(ret);
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Assert(list_length(expr->args)==3);
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typmod=lsecond(expr->args);
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if (IsA(typmod,Const))
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{
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Node*source=linitial(expr->args);
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int32new_typmod=DatumGetInt32(((Const*)typmod)->constvalue);
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int32old_max=exprTypmod(source);
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int32new_max=new_typmod;
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if (new_max <=0|| (old_max >=0&&old_max <=new_max))
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ret=relabel_to_typmod(source,new_typmod);
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}
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PG_RETURN_POINTER(ret);
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}
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/*
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* varbit()
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* Converts a varbit() type to a specific internal length.

‎src/include/catalog/catversion.h‎

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@@ -53,6 +53,6 @@
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*/
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/*yyyymmddN */
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#defineCATALOG_VERSION_NO201202071
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#defineCATALOG_VERSION_NO201202072
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#endif

‎src/include/catalog/pg_proc.h‎

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Original file line numberDiff line numberDiff line change
@@ -2009,7 +2009,9 @@ DESCR("convert bitstring to int4");
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DATA(insertOID=1685 (bitPGNSPPGUID121000ffftfi301560"1560 23 16"_null__null__null__null_bit_null__null__null_ ));
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DESCR("adjust bit() to typmod length");
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DATA(insertOID=1687 (varbitPGNSPPGUID121000ffftfi301562"1562 23 16"_null__null__null__null_varbit_null__null__null_ ));
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DATA(insertOID=3158 (varbit_transformPGNSPPGUID121000ffftfi102281"2281"_null__null__null__null_varbit_transform_null__null__null_ ));
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DESCR("transform a varbit length coercion");
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DATA(insertOID=1687 (varbitPGNSPPGUID121003158ffftfi301562"1562 23 16"_null__null__null__null_varbit_null__null__null_ ));
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DESCR("adjust varbit() to typmod length");
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DATA(insertOID=1698 (positionPGNSPPGUID121000ffftfi2023"1560 1560"_null__null__null__null_bitposition_null__null__null_ ));

‎src/include/utils/varbit.h‎

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Original file line numberDiff line numberDiff line change
@@ -72,6 +72,7 @@ extern Datum varbit_send(PG_FUNCTION_ARGS);
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externDatumvarbittypmodin(PG_FUNCTION_ARGS);
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externDatumvarbittypmodout(PG_FUNCTION_ARGS);
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externDatumbit(PG_FUNCTION_ARGS);
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externDatumvarbit_transform(PG_FUNCTION_ARGS);
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externDatumvarbit(PG_FUNCTION_ARGS);
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externDatumbiteq(PG_FUNCTION_ARGS);
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externDatumbitne(PG_FUNCTION_ARGS);

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