8000 Add a transform function for varbit typmod coercisions. · postgrespro/postgres@f7d7dad · GitHub
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    robertmhaasrobertmhaas
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    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.
    1 parent 3cc0800 commit f7d7dad

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    4 files changed

    +40
    -2
    lines changed

    4 files changed

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    -2
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    ‎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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    1919
    #include "access/htup.h"
    2020
    #include "libpq/pqformat.h"
    21+
    #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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    int32 new_typmod = DatumGetInt32(((Const *) typmod)->constvalue);
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    int32 old_max = exprTypmod(source);
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    int32 new_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

    Lines changed: 1 addition & 1 deletion
    Original file line numberDiff line numberDiff line change
    @@ -53,6 +53,6 @@
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    */
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    /* yyyymmddN */
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    #define CATALOG_VERSION_NO 201202071
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    #define CATALOG_VERSION_NO 201202072
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    #endif

    ‎src/include/catalog/pg_proc.h

    Lines changed: 3 additions & 1 deletion
    Original file line numberDiff line numberDiff line change
    @@ -2009,7 +2009,9 @@ DESCR("convert bitstring to int4");
    20092009

    20102010
    DATA(insert OID = 1685 ( bit PGNSP PGUID 12 1 0 0 0 f f f t f i 3 0 1560 "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(insert OID = 1687 ( varbit PGNSP PGUID 12 1 0 0 0 f f f t f i 3 0 1562 "1562 23 16" _null_ _null_ _null_ _null_ varbit _null_ _null_ _null_ ));
    2012+
    DATA(insert OID = 3158 ( varbit_transform PGNSP PGUID 12 1 0 0 0 f f f t f i 1 0 2281 "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(insert OID = 1687 ( varbit PGNSP PGUID 12 1 0 0 3158 f f f t f i 3 0 1562 "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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    20152017
    DATA(insert OID = 1698 ( position PGNSP PGUID 12 1 0 0 0 f f f t f i 2 0 23 "1560 1560" _null_ _null_ _null_ _null_ bitposition _null_ _null_ _null_ ));

    ‎src/include/utils/varbit.h

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    @@ -72,6 +72,7 @@ extern Datum varbit_send(PG_FUNCTION_ARGS);
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    extern Datum varbittypmodin(PG_FUNCTION_ARGS);
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    extern Datum varbittypmodout(PG_FUNCTION_ARGS);
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    extern Datum bit(PG_FUNCTION_ARGS);
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    extern Datum varbit_transform(PG_FUNCTION_ARGS);
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    extern Datum varbit(PG_FUNCTION_ARGS);
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    extern Datum biteq(PG_FUNCTION_ARGS);
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    extern Datum bitne(PG_FUNCTION_ARGS);

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